title: Data fusion for abundance estimation: community science augments systematically collected removal-in-time distance sampling data

abstract: Ecologists use a variety of systematically and opportunistically sampled count data to estimate bird abundance, and integrating or fusing different datasets has emerged as a critical challenge in recent years. While previous work provides data integration methodology for occupancy (presence/absence) estimation, methods for abundance estimation that account for imperfect detection and disparate survey protocols remains an active area of research. Here we show how to integrate systematically collected removal-in-time distance sampling data from the Integrated Monitoring in Bird Conservation Regions (IMBCR) program with North American Breeding Bird Survey (BBS) point counts and eBird community science observations. Using the Grasshopper Sparrow (Ammodramus savannarum) in the Great Plains of the United States as a focal species, we demonstrate that BBS and eBird data improve predictive performance for IMBCR count data, providing more spatially refined and precise estimates of abundance at regional scales. Data fusion increased predictive performance even despite relatively weak spatial correlations among data sets. The methodology developed here provides a principled way to fuse data when estimating abundance with distance sampling, that accounts for imperfect detection and variable effort.


title: yEvo: Experimental evolution in high school classrooms selects for novel mutations and epistatic interactions that impact clotrimazole resistance in S. cerevisiae.

abstract: Antifungal resistance in pathogenic fungi is a growing global health concern. Non-pathogenic laboratory strains of Saccharomyces cerevisiae are a useful model for studying mechanisms of antifungal resistance that are relevant to understanding the same processes in pathogenic fungi. We developed a series of lab modules in which high school students used experimental evolution to study antifungal resistance by isolating azole-resistant S. cerevisiae and examining the genetic basis of resistance. All 99 sequenced clones from these experiments possessed mutations previously shown to impact azole resistance, demonstrating the efficacy of our protocols. We additionally found recurrent mutations in an mRNA degradation pathway and an uncharacterized mitochondrial protein (Csf1) that have possible mechanistic connections to azole resistance. The scale of replication in this high school-led initiative allowed us to identify epistatic interactions, as evidenced by pairs of mutations that occur in the same clone more frequently than expected by chance (positive epistasis) or less frequently (negative epistasis). We validated one of these pairs, a negative epistatic interaction between gain-of-function mutations in the multidrug resistance transcription factors Pdr1 and Pdr3. This high school-university collaboration can serve as a model for involving members of the broader public in the scientific process to make meaningful discoveries in biomedical research.

category: genetics


title: Distribution of GOPC:ROS1 and other ROS1 fusions in glioma types

abstract: The ROS proto-oncogene 1 (ROS1) gene is rearranged in various cancers. The translated fusion protein presents an attractive therapeutic target, since specific inhibitors have been approved for several tumor types. In glioma, ROS1 fusions are frequent within infantile hemispheric glioma, and single case reports on occurrences in other glioma types exist. However, a comprehensive analysis spanning the full width of glioma types and subtypes is lacking. We here assessed the spectrum and distribution of ROS1 fusions by screening >20,000 glioma cases for typical chromosomal alterations, with subsequent RNA-sequencing for confirmation of candidate cases. ROS1 fusions were identified in 16 cases, from low grade pilocytic astrocytoma WHO grade 1 to glioblastoma, IDH wildtype WHO grade 4. Thus, despite being enriched in some tumor types, ROS1 fusions are not pathognomonic for specific glioma types and may consitute a relevant target in a variety of cases.

category: genomics


title: NOVA2 regulates neural circRNA biogenesis

abstract: Circular RNAs (circRNAs) are highly expressed in the brain and their expression increases during neuronal differentiation. The factors regulating circRNAs in the developing mouse brain are unknown. NOVA1 and NOVA2 are neural-enriched RNA-binding proteins with well-characterized roles in alternative splicing. Profiling of circRNAs from RNA-seq data revealed that global circRNA levels were reduced in embryonic cortex of Nova2 but not Nova1 knockout mice. Analysis of isolated inhibitory and excitatory cortical neurons lacking NOVA2 revealed an even more dramatic reduction of circRNAs and establish a widespread role for NOVA2 in enhancing circRNA biogenesis. To investigate the cis-elements controlling NOVA2-regulation of circRNA biogenesis, we generated a backsplicing reporter based on the Efnb2 gene. We found that NOVA2-mediated backsplicing of circ-Efnb2 was impaired when YCAY clusters located in flanking introns were removed. CLIP and additional reporter analysis demonstrated the importance of NOVA2 binding sites located in both flanking introns of circRNA loci. NOVA2 is the first RNA-binding protein identified to globally promote circRNA biogenesis in the developing brain.


title: Evidence for the equilibrium between monomers and dimers of the death domain of the p75 neurotrophin receptor

abstract: The p75 neurotrophin receptor (p75NTR) is an important mediator of synaptic depression and neuronal cell death, and its expression increases upon nerve injury and in neurodegenerative diseases. However, the molecular mechanisms leading to the activation of this receptor are still a matter of debate. The oligomerization properties of the death domain (DD) of p75NTR are critical for our understanding of the activation mechanisms of the receptor. In this paper, we present additional evidence supporting the existence of an equilibrium between monomeric and dimeric forms of the p75NTR DD in solution and in the absence of any other protein. Dynamic light scattering (DLS) measurements of native, untagged human p75NTR DD at room temperature yielded Rh=2.11 for this domain in 20mM phosphate buffer, corresponding to a molecular weight (MW) of approximately 19kDa, much closer to the theoretical MW of the homodimer (i.e. 21kDa) than the monomer. MWs deduced from the Rh of different control proteins used as standards were all congruent with their theoretical MWs. In addition, size-exclusion FPLC profiles of un-tagged human p75NTR DD in both HEPES and phosphate buffers revealed elution volumes corresponding to a MW of about 15kDa, which is intermediate between monomer and dimer, and indicative of dynamic monomer/dimer interconversion during the run. Together with our previous NMR studies, as well as biophysical data for other investigators, these results support the notion that the DD of p75NTR exists in equilibrium between monomers and dimers in solution, a notion that is in agreement with the oligomerization properties of all members of the DD superfamily.

category: biochemistry


title: A Coupled Flow-Thermoregulation Lumped Model to Investigate Cardiac Function

abstract: AO_SCPLOWBSTRACTC_SCPLOWLumped (zero-dimensional) technique is a robust and widely used approach to mathematically model and explore bulk behaviour of different physical phenomena in a lower expense. In modelling of cardio/cerebrovascular fluid dynamics, this technique facilitates the assessment of relevant metrics such as flow, pressure, and temperature at different locations over a large network/domain. Furthermore, they can be employed as boundary conditions in multiscale modelling of physiological flows. In this methodology paper, a lumped model for the cardiovascular flow simulation along with a two-node thermoregulation model are employed. The lumped models are built upon previous studies and are amended appropriately to focus on cardiac function. The output of the coupled model can either be used for assessing the cardiac function in different physiological conditions or it can provide the input data for other investigations. Noteworthy to mention that, the present model has been specifically developed for investigation on the effects of atrial fibrillation on cardiac performance.

category: bioengineering


title: 3D confinement regulates stem cell fate

abstract: Biophysical properties of the cellular microenvironment, including stiffness and geometry, influence cell fate. Recent findings have implicated geometric confinement as an important regulator of cell fate determination. Our understanding of how mechanical signals direct cell fate is based primarily on two-dimensional (2D) studies. To investigate the role of confinement on stem cell fate in three-dimensional (3D) culture, we fabricated a single cell microwell culture platform and used it to investigate how niche volume and stiffness affect human mesenchymal stem cell (hMSC) fate. The viability and proliferation of hMSCs in confined 3D microniches were compared with the fate of unconfined cells in 2D culture. Physical confinement biased hMSC fate, and this influence was modulated by the niche volume and stiffness. The rate of cell death increased, and proliferation markedly decreased upon 3D confinement. We correlated the observed differences in hMSC fate to YES-associated protein (YAP) localization. In 3D microniches, hMSCs displayed primarily cytoplasmic YAP localization, indicating reduced mechanical activation upon confinement. These results demonstrate that 3D geometric confinement can be an important regulator of cell fate, and that confinement sensing is linked to canonical mechanotransduction pathways.


title: Classification of non-coding variants with high pathogenic impact

abstract: Whole genome sequencing is increasingly used to diagnose medical conditions of genetic origin. While both coding and non-coding DNA variants contribute to a wide range of diseases, most patients who receive a WGS-based diagnosis today harbour a protein-coding mutation. Functional interpretation and prioritization of non-coding variants represents a persistent challenge, and disease-causing non-coding variants remain largely unidentified. Depending on the disease, WGS fails to identify a candidate variant in 20-80% of patients, severely limiting the usefulness of sequencing for personalised medicine. Here we present FINSURF, a machine-learning approach to predict the functional impact of non-coding variants in regulatory regions. FINSURF outperforms state-of-the-art methods, owing to control optimisation during training. In addition to ranking candidate variants, FINSURF also delivers diagnostic information on functional consequences of mutations. We applied FINSURF to a diverse set of 30 diseases with described causative non-coding mutations, and correctly identified the disease-causative non-coding variant within the ten top hits in 22 cases. FINSURF is implemented as an online server to as well as custom browser tracks, and provides a quick and efficient solution to prioritize candidate non-coding variants in realistic clinical settings.

category: bioinformatics


title: Emu: Species-Level Microbial Community Profiling for Full-Length Nanopore 16S Reads

abstract: 16S rRNA based analysis is the established standard for elucidating microbial community composition. While short read 16S analyses are largely confined to genus-level resolution at best since only a portion of the gene is sequenced, full-length 16S sequences have the potential to provide species-level accuracy. However, existing taxonomic identification algorithms are not optimized for the increased read length and error rate of long-read data. Here we present Emu, a novel approach that employs an expectation-maximization (EM) algorithm to generate taxonomic abundance profiles from full-length 16S rRNA reads. Results produced from one simulated data set and two mock communities prove Emu capable of accurate microbial community profiling while obtaining fewer false positives and false negatives than alternative methods. Additionally, we illustrate a real-world application of our new software by comparing clinical sample composition estimates generated by an established whole-genome shotgun sequencing workflow to those returned by full-length 16S sequences processed with Emu.


title: Reconstructing co-dependent cellular crosstalk in lung adenocarcinoma using REMI

abstract: Cellular crosstalk in tissue microenvironments is fundamental to normal and pathological biological processes. Global assessment of cell-cell interactions (CCI) is not yet technically feasible, but computational efforts to reconstruct these interactions have been proposed. Current computational approaches that identify CCI often make the simplifying assumption that pairwise interactions are independent of one another, which can lead to reduced accuracy. We present REMI (REgularized Microenvironment Interactome), a graph-based algorithm that predicts ligand-receptor (LR) interactions by accounting for LR dependencies on high-dimensional, small sample size datasets. We apply REMI to reconstruct the human lung adenocarcinoma (LUAD) interactome from a bulk flow-sorted RNA-seq dataset, then leverage single-cell transcriptomics data to increase its resolution and identify LR prognostic signatures. We experimentally confirmed colocalization of CTGF:LRP6 as an interaction predicted to be associated with LUAD progression. Our work presents a novel way to reconstruct interactomes and a new approach to identify clinically-relevant cell-cell interactions.


title: An Omics Analysis Search and Information System (OASIS) for Enabling Biological Discovery in the Old Order Amish

abstract: The "Omics Analysis Search and Information System" (OASIS), developed at the University of Maryland School of Medicine, enables discovery by allowing researchers to mine results from genome wide association studies (GWAS). When interesting signals are found, the research can immediately ask follow-up questions and get answers in real-time. OASIS provides this unique capability with a web-based, scientist-friendly search system and a variety of real-time analysis tools (linkage disequilibrium calculations, conditional analysis, and direct variant comparison) plus on-demand visualizations (boxplots, histograms, LocusZoom & Haploview plots, and pedigree charts). Because OASIS uses a web-based user interface, an understanding of programming or the UNIX operating system is not required. The OASIS application has been used to enable discovery from whole-exome, whole-genome, metabolome, transcriptome and methylome association results for Old Order Amish studies at the University of Maryland School of Medicine.


title: Scarf: A toolkit for memory efficient analysis of large-scale single-cell genomics data

abstract: The increasing capacity to perform large-scale single-cell genomic experiments continues to outpace the computational requirements to efficiently handle growing datasets. Herein we present Scarf, a modularly designed Python package that seamlessly interoperates with other single-cell toolkits and allows for memory-efficient single-cell analysis of millions of cells on a laptop or low-cost devices like single board computers. We demonstrate Scarfs memory and compute-time efficiency by applying it to the largest existing single-cell RNA-Seq and ATAC-Seq datasets. Scarf wraps memory-efficient implementations of a graph-based t-stochastic neighbour embedding and hierarchical clustering algorithm. Moreover, Scarf performs accurate reference-anchored mapping of datasets while maintaining memory efficiency. By implementing a novel data downsampling algorithm, Scarf additionally can generate representative sampling of cells from a given dataset wherein rare cell populations and lineage differentiation trajectories are conserved. Together, Scarf provides a framework wherein any researcher can perform advanced processing, downsampling, reanalysis, and integration of atlas-scale datasets on standard laptop computers.


title: Muscle fatigue revisited - Insights from optically pumped magnetometers

abstract:
Muscle fatigue is well characterized electromyographically, nevertheless only information about summed potential differences is detectable. In contrast, recently developed quantum sensors optically pumped magnetometers (OPMs) offer the advantage of recording both the electrical current propagation in the muscle as well as its geometry, by measuring the magnetic field generated by the muscular action potentials. Magnetomyographic investigation of muscle fatigue is still lacking and it is an open question whether fatigue is characterized similarly in magnetomyography (MMG) compared to electromyography (EMG). Herein, we investigated the muscle fatigue during a 3x1-min strong isometric contraction of the rectus femoris muscle of 12 healthy subjects using simultaneous EMG-MMG (4-channel surface EMG and 4 OPM along the rectus femoris muscle).

Both EMG and MMG showed the characteristic frequency decrease in the signal magnitude during isometric contraction, which is typical for muscle fatigue. In addition, it was shown that the main part of this frequency decrease seems to occur in the circular component of the magnetic field around the muscle fibers and less longitudinally along the muscle fibers. Overall, these results show not only that magnetomyography is capable of reproducing the electromyographic standards in identifying muscular fatigue, but it also adds relevant information about the spatial characterization of the signal. Therefore, OPM-MMG offers new insights for the study of muscular activity and might serve as a new, supplementary neurophysiological method.

category: physiology


title: The Arabidopsis thaliana PeptideAtlas; harnessing world-wide proteomics data for a comprehensive community proteomics resource

abstract:
We developed a new resource, the Arabidopsis PeptideAtlas (www.peptideatlas.org/builds/arabidopsis/), to solve central questions about the Arabidopsis proteome, such as the significance of protein splice forms, post-translational modifications (PTMs), or simply obtain reliable information about specific proteins. PeptideAtlas is based on published mass spectrometry (MS) analyses collected through ProteomeXchange and reanalyzed through a uniform processing and metadata annotation pipeline. All matched MS-derived peptide data are linked to spectral, technical and biological metadata. Nearly 40 million out of [~]143 million MSMS spectra were matched to the reference genome Araport11, identifying [~]0.5 million unique peptides and 17858 uniquely identified proteins (only isoform per gene) at the highest confidence level (FDR 0.0004; 2 non-nested peptides [≥] 9 aa each), assigned canonical proteins, and 3543 lower confidence proteins. Physicochemical protein properties were evaluated for targeted identification of unobserved proteins. Additional proteins and isoforms currently not in Araport11 were identified, generated from pseudogenes, alternative start, stops and/or splice variants and sORFs; these features should be considered for updates to the Arabidopsis genome. Phosphorylation can be inspected through a sophisticated PTM viewer. This new PeptideAtlas is integrated with community resources including TAIR, tracks in JBrowse, PPDB and UniProtKB. Subsequent PeptideAtlas builds will incorporate millions more MS data.

One sentence summaryA new web resource providing the global community with mass spectrometry-based Arabidopsis proteome information and its spectral, technical and biological metadata integrated with TAIR and JBrowse

category: plant biology


title: Potential role of Aphidius ervi in protecting greenhouse bell pepper cultures from Myzus persicae aphids in India

abstract: Many aphids such as Myzus persicae are major agricultural pest against which sustainable solutions must be developed. In the present study, we evaluated the role of Aphidius ervi (Hymenoptera: Braconidae), an aphid parasitoid, to control M. persicae in bell pepper cultures in greenhouses. Parasitoids were released at one occasion in a greenhouse and M. persicae infested plants were followed before and after parasitoid introduction. We evaluated aphid numbers and parasitism rates at two different controlled temperatures (22{degrees}C and 25{degrees}C), and we measured diapause levels in released parasitoids. Aphidius ervi showed parasitism rates of 10.9{+/-}1.2% and 9.1{+/-}1.6%, at 21 and 25{degrees}C, respectively. The strain of parasitoids we used was not entering diapause under any temperature condition. Therefore, we suggest that A. ervi can be further investigated as a protection in greenhouse environments in India. More releases may be necessary to achieve a good protection.


title: Simple and efficient heterologous expression of necrosis-inducing effectors using the model plant Nicotiana benthamiana

abstract: Plant fungal pathogens cause devastating diseases on cereal plants and threaten global food security. During infection, these pathogens secrete proteinaceous effectors that promote disease. Some of these effectors from necrotrophic plant pathogens induce a cell death response (necrosis), which facilitates pathogen growth in planta. Characterisation of these effectors typically requires heterologous expression and microbial expression systems such as bacteria and yeast are the predominantly used. However, microbial expression systems often require optimization for any given effector and are, in general, not suitable for effectors involving cysteine bridges and posttranslational modifications for activity. Here, we describe a simple and efficient method for expressing such effectors in the model plant Nicotiana benthamiana. Briefly, an effector protein is transiently expressed and secreted into the apoplast of N. benthamiana by Agrobacterium-mediated infiltration. Two-to-three days subsequent to agroinfiltration, the apoplast from the infiltrated leaves is extracted and can be directly used for phenotyping on host plants. The efficacy of this approach was demonstrated by expressing the ToxA, Tox3 and Tox1 necrosis-inducing effectors from Parastagonospora nodorum. All three effectors produced in N. benthamiana were capable of inducing necrosis in wheat lines, and two of three showed visible bands on Coomassie-stained gel. These data suggest that N. benthamiana-agroinfiltration system is a feasible tool to obtain fungal effectors, especially those that require disulfide bonds and posttranslational modifications. Furthermore, due to the low number of proteins typically observed in the apoplast (compared to intracellular), this simple and high-throughput approach circumvents the requirement to lyse cells and further purify the target proteins that is required in other heterologous systems. Because of its simplicity and potential for high-throughput, this method is highly amenable to the phenotyping of candidate protein effectors on host plants.


title: Neuronal genetic rescue normalizes brain network dynamics in a lysosomal storage disorder despite persistent storage accumulation

abstract: Although neurologic symptoms occur in two-thirds of lysosomal storage disorders (LSDs), for most we do not understand the mechanisms underlying brain dysfunction. A major unanswered question is if the pathogenic hallmark of LSDs, storage accumulation, induces functional defects directly or is a disease bystander. Also, for most LSDs we do not know the impact of loss-of-function in individual cell types. Understanding these critical questions are essential to therapy development. Here, we determined the impact of genetic rescue in distinct cell types on neural circuit dysfunction in CLN3 disease, the most common pediatric dementia and a representative LSD. We restored Cln3 expression via AAV-mediated gene delivery and conditional genetic rescue in a CLN3 mouse model. Surprisingly, we found that low-level rescue of Cln3 expression in neurons alone normalized clinically-relevant electrophysiologic markers of network dysfunction, despite the presence of substantial residual histopathology, in contrast to restoring expression in astrocytes. Thus, loss of Cln3 function in neurons, not storage accumulation, underlies neurologic dysfunction in CLN3 disease, implying that storage clearance may be an inappropriate target for therapy development and an ineffectual biomarker.

category: neuroscience


title: Synaptic control of temporal processing in the Drosophila olfactory system

abstract: Temporal filtering of sensory stimuli is a key neural computation, but the way such filters are implemented within the brain is unclear. One potential mechanism for implementing temporal filters is short-term synaptic plasticity, which is governed in part by the expression of pre-synaptic proteins that position synaptic vesicles at different distances to calcium channels. Here we leveraged the Drosophila olfactory system to directly test the hypothesis that short-term synaptic plasticity shapes temporal filtering of sensory stimuli. We used optogenetic activation to drive olfactory receptor neuron (ORN) activity with high temporal precision and knocked down the presynaptic priming factor unc13A specifically in ORNs. We found that this manipulation specifically decreases and delays transmission of high frequencies, leading to poorer encoding of distant plume filaments. We replicate this effect using a previously-developed model of transmission at this synapse, which features two components with different depression kinetics. Finally, we show that upwind running, a key component of odor source localization, is preferentially driven by high-frequency stimulus fluctuations, and this response is reduced by unc13A knock-down in ORNs. Our work links the extraction of particular temporal features of a sensory stimulus to the expression of particular presynaptic molecules.


title: Pipeline for 4D whole-brain microscopy preprocessing and analysis.

abstract: Acute stress leads to sequential activation of functional brain networks. The challenge is to get insight in whole brain activity at multiple scales, beyond the level of (networks of) nuclei. We developed a novel pre-processing and analytical pipeline to chart whole-brain immediate early genes expression - as proxy for cellular activity - after a single stressful foot-shock in 4 dimensions; that is, from functional networks up to 3D single-cell resolution, and over time. The pipeline is available as R-package. Most brain areas (96%) showed increased numbers of c-fos+ cells after foot-shock, yet hypothalamic areas stood out as being most active and prompt in their activation, followed by amygdalar, prefrontal, hippocampal and finally thalamic areas. At the cellular level, c-fos+ density clearly shifted over time across subareas, as illustrated for the basolateral amygdala. Moreover, some brain areas showed increased numbers of c-fos+ cells, while others dramatically increased c-fos intensity in just a subset of cells; this  strategy changed after foot-shock in half of the brain areas. All single-cell data can be visualized for each of the 90 brain areas examined through our interactive web-portal.


title: The mouse brain after foot-shock in 4D: temporal dynamics at a single cell resolution


title: Integration, coincidence detection and resonance in networks of spiking neurons expressing gamma oscillations and asynchronous states

abstract:
Gamma oscillations are widely seen in the awake and sleeping cerebral cortex, but the exact role of these oscillations is still debated. Here, we used biophysical models to examine how gamma oscillations may participate to the processing of afferent stimuli. We constructed conductance-based network models of gamma oscillations, based on different cell types found in cerebral cortex. The models were adjusted to extracellular unit recordings in humans, where gamma oscillations always coexist with the asynchronous firing mode. We considered three different mechanisms to generate gamma, first a mechanism based on the interaction between pyramidal neurons and interneurons (PING), second a mechanism in which gamma is generated in interneuron networks (ING) and third, a mechanism which relies on gamma oscillations generated by pacemaker chattering neurons (CHING). We find that all three mechanisms generate features consistent with human recordings, but that the ING mechanism is most consistent with the firing rate change inside Gamma bursts seen in the human data. We next evaluated the responsiveness and resonant properties of these networks, contrasting gamma oscillations with the asynchronous mode. We find that for both slowly-varying stimuli and precisely-timed stimuli, the responsiveness is generally lower during Gamma compared to asynchronous states, while resonant properties are similar around the Gamma band. We could not find conditions where Gamma oscillations were more responsive. We therefore predict that asynchronous states provide the highest responsiveness to external stimuli, while Gamma oscillations tend to overall diminish responsiveness.

Author summaryIn the awake and attentive brain, the activity of neurons is typically asynchronous and irregular. It also occasionally displays oscillations in the Gamma frequency range (30-90 Hz), which are believed to be involved in information processing. Here, we use computational models to investigate how brain circuits generate oscillations in a manner consistent with microelectrode recordings in humans. We then study how these networks respond to external input, comparing asynchronous and oscillatory states. This is tested according to several paradigms, an integrative mode, where slowly varying inputs are progressively integrated, a coincidence detection mode, where brief inputs are processed according to the phase of the oscillations, and a resonance mode where the network is probed with oscillatory inputs. Surprisingly, we find that in all cases, the presence of Gamma oscillations tends to diminish the responsiveness to external inputs, and we found no paradigm by which Gamma oscillations would favor information flow compared to asynchronous states. We discuss possible implications of this responsiveness decrease on information processing and propose new directions for further exploration.


title: Correction of amblyopia in cats and mice after the critical period

abstract: Monocular deprivation early in development causes amblyopia, a severe visual impairment. Prognosis is poor if therapy is initiated after an early critical period. However, clinical observations have shown that recovery from amblyopia can occur later in life when the non-deprived (fellow) eye is removed. The traditional interpretation of this finding is that vision is improved by relieving interocular suppression in primary visual cortex. However, an alternative explanation is that elimination of activity in the fellow eye establishes conditions in visual cortex that enable the weak connections from the amblyopic eye to gain strength. Here we show in cats and mice that temporary inactivation of the fellow eye is sufficient to promote a full and enduring recovery from amblyopia at ages when conventional treatments fail. Thus, connections serving the amblyopic eye are capable of substantial plasticity beyond the critical period, and this potential is unleashed by reversibly silencing the fellow eye.


title: In amygdala we trust: different contributions of the basolateral and central amygdala in learning whom to trust

abstract:
Human societies are built on cooperation and mutual trust, but not everybody is trustworthy. Research on rodents suggests an essential role of the basolateral amygdala (BLA) in learning from social experiences (Hernandez-Lallement J et al., 2016), which was also confirmed in human subjects with selective bilateral BLA damage as they failed to adapt their trust behavior towards trustworthy vs. untrustworthy interaction partners (Rosenberger LA et al., 2019). However, neuroimaging in neurotypical populations did not consistently report involvement of the amygdala in trust behavior. This might be explained by the difficulty of differentiating between amygdalas structurally and functionally different subnuclei, i.e., the BLA and central amygdala (CeA), which have even antagonistic features particularly in trust behavior (van Honk J et al., 2013). Here, we used fMRI of the amygdala subnuclei of neurotypical adults (n=31f/31m) engaging in the repeated trust game. Our data show that both the BLA and the CeA play a role and indeed differentially: While the BLA was most active when obtaining feedback on whether invested trust had been reciprocated or not, the CeA was most active when subjects were preparing their next trust decision. In the latter phase, improved learning was associated with higher activation differences in response to untrustworthy vs. trustworthy trustees, in both BLA and CeA. Our data not only translate to rodent models and support our earlier findings in BLA-damaged subjects, but also show the specific contributions of other brain structures in the amygdala-centered network in learning whom to trust, and better not to trust.

SIGNIFICANCE STATEMENTIn this fMRI study, the central amygdala was found active during trust behavior planning, while the basolateral amygdala was active during outcome evaluation. When planning trust behavior, central and basolateral amygdala activation differences between the players was related to whether participants learned to differentiate the players trustworthiness. Nucleus accumbens tracked whether trust was reciprocated but was not related to learning. This suggests learning whom to trust is not related to reward processing in the nucleus accumbens but rather to engagement of the basolateral amygdala. This study overcomes major empirical gaps between animal models and human neuroimaging and shows how different amygdala subnuclei and connected areas orchestrate learning to form different subjective trustworthiness beliefs about others and guide trust choice behavior.


title: Gated recurrence enables simple and accurate sequence prediction in stochastic, changing, and structured environments

abstract: From decision making to perception to language, predicting what is coming next is crucial. It is also challenging in stochastic, changing, and structured environments; yet the brain makes accurate predictions in many situations. What computational architecture could enable this feat? Bayesian inference makes optimal predictions but is prohibitively difficult to compute. Here, we show that a specific recurrent neural network architecture enables simple and accurate solutions in several environments. This architecture relies on three mechanisms: gating, lateral connections, and recurrent weight training. Like the optimal solution and the human brain, such networks develop internal representations of their changing environment (including estimates of the environments latent variables and the precision of these estimates), leverage multiple levels of latent structure, and adapt their effective learning rate to changes without changing their connection weights. Being ubiquitous in the brain, gated recurrence could therefore serve as a generic building block to predict in real-life environments.


title: Repeated administration of 2-hydroxypropyl-β-cyclodextrin (HPβCD) attenuates the chronic inflammatory response to experimental stroke

abstract:
Globally, more than 67 million people are living with the effects of ischemic stroke. Importantly, many stroke survivors develop a chronic inflammatory response that may contribute to cognitive impairment, a common and debilitating sequela of stroke that is insufficiently studied and currently untreatable. 2-hydroxypropyl-{beta}-cyclodextrin (HP{beta}CD) is an FDA-approved cyclic oligosaccharide that can solubilize and entrap lipophilic substances. The goal of the present study was to determine whether the repeated administration of HP{beta}CD curtails the chronic inflammatory response to stroke by reducing lipid accumulation within stroke infarcts in a distal middle cerebral artery occlusion mouse model of stroke. To achieve this goal, we subcutaneously injected young adult and aged male mice with vehicle or HP{beta}CD three times per week, with treatment beginning one week after stroke. We evaluated mice at 7 weeks following stroke using immunostaining, RNA sequencing, lipidomics, and behavioral analyses. Chronic stroke infarct and peri-infarct regions of HP{beta}CD-treated mice were characterized by an upregulation of genes involved in lipid metabolism and a downregulation of genes involved in innate and adaptive immunity, reactive astrogliosis, and chemotaxis. Correspondingly, HP{beta}CD reduced the accumulation of lipid droplets, T lymphocytes, B lymphocytes, and plasma cells in stroke infarcts. Repeated administration of HP{beta}CD also preserved NeuN immunoreactivity in the striatum and thalamus and c-Fos immunoreactivity in hippocampal regions. Additionally, HP{beta}CD improved recovery through the protection of hippocampal-dependent spatial working memory and reduction of impulsivity. These results indicate that systemic HP{beta}CD treatment following stroke attenuates chronic inflammation and secondary neurodegeneration and prevents post-stroke cognitive decline.

Significance StatementDementia is a common and debilitating sequela of stroke. Currently, there are no available treatments for post-stroke dementia. Our study shows that lipid metabolism is disrupted in chronic stroke infarcts, which causes an accumulation of uncleared lipid debris and correlates with a chronic inflammatory response. To our knowledge, these substantial changes in lipid homeostasis have not been previously recognized or investigated in the context of ischemic stroke. We also provide a proof of principle that solubilizing and entrapping lipophilic substances using HP{beta}CD could be an effective strategy for treating chronic inflammation after stroke and other CNS injuries. We propose that using HP{beta}CD for the prevention of post-stroke dementia could improve recovery and increase long-term quality of life in stroke sufferers.


title: A theory of direction selectivity for Macaque primary visual cortex

abstract:
This paper offers a new theory for the origin of direction selectivity in the Macaque primary visual cortex, V1. Direction selectivity (DS) is essential for the perception of motion and control of pursuit eye movements. In the Macaque visual pathway, DS neurons first appear in V1, in the Simple cell population of the Magnocellular input layer 4C. The LGN cells that project to these cortical neurons, however, are not direction-selective. We hypothesize that DS is initiated in feedforward LGN input, in the summed responses of LGN cells afferent to a cortical cell, and it is achieved through the interplay of (a) different visual response dynamics of ON and OFF LGN cells, and (b) the wiring of ON and OFF LGN neurons to cortex. We identify specific temporal differences in the ON/OFF pathways that together with (b) produce distinct response time-courses in separated subregions; analysis and simulations confirm the efficacy of the mechanisms proposed. To constrain the theory, we present data on Simple cells in layer 4C in response to drifting gratings. About half of the cells were found to have high DS, and the DS was broad-band in spatial and temporal frequency (SF and TF). The proposed theory includes a complete analysis of how stimulus features such as SF and TF interact with ON/OFF dynamics and LGN-to-cortex wiring to determine the preferred direction and magnitude of DS.

Significance StatementMotion perception is important for primates, and direction selectivity (DS), the ability to perceive the direction a target is moving, is an essential part of motion perception. Yet no satisfactory mechanistic explanation has been proposed for the origin of DS in primate visual cortex up until now. In this paper, we hypothesize that DS is initiated in feedforward LGN input as a result of the dynamic differences between the ON/OFF pathways. The mechanisms we propose are biology-based, and our theory explains experimental data for all spatial and temporal frequencies in visual stimuli. Exploiting temporal biases in parallel pathways is relevant beyond visual neuroscience; similar ideas likely apply to other types of neural signal processing.g


title: Basal forebrain cholinergic neurons are part of the threat memory engram

abstract: Although the engagement of cholinergic signaling in threat memory is well established (Knox, 2016a), our finding that specific cholinergic neurons are requisite partners in a threat memory engram is likely to surprise many. Neurons of the basal forebrain nucleus basalis and substantia innominata (NBM/SIp) comprise the major source of cholinergic input to the basolateral amygdala (BLA), whose activation are required for both the acquisition and retrieval of cued threat memory and innate threat response behavior. The retrieval of threat memory by the presentation of the conditioning tone alone elicits acetylcholine (ACh) release in the BLA and the BLA-projecting cholinergic neurons manifest immediate early gene responses and display increased intrinsic excitability for 2-5 hours following the cue-elicited memory response to the conditioned stimulus. Silencing cue-associated engram-enrolled cholinergic neurons prevents the expression of the defensive response and the subset of cholinergic neurons activated by cue is distinct from those engaged by innate threat. Taken together we find that distinct populations of cholinergic neurons are recruited to signal distinct aversive stimuli via the BLA, demonstrating exquisite, functionally refined organization of specific types of memory within the cholinergic basal forebrain.


title: Chicoric acid prevents neurodegeneration via microbiota-gut-brain axis in a mouse Parkinson's disease model

abstract: It is determined that microbiota-gut-brain axis is involved in the pathogenesis of Parkinsons Disease (PD) and may be the potential target for developing the therapeutic treatments for PD. Chicoric acid (CA) is a kind of natural polyphenolic acid compounds which are recognized as promising agents against neurodegenerative disease. Here, we investigated the influence of CA on microbiota-gut-brain axis in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mice. The results demonstrated that oral pretreatments of CA significantly prevented the MPTP-indued motor disorders, death of nigrostriatal dopaminergic neurons and reduction in striatal neurotrophins. Sequencing results of 16S rRNA indicated the microbial dysbiosis occurred in MPTP mice, whereas CA exerted a remarkable impact on microbial diversity and microbiota compositions, as well as SCFAs production. Besides, CA pretreatment alleviated gliosis-mediated neuroinflammation and gut inflammation by suppressing TLR4/MyD88/NF-{kappa}B signaling cascade, along with preventing the colonic hyperpermeability. To conclude, CA prevented MPTP-induced neuroinflammation and neuronal degenerative processes through signaling multiple pathways of microbiota-gut-brain axis.


title: Sex-specific multi-level 3D genome dynamics in the mouse brain

abstract: The female mammalian brain exhibits sex-hormone-driven plasticity during the reproductive period. Evidence implicates chromatin dynamics in gene regulation underlying this plasticity. However, whether ovarian hormones impact higher-order chromatin organization in post-mitotic neurons in vivo is unknown. Here, we mapped 3D genome of ventral hippocampal neurons across the estrous cycle and by sex in mice. In females, we found cycle-driven dynamism in 3D chromatin organization, including in estrogen-response-elements-enriched X-chromosome compartments, autosomal CTCF loops, and enhancer-promoter interactions. With rising estrogen levels, the female 3D genome becomes more similar to the male genome. Cyclical enhancer-promoter interactions are partially associated with gene expression and enriched for brain disorder-relevant genes. Our study reveals unique 3D genome dynamics in the female brain relevant to female-specific gene regulation, neuroplasticity, and disease risk.


title: Metagenomics and Metatranscriptomics Reveal Pathway of 3-Chloroaniline Degradation in Wastewater Reactors

abstract: Biological wastewater treatment systems are often affected by major shifts in influent quality, including the input of various toxic chemicals. Yet the mechanisms underlying adaptation of activated sludge process performance when challenged with a sustained toxin input have not been studied in a controlled and replicated experiment. Three replicate bench-scale bioreactors were subjected to a chemical disturbance in the form of 3-chloroaniline (3-CA) input over 132 days, following an acclimation period of 58 days, while three control reactors received no 3-CA input. The nitrification process was initially affected by 3-CA input; yet all three treatment reactors evolved to biologically degrade 3-CA within three weeks of the experiment, resulting in partial nitrification recovery. 16S rRNA amplicon sequencing revealed that ammonia oxidizers were initially impacted by 3-CA, and a new ammonia oxidizing community emerged with the onset of 3-CA degradation. Combining process and microbial community data from amplicon sequencing with potential functions gleaned from assembled metagenomics and metatranscriptomics data, 3-CA degradation was shown to likely occur via a phenol monooxygenase followed by ortho-cleavage of the aromatic ring. The relative abundance of genera Gemmatimonas, Saprospiraceae OLB8 and Taibaiella correlated significantly with 3-CA degradation. This study demonstrated the impact of a sustained stress on the activated sludge community and wastewater treatment process and its subsequent recovery. Using a combination of techniques in a controlled and replicated experiment, we showed that microbial communities can evolve degradative capacity following a sustained xenobiotic input, specific functions like nitrification can fully or partially recover and targeted culture-independent approaches can be used to elucidate the mechanisms of adaptation.

category: microbiology


title: Small-molecule modulators of TRMT2A decrease PolyQ aggregation and PolyQ-induced cell death

abstract: Polyglutamine (polyQ) diseases are characterized by an expansion of cytosine-adenine-guanine (CAG) trinucleotide repeats encoding for an uninterrupted prolonged polyQ tract. We previously identified TRMT2A as a strong modifier of polyQ-induced toxicity in an unbiased large-scale screen in Drosophila melanogaster. This work aimed at identifying and validating pharmacological TRMT2A inhibitors as treatment opportunities for polyQ diseases in humans. Computer-aided drug discovery was implemented to identify human TRMT2A inhibitors. Additionally, the crystal structure of one protein domain, the RNA recognition motif (RRM), was determined, and Biacore experiments with the RRM were performed. The identified molecules were validated for their potency to reduce polyQ aggregation and polyQ-induced cell death in human HEK293T cells and patient derived fibroblasts. Our work provides a first step towards pharmacological inhibition of this enzyme and indicates TRMT2A as a viable drug target for polyQ diseases.

category: molecular biology


title: Meiosis-Specific Cohesin Complexes Display Distinct and Essential Roles in Mitotic ESC Chromosomes

abstract: Cohesin is a chromosome-associated SMC-kleisin complex that mediates sister chromatid cohesion, recombination, and most chromosomal processes during mitosis and meiosis. Through high-resolution 3D-structured illumination microscopy and functional analyses, we report multiple biological processes associated with the meiosis-specific cohesin components, REC8 and STAG3, and the distinct loss of function of meiotic cohesin during the cell cycle of embryonic stem cells (ESCs). First, we show that REC8 is translocated into the nucleus in a STAG3-dependent manner. REC8/STAG3-containing cohesin regulates chromosome topological properties and specifically maintains centromeric cohesion. Second, REC8 and mitotic cohesin RAD21 are located at adjacent sites but predominantly at nonoverlapping sites on ESC chromosomes, implying that REC8 can function independent of RAD21 in ESCs. Third, knockdown of REC8-cohesin not only leads to higher rates of premature centromere separation and stalled replication forks, which can cause proliferation and developmental defects, but also enhances compaction of the chromosome structure by hyperloading of retinoblastoma protein-condensin complexes from prophase onward. We propose that the delicate balance between mitotic and meiotic cohesins may regulate ESC- specific chromosomal organization and mitotic program.


title: Human iPSC-derived brain endothelial microvessels in a multi-well format enable permeability screens of anti-inflammatory drugs

abstract: Optimizing drug candidates for blood-brain barrier (BBB) penetration in humans remains one of the key challenges and many devastating brain diseases including neurodegenerative diseases still do not have adequate treatments. So far, it has been difficult to establish state-of-the-art human stem cell derived in vitro models that mimic physiological barrier properties including a 3D microvasculature in a format that is scalable enough to screen drugs for BBB penetration in early drug development phases. To address this challenge, we established human induced pluripotent stem cell (iPSC)-derived brain endothelial microvessels in a standardized and scalable multi-well plate format. iPSC-derived brain microvascular endothelial cells (BMECs) were supplemented with primary cell conditioned media and grew to intact microvessels in 10 days of culturing. Produced microvessels show a typical BBB phenotype including endothelial protein expression, tight-junctions and polarized localization of efflux transporter. Microvessels exhibited physiological relevant trans-endothelial electrical resistance (TEER), were leak-tight for 10 kDa dextran-Alexa 647 and strongly limited the permeability of sodium fluorescein (NaF). Permeability tests with reference compounds confirmed the suitability of our model as platform to identify potential BBB penetrating anti-inflammatory drugs. In summary, the here presented brain microvessel platform recapitulates physiological properties and allows rapid screening of BBB permeable anti-inflammatory compounds that has been suggested as promising substances to cure so far untreatable neurodegenerative diseases.

category: cell biology


title: Hepatic mTORC1 signaling activates ATF4 as part of its metabolic response to feeding and insulin

abstract:
ObjectiveThe mechanistic target of rapamycin complex 1 (mTORC1) is dynamically regulated by fasting and feeding cycles in the liver to promote protein and lipid synthesis while suppressing autophagy. However, beyond these functions, the metabolic response of the liver to feeding and insulin signaling orchestrated by mTORC1 remains poorly defined. Here, we determine whether ATF4, a stress responsive transcription factor recently found to be independently regulated by mTORC1 signaling in proliferating cells, is responsive to hepatic mTORC1 signaling to alter hepatocyte metabolism.

MethodsATF4 protein levels and expression of canonical gene targets were analyzed in the liver following fasting and physiological feeding in the presence or absence of the mTORC1 inhibitor rapamycin. Primary hepatocytes from wild-type or liver-specific Atf4 knockout (LAtf4KO) mice were used to characterize the effects of insulin-stimulated mTORC1-ATF4 function on hepatocyte gene expression and metabolism. Both unbiased steady-state metabolomics and stable-isotope tracing methods were employed to define mTORC1 and ATF4-dependent metabolic changes. RNA-sequencing was used to determine global changes in feeding-induced transcripts in the livers of wild-type versus LAtf4KO mice.

ResultsWe demonstrate that ATF4 and its metabolic gene targets are stimulated by mTORC1 signaling in the liver in response to feeding and in a hepatocyte-intrinsic manner by insulin. While we demonstrate that de novo purine and pyrimidine synthesis is stimulated by insulin through mTORC1 signaling in primary hepatocytes, this regulation was independent of ATF4. Metabolomics and metabolite tracing studies revealed that insulin-mTORC1-ATF4 signaling stimulates pathways of non-essential amino acid synthesis in primary hepatocytes, including those of alanine, aspartate, methionine, and cysteine, but not serine.

ConclusionThe results demonstrate that ATF4 is a novel metabolic effector of mTORC1 in liver, extending the molecular consequences of feeding and insulin-induced mTORC1 signaling in this key metabolic tissue to the control of amino acid metabolism.


title: Giant ankyrin-B mediates transduction of axon guidance and collateral branch pruning factor Sema 3A

abstract: Variants in the high confident autism spectrum disorder gene ANK2 target both ubiquitously expressed 220-kDa ankyrin-B and neurospecific 440-kDa ankyrin-B (AnkB440) isoforms. Previous work showed that knock-in mice expressing an ASD-linked Ank2 variant yielding a truncated AnkB440 product exhibit ectopic brain connectivity and behavioral abnormalities. Expression of this variant or loss of AnkB440 caused axonal hyperbranching in vitro, which implicated AnkB440 microtubule bundling activity in suppressing collateral branch formation. Leveraging multiple mouse models, cellular assays, and live microscopy, we show that AnkB440 also modulates axon collateral branching stochastically by reducing the number of F-actin-rich branch initiation points. Additionally, we show that AnkB440 enables growth cone (GC) collapse in response to chemorepellent factor semaphorin 3A (Sema 3A) by stabilizing its receptor complex L1 cell adhesion molecule/neuropilin-1. ASD-linked ANK2 variants failed to rescue Sema 3A-induced GC collapse. We propose that impaired response to repellent cues due to AnkB440 deficits leads to axonal guidance and branch pruning defects and may contribute to the pathogenicity of ANK2 variants.


title: The PPLD has advantages over conventional regression methods in application to moderately sized genome-wide association studies

abstract: In earlier work, we have developed and evaluated an alternative approach to the analysis of GWAS data, based on a statistic called the PPLD. More recently, motivated by a GWAS for genetic modifiers of the X-linked Mendelian disorder Duchenne Muscular Dystrophy (DMD), we adapted the PPLD for application to time-to-event (TE) phenotypes. Because DMD itself is relatively rare, this is a setting in which the very large sample sizes generally assembled for GWAS are simply not attainable. For this reason, statistical methods specially adapted for use in small data sets are required. Here we explore the behavior of the TE-PPLD via simulations, comparing the TE-PPLD with Cox Proportional Hazards analysis in the context of small to moderate sample sizes. Our results will help to inform our approach to the DMD study going forward, and they illustrate several respects in which the TE-PPLD, and by extension the original PPLD, offer advantages over regression-based approaches to GWAS in this context.


title: Multi-omics prediction of oat agronomic and seed nutritional traits across environments and in distantly related populations

abstract: Multi-omics prediction has been shown to be superior to genomic prediction with genome-wide DNA-based genetic markers (G) for predicting phenotypes. However, most of the existing studies were based on historical datasets from one environment; therefore, they were unable to evaluate the efficiency of multi-omics prediction in multi-environment trials and distantly-related populations. To fill those gaps, we designed a systematic experiment to collect omics data and evaluate 17 traits in two oat breeding populations planted in single and multiple environments. In the single-environment trial, transcriptomic BLUP (T), metabolomic BLUP (M), G+T, G+M and G+T+M models showed greater prediction accuracy than GBLUP for 5, 10, 11, 17 and 17 traits, respectively, and metabolites generally performed better than transcripts when combined with SNPs. In the multi-environment trial, multi-trait models with omics data outperformed both counterpart multi-trait GBLUP models and single-environment omics models, and the highest prediction accuracy was achieved when modeling genetic covariance as an unstructured covariance model. We also demonstrated that omics data can be used to prioritize loci from one population with omics data to improve genomic prediction in a distantly-related population using a two-kernel linear model that accommodated both likely casual loci with large-effect and loci that explain little or no phenotypic variance. We propose that the two-kernel linear model is superior to most genomic prediction models that assume each variant is equally likely to affect the trait and can be used to improve prediction accuracy for any trait with prior knowledge of genetic architecture.


title: Cryo-EM structures of the Caspase activated protein XKR9 involved in apoptotic lipid scrambling

abstract: The exposure of the negatively charged lipid phosphatidylserine on the cell-surface, catalyzed by lipid scramblases, is an important signal for the clearance of apoptotic cells by macrophages. The protein XKR9 is a member of a conserved family that has been associated with apoptotic lipid scrambling. Here, we describe structures of full-length and caspase-treated XKR9 in complex with a synthetic nanobody determined by cryo-electron microscopy. The 43 kDa monomeric membrane protein contains eight membrane-spanning helices, two segments that are partly inserted into the lipid bilayer and is organized as two structurally related repeats. In the full-length protein, the C-terminus interacts with a hydrophobic site located at the intracellular side acting as an inhibitor of protein function. Cleavage by caspase-3 at a specific site releases 16 residues of the C-terminus thus making the binding site accessible to the cytoplasm. Collectively, the work has revealed the unknown architecture of the XKR family and has provided initial insight into its activation by caspases.

category: biophysics


title: Single-molecule mechanical unfolding kinetics of unmodified Saccharomyces cerevisiae tRNAPhe: a hint to the tRNA chaperone-tRNA interaction mechanism

abstract: The biological activity of tRNA is closely related to its mechanical folding properties. Although previous studies focused on the folding and unfolding mechanism of tRNA, its kinetics are largely unknown. In this study, combining optical tweezers and molecule dynamics simulations, we characterized the mechanical folding and unfolding processes of a single unmodified Saccharomyces cerevisiae tRNAphe. We identified the intermediates and pathways for tRNA mechanical folding and unfolding in the presence of Mg2+, discovering that the folding/unfolding kinetics of D stem-loop and T stem-loop but not the anti-codon stem-loop significantly affected by their upstream and downstream structures. The cooperative unfolding of the tRNA in the presence of Mg2+ lead to a large hysteresis between the folding and unfolding pathway, and such hysteresis and unfolding cooperativity are significantly reduced by lowering the Mg2+ concentration or mutating the nucleotides forming the  elbow structure. Moreover, both steered molecular dynamics simulation and optical tweezers experiment results support that, formation of tertiary interactions in the elbow region increases energy barriers of the mechanical unfolding pathway, including those in between intermediates, and determines the overall unfolding cooperativity. Our studies may shed light on the detailed tRNA chaperone mechanism of TruB and TrmA.


title: The oncogenic Runx3-Myc axis defines p53-deficient osteosarcomagenesis

abstract: Osteosarcoma (OS) in human patients is characterized by genetic alteration of TP53. Osteoprogenitor-specific p53-deleted mice (OS mice) have been widely used to study the process of osteosarcomagenesis. However, the molecular mechanisms responsible for the development of OS upon p53 inactivation remain largely unknown. In this study, we detected prominent RUNX3/Runx3 expression in human and mouse p53-deficient OS. Myc was aberrantly upregulated by Runx3 via mR1, a consensus Runx site in the Myc promoter, in a manner dependent on p53 deficiency. Reduction of the Myc level by disruption of mR1 or Runx3 knockdown decreased the tumorigenicity of p53-deficient OS cells and effectively suppressed OS development in OS mice. Furthermore, Runx inhibitors exerted therapeutic effects on OS mice. Together, these results show that p53 deficiency promotes osteosarcomagenesis in human and mouse by allowing Runx3 to induce oncogenic Myc expression.

category: cancer biology


title: Occurrence, functionality, and abundance of the TERT promoter mutations

abstract: Telomere shortening at chromosomal ends due to the constraints of the DNA replication process acts as a tumor suppressor by restricting the replicative potential in primary cells. Cancers evade that limitation primarily through the reactivation of telomerase via different mechanisms. Mutations within the promoter of the telomerase reverse transcriptase (TERT) gene represent a definite mechanism for the ribonucleic enzyme regeneration predominantly in cancers that arise from tissues with low rates of self-renewal. The promoter mutations cause a moderate increase in TERT transcription and consequent telomerase upregulation to the levels sufficient to delay replicative senescence but not prevent bulk telomere shortening and genomic instability. Since the discovery, a staggering number of studies and publications have resolved the discrete aspects, effects, and clinical relevance of the TERT promoter mutations. The promoter mutations link transcription of TERT with oncogenic pathways, associate with markers of poor outcome, and define patients with reduced survivals in several cancers. In this review, we discuss the occurrence and impact of the promoter mutations and highlight the mechanism of TERT activation. We further deliberate on the foundational question of the abundance of the TERT promoter mutations and a general dearth of functional mutations within noncoding sequences, as evident from pan-cancer analysis of the whole-genomes. We posit that the favorable genomic constellation within the TERT promoter may be less than a common occurrence in other noncoding functional elements. The evolutionary constraints limit the functional fraction within the human genome, hence the lack of abundant mutations outside the coding sequences.


title: A DUF1068 protein acts as a pectin biosynthesis scaffold and maintains Golgi morphology and cell adhesion in Arabidopsis.

abstract: Adjacent plant cells are connected by specialized cell wall regions, called middle lamellae, which influence critical agricultural characteristics, including fruit ripening and organ abscission. Middle lamellae are enriched in pectin polysaccharides, specifically homogalacturonan (HG). Here, we identify a plant-specific Arabidopsis DUF1068 protein, called NKS1, that is required for middle lamellae integrity and cell adhesion. NKS1 localises to the Golgi apparatus and loss of the protein results in changes to Golgi structure and function. The nks1 mutants also display HG deficient phenotypes, including reduced seedling growth, changes to cell wall composition, and tissue integrity defects. These phenotypes are identical to those of the HG deficient mutants qua1 and qua2. Notably, NKS1 physically interacts with both QUA1 and QUA2, and genetic interaction analyses reveal that they work in the same pathway. Based on these results we propose that NKS1 works as a scaffold for HG synthesis and that such scaffolding is important to support Golgi function and the organization of the pectin synthesis machinery.


title: DELAY OF GERMINATION 6, encoding the ANAC060 transcription factor, inhibits seed dormancy

abstract:
The timing of seed germination is regulated by seed dormancy. There is ample natural variation for seed dormancy among as well as within plant species. In Arabidopsis several DELAY OF GERMINATION quantitative trait loci have been identified, of which DOG1 is best studied. Here we report the identification of DOG6, a quantitative trait locus with a similar strong effect on seed dormancy as DOG1. DOG6 affects the timing of germination both in laboratory as well as in field conditions. Complementation cloning revealed that DOG6 encodes the membrane bound transcription factor ANAC060. The absence of the ANAC060 protein or its sequestration outside the nucleus results in increased seed dormancy levels. The different natural variants of ANAC060 differ for the presence of the membrane binding domain, either due to the fact that this domain is absent in the genomic sequence or because the cDNA is alternatively spliced. Our data indicates that ANAC060 regulates seed dormancy by among others binding to and regulating the expression of protein phosphatases 2C class A proteins including PROTEIN PHOSPHATASE 2CA (PP2CA), ABI FIVE BINDING PROTEIN 3 (AFP3) and HIGHLY ABA-INDUCED PP2C GENE 3 (HAI3).

Significance StatementANAC transcription factors are known to effect plant development as well as the response of plants to their environment. Here, we present the identification of DELAY OF GERMINATION 6 (DOG6), a seed dormancy quantitative trait locus that encodes the ANAC060 transcription factor. We have identified different natural alleles of ANAC060 and show that these genetic variants determine the localization of the protein. ANAC060 alleles that lack the membrane binding domain end up in the nucleus. Hence they affect transcription and as such attenuate seed dormancy.


title: Computational specialization within the cortical eye movement system

abstract: Animals actively sample their environment through actions such as whisking, sniffing, and saccadic eye movements. Computationally, sensorimotor control may be viewed as an interplay between two processes that place different demands on their neural circuits: a rapid/competitive process for promptly selecting each upcoming action, and a slow/integrative process weighing the outcomes of multiple prior actions to build a model of the environment. Using saccadic eye movements as a model system, we addressed the hypothesis that frontal and parietal cortex are computationally specialized for these two functions. Through biophysical modelling, we predicted neural signatures of the competitive and integrative processes. We localized these signals to the frontal eye fields and intra-parietal cortex, respectively, using whole-brain, high-temporal-resolution neuroimaging (MEG). This frontal/parietal specialization can be linked to the differential characteristics of cortical circuits, and thus may represent a more general organizing principle of sensorimotor function in the primate brain.


title: Use of Induced Pluripotent Stem Cells to Build Isogenic Systems and Investigate Type 1 Diabetes

abstract: Type 1 diabetes is a disease that arises due to complex immunogenetic mechanisms. Key cell-cell interactions involved in the pathogenesis of T1D are activation of autoreactive T cells by dendritic cells (DC), migration of T cells across endothelial cells (EC) lining capillary walls into the islets of Langerhans, interaction of T cells with macrophages in the islets, and killing of {beta}-cells by autoreactive CD8+ T cells. Overall, pathogenic cell-cell interactions are likely regulated by the individuals collection of genetic T1D-risk variants. To accurately model the role of genetics, it is essential to build systems to interrogate single candidate genes in isolation during the interactions of cells that are essential for disease development. However, obtaining single-donor matched cells relevant to T1D is a challenge. Sourcing these genetic variants from human induced pluripotent stem cells (iPSC) avoids this limitation. Herein, we have differentiated iPSC from one donor into DC, macrophages, EC, and {beta}-cells. Additionally, we also engineered T cell avatars from the same donor to provide an in vitro platform to study genetic influences on these critical cellular interactions. This proof of concept demonstrates the ability to derive an isogenic system from a single donor to study these relevant cell-cell interactions. Our system constitutes an interdisciplinary approach with a controlled environment that provides a proof-of-concept for future studies to determine the role of disease alleles (e.g. IFIH1, PTPN22, SH2B3, TYK2) in regulating cell-cell interactions and cell-specific contributions to the pathogenesis of T1D.

category: immunology


title: Soils and sediments host novel archaea with divergent monooxygenases implicated in ammonia oxidation

abstract: Copper membrane monooxygenases (CuMMOs) play critical roles in the global carbon and nitrogen cycles. Organisms harboring these enzymes perform the first, and rate limiting, step in aerobic oxidation of ammonia, methane, or other simple hydrocarbons. Within archaea, only organisms in the order Nitrososphaerales (Thaumarchaeota) encode CuMMOs, which function exclusively as ammonia monooxygenases. From grassland and hillslope soils and aquifer sediments, we identified 20 genomes from distinct archaeal species encoding divergent CuMMO sequences. These archaea are phylogenetically clustered in a previously unnamed Thermoplasmatota order, herein named the Ca. Angelarcheales. The CuMMO proteins in Ca. Angelarcheales are more similar in structure to those in ammonia-oxidizing archaea than those of bacteria, and they contain all functional residues required for activity. Similarly to the Nitrososphaerales, Ca. Angelarcheales genomes are significantly enriched in blue copper proteins (BCPs) relative to sibling lineages, including plastocyanin-like electron carriers and divergent nitrite reductase-like (nirK) 2-domain cupredoxin proteins co-located with electron transport machinery. Angelarcheales do not have identifiable genes for methanol oxidation or carbon fixation, encode significant capacity for peptide/amino acid uptake and degradation, and share numerous electron transport mechanisms with the Nitrososphaerales. In the studied soils and sediments Ca. Angelarcheales were at least as abundant as ammonia-oxidizing Nitrososphaerales. Thus, we predict that Angelarcheales live a mixotrophic lifestyle based on oxidation of ammonia liberated from peptide and amino acid degradation. This work expands the known diversity of Thermoplasmatota and of CuMMO enzymes in archaea and suggests that these organisms are important and previously unaccounted for contributors to nitrogen cycling.


title: Density-dependent effects are the main determinants of variation in growth dynamics between closely related bacterial strains

abstract:
Although closely related genetically, bacterial strains belonging to the same species show significant variability in their growth and death dynamics. However, our understanding of the underlying processes that lead to this variability is still lacking. Here, we measured the growth and death dynamics of 11 strains of E. coli originating from different hosts and developed a mathematical model that captures their growth and death dynamics. Our model considers two environmental factors that determine growth dynamics: resource utilization efficiency and density-dependent growth inhibition. Here we show that both factors are required to capture the measured dynamics. Interestingly, our model results indicate that the main process that determines the major differences between the strains is the critical density at which they slow down their growth, rather than maximal growth rate or death rate. Finally, we found that bacterial growth and death dynamics can be reduced to only two dimensions and described by death rates and density-dependent growth inhibition alone.

ImportanceUnderstanding the dynamics of bacterial growth has been an area of intense study. However, these dynamics have often been characterized through the narrow prism of describing growth rates, without considering parameters that may modulate these rates. Here, we generate a model that describes bacterial growth and death dynamics, incorporating two essential, growth-modulating factors: density-dependent reductions in growth rates and resource utilization efficiency. This model allows us to demonstrate that variation in the growth curves of closely related bacterial strains can be reduced to two dimensions and explained almost entirely by variation in the cellular density at which bacteria slow down their growth, combined with their death rates.


title: A conserved Guided Entry of Tail-anchored pathway is involved in the trafficking of tail-anchored membrane proteins in Plasmodium falciparum.

abstract:
Tail-anchored (TA) proteins are defined by the absence of N-terminus signal sequence and the presence of a single transmembrane domain (TMD) proximal to their extreme C-terminus. They play fundamental roles in cellular processes including vesicular trafficking, protein translocation and quality control. Accordingly, TA proteins are post-translationally integrated by the Guided Entry of TA (GET) pathway to the cellular membranes; with their N-terminus oriented towards the cytosol and C-terminus facing the organellar lumen. The TA repertoire and the GET machinery have been extensively characterized in the yeast and mammalian systems, however, they remain elusive in the human malaria parasite Plasmodium falciparum. In this study, we bioinformatically predicted a total of 63 TA proteins in the P. falciparum proteome and revealed the association of their subset with the P. falciparum homolog of Get3 (PfGet3). In addition, our proximity labelling studies either definitively identified or shortlisted the other eligible GET constituents, and our in vitro association studies validated associations between PfGet3 and the corresponding homologs of Get4 and Get2 in P. falciparum. Collectively, this study reveals the presence of proteins with hallmark TA signatures and the involvement of evolutionary conserved GET trafficking pathway for their targeted delivery within the parasite.

SynopsisTail-anchored (TA) proteins, characterized by an absence of N-terminal signal sequence and the presence of a transmembrane domain near the C-terminus, are post-translationally inserted at organellar membranes by the conserved multi-component Guided Entry of TA (GET) pathway. Here, we identified the putative homologs of GET machinery in the human malaria parasite Plasmodium falciparum and revealed their association with a subset of bioinformatically predicted 63 putative TA proteins, thereby validating the functional existence of this trafficking pathway within the apicomplexan parasite.

Graphical Abstract

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title: A genome-wide knock-out screen for actors of epigenetic silencing reveals new regulators of germline genes and 2-cell like cell state

abstract: Epigenetic mechanisms are essential to establish and safeguard cellular identities in mammals. They dynamically regulate the expression of genes, transposable elements, and higher-order chromatin structures. Expectedly, these chromatin marks are indispensable for mammalian development and alterations often lead to diseases such as cancer. Molecularly, epigenetic mechanisms rely on factors to establish patterns, interpret them into a transcriptional output, and maintain them across cell divisions. A global picture of these phenomena has started to emerge over the years, yet many of the molecular actors remain to be discovered. In this context, we have developed a reporter system sensitive to epigenetic perturbations to report on repressive pathways based on Dazl, which is normally repressed in mouse ES cells. We used this system for a genome-wide CRISPR knock-out screen, which yielded expected hits (DNMT1, UHRF1, MGA), as well as novel candidates. We prioritized the candidates by secondary screens, and led further experiments on 6 of them: ZBTB14, KDM5C, SPOP, MCM3AP, BEND3, and KMT2D. Our results show that all 6 candidates regulate the expression of germline genes. In addition, we find that removal of ZBTB14, KDM5C, SPOP and MCM3AP led to similar transcriptional responses, including a reactivation of the 2-cell like cell (2CLC) signature. Therefore, our genetic screen has identified new regulators of key cellular states.


title: Functional characterisation of banana (Musa spp.) 2-oxoglutarate-dependent dioxygenases involved in flavonoid biosynthesis

abstract:
Bananas (Musa) are non-grass, monocotyledonous, perennial plants that are well-known for their edible fruits. Their cultivation provides food security and employment opportunities in many countries. Banana fruits contain high levels of minerals and phytochemicals, including flavonoids, which are beneficial for human nutrition. To broaden the knowledge on flavonoid biosynthesis in this major crop plant, we aimed to identify and functionally characterise selected structural genes encoding 2-oxoglutarate-dependent dioxygenases, involved in the formation of the flavonoid aglycon.

Musa candidates genes predicted to encode flavanone 3-hydroxylase (F3H), flavonol synthase (FLS) and anthocyanidin synthase (ANS) were assayed. Enzymatic functionalities of the recombinant proteins were confirmed in vivo using bioconversion assays. Moreover, transgenic analyses in corresponding Arabidopsis thaliana mutants showed that MusaF3H, MusaFLS and MusaANS were able to complement the respective loss-of-function phenotypes, thus verifying functionality of the enzymes in planta.

Knowledge gained from this work provides a new aspect for further research towards genetic engineering of flavonoid biosynthesis in banana fruits to increase their antioxidant activity and nutritional value.


title: The ALOG family members OsG1L1 and OsG1L2 regulate inflorescence branching in rice

abstract:
The architecture of the rice inflorescence is an important determinant of seed yield. The length of the inflorescence and the number of branches are among the key factors determining the amount of spikelets, and thus seeds, that will develop. Especially the timing of the identity transition from indeterminate branch meristem to determinate spikelet meristem regulates the complexity of the inflorescence. In this context, the ALOG gene TAWAWA1 (TAW1) has been shown to delay the transition to determinate spikelet development in rice. Recently, by combining precise laser microdissection of inflorescence meristems with RNA-seq we observed that two ALOG genes, Oryza sativa OsG1-like 1 (OsG1L1) and OsG1L2, have an expression profile similar to TAW1. Here we report that osg1l1 and osg1l2 loss-of-function CRISPR mutants have similar phenotypes as the taw1 mutant, suggesting that these genes might act on related pathways during inflorescence development. Transcriptome analysis of the osg1l2 mutant suggested interactions of OsG1L2 with other known inflorescence architecture regulators and the datasets were also used for the construction of a gene regulatory network (GRN) proposing interactions between genes potentially involved in controlling inflorescence development in rice.

The spatio-temporal expression profiling and phenotypical analysis of CRISPR loss-of-function mutants of the homeodomain-leucine zipper transcription factor gene OsHOX14 suggest that the proposed GRN indeed serves as a valuable resource for the identification of new players involved in rice inflorescence development.

One-sentence summaryOsG1L1 and OsG1L2 control panicle architecture through delaying the transition from indeterminate branch- to determinate spikelet-meristem identity.

category: developmental biology


title: Orthology clusters from gene trees with Possvm

abstract: Possvm (Phylogenetic Ortholog Sorting with Species oVerlap and MCL) is a tool that automates the process of classifying clusters of orthologous genes from precomputed phylogenetic trees. It identifies orthology relationships between genes using the species overlap algorithm to infer taxonomic information from the gene tree topology, and then uses the Markov Clustering Algorithm (MCL) to identify orthology clusters and provide annotated gene family classifications. Our benchmarking shows that this approach, when provided with accurate phylogenies, is able to identify manually curated orthogroups with high precision and recall. Overall, Possvm automates the routine process of gene tree inspection and annotation in a highly interpretable manner, and provides reusable outputs that can be used to obtain phylogeny-informed gene annotations and inform comparative genomics and gene family evolution analyses.

category: evolutionary biology


title: Marginal cost of contextualizing stigma of zoonotic diseases

abstract:
BackgroundIn the medical sphere, understanding naming conventions strengthen the integrity of naming human diseases remains nominal rather than substantial yet. Since the current nosology-based standard for human diseases could not offer a one-size-fits-all corrective mechanism, many idiomatic but flawed names frequently appear in scientific literature and news outlets at the cost of sociocultural impacts.

ObjectiveWe attempt to examine the ethical oversights of current naming practices and propose heuristic rationales and approaches to determine a pithy name instead of an inopportune nosology.

MethodsFirst, we examined the compiled global online news volumes and emotional tones on some inopportune nosology like German measles, Middle Eastern Respiratory Syndrome, Spanish flu, Hong Kong flu, and Huntingtons disease in the wake of COVID-19. Second, we prototypically scrutinize the lexical dynamics and pathological differentials of German measles and common synonyms by leveraging the capacity of the Google Books Ngram Corpus. Third, we demonstrated the empirical approaches to curate an exclusive substitute for an anachronistic nosology German measles based on deep learning models and post-hoc explanations.

ResultsThe infodemiological study shows that the public informed the offensive names with extremely negative tones in textual and visual narratives. The findings of the historiographical study indicate that many synonyms of German measles did not survive, while German measles became an anachronistic usage, and rubella has taken the dominant place since 1994. The PubMedBERT model could identify rubella as a potential substitution for German measles with the highest semantic similarity. The results of the semantic drift experiments further indicate that rubella tends to survive during the ebb and flow of semantic drift.

ConclusionsOur findings indicate that the nosological evolution of anachronistic names could result in sociocultural impacts without a corrective mechanism. To mitigate such impacts, we introduce some ethical principles for formulating an improved naming scheme. Based on deep learning models and post-hoc explanations, our illustrated experiments could provide hallmark references to the remedial mechanism of naming practices and pertinent credit allocations.

category: scientific communication and education


title: Naming of human diseases on the wrong side of history


title: Naming Human Diseases: Ethical Principles of Curating Exclusive Substitute for Inopportune Nosology


title: Agrochemical control of gene expression using evolved split RNA polymerase

abstract: Chemical inducible gene expression systems are valuable tools for rational control of gene expression both for basic research and biotechnology. However, most chemical inducers are confined to certain groups of organisms. Therefore, dissecting interaction between different organisms could be challenging using existing chemical inducible systems. We engineered a mandipropamid induced gene expression system (Mandi-T7) based on evolved split T7 RNAP system. As a proof-of-principle, we induced GFP expression in E. coli cells grown inside plant tissue.

category: synthetic biology


title: Open issues for protein function assignment in Haloferax volcanii and other halophilic archaea

abstract:
BackgroundAnnotation ambiguities and annotation errors are a general challenge in genomics. While a reliable protein function assignment can be obtained by experimental characterization, this is expensive and time-consuming, and the number of such Gold Standard Proteins (GSP) with experimental support remains very low compared to proteins annotated by sequence homology, usually through automated pipelines. Even a GSP may give a misleading assignment when used as a reference: the homolog may be close enough to support isofunctionality, but the substrate of the GSP is absent from the species being annotated. In such cases the enzymes cannot be isofunctional. Here, we examine a variety of such issues in halophilic archaea (class Halobacteria), with a strong focus on the model haloarchaeon Haloferax volcanii.

ResultsAnnotated proteins of Hfx. volcanii were identified for which public databases tend to assign a function that is probably incorrect. In some cases, an alternative, probably correct, function can be predicted or inferred from the available evidence but this has not been adopted by public databases because experimental validation is lacking. In other cases, a probably invalid specific function is predicted by homology, and while there is evidence that this assigned function is unlikely, the true function remains elusive. We list 50 of those cases, each with detailed background information so that a conclusion about the most likely biological function can be drawn. For reasons of brevity and comprehension, only key aspects are listed in the main text, with detailed information being provided in a corresponding section of the Supplementary Material.

ConclusionsCompiling, describing and summarizing these open annotation issues and functional predictions will benefit the scientific community in the general effort to improve the evaluation of protein function assignments and more thoroughly detail them. By highlighting the gaps and likely annotation errors currently in the databases, we hope this study will provide a framework for experimentalists to systematically confirm (or disprove) our function predictions or to uncover yet unexpected functions.


title: SARS-CoV-2 spike protein induces brain pericyte immunoreactivity in absence of productive viral infection

abstract: COVID-19 is a respiratory disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). COVID-19 pathogenesis causes vascular-mediated neurological disorders via still elusive mechanisms. SARS-CoV-2 infects host cells by binding to angiotensin-converting enzyme 2 (ACE2), a transmembrane receptor that recognizes the viral spike (S) protein. Brain pericytes were recently shown to express ACE2 at the neurovascular interface, outlining their possible implication in microvasculature injury in COVID-19. Yet, pericyte responses to SARS-CoV-2 is still to be fully elucidated. Using cell-based assays, we report that ACE2 expression in human brain vascular pericytes is highly dynamic and is increased upon S protein stimulation. Pericytes exposed to S protein underwent profound phenotypic changes translated by increased expression of contractile and myofibrogenic proteins, namely -smooth muscle actin (-SMA), fibronectin, collagen I, and neurogenic locus notch homolog protein-3 (NOTCH3). These changes were associated to an altered intracellular calcium (Ca2+) dynamic. Furthermore, S protein induced lipid peroxidation, oxidative and nitrosative stress in pericytes as well as triggered an immune reaction translated by activation of nuclear factor-kappa-B (NF-{kappa}B) signalling pathway, which was potentiated by hypoxia, a condition associated to vascular comorbidities, which exacerbate COVID-19 pathogenesis. S protein exposure combined to hypoxia enhanced the production of pro-inflammatory cytokines involved in immune cell activation and trafficking, namely interleukin-8 (IL-8), IL-18, macrophage migration inhibitory factor (MIF), and stromal cell-derived factor-1 (SDF-1). Finally, we found that S protein could reach the mouse brain via the intranasal route and that reactive ACE2-expressing pericytes are recruited to the damaged tissue undergoing fibrotic scarring in a mouse model of cerebral multifocal micro-occlusions, a main reported vascular-mediated neurological condition associated to COVID-19. Our data demonstrate that the released S protein is sufficient to mediate pericyte immunoreactivity, which may contribute to microvasculature injury in absence of a productive viral infection. Our study provides a better understanding for the possible mechanisms underlying cerebrovascular disorders in COVID-19, paving the way to develop new therapeutic interventions.


title: Inhibiting LSD1 suppresses coronavirus-induced inflammation but spares innate antiviral activity

abstract:
Tissue-resident macrophages exert critical but conflicting effects on the progression of coronavirus infections by secreting both anti-viral type I Interferons and tissue-damaging inflammatory cytokines. Steroids, the only class of host-targeting drugs approved for Covid19, indiscriminately suppress both responses, possibly impairing viral clearance, and provide limited clinical benefit. Here we set up a mouse in vitro co-culture system that reproduces the macrophage response to SARS-CoV2 seen in patients and allows quantitation of inflammatory and antiviral activities. We show that the NFKB-dependent inflammatory response can be selectively inhibited by ablating the lysine-demethylase LSD1, which additionally unleashed interferon-independent ISG activation and blocked viral egress through the lysosomal pathway. These results provide a rationale for repurposing LSD1 inhibitors, a class of drugs extensively studied in oncology, for Covid-19 treatment.

One-Sentence SummaryTargeting a chromatin-modifying enzyme in coronavirus infections curbs tissue-damage without affecting antiviral response


title: SARS -CoV-2 T-cell immunity to variants of concern following vaccination

abstract: Recently, two mRNA vaccines to severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) have become available, but there is also an emergence of SARS-CoV-2 variants with increased transmissibility and virulence1-6. A major concern is whether the available vaccines will be equally effective against these variants. The vaccines are designed to induce an immune response against the SARS-CoV-2 spike protein7, 8, which is required for viral entry to host cells9. Immunity to SARS-CoV-2 is often evaluated by antibody production, while less is known about the T-cell response. Here we developed, characterized, and implemented two standardized, functional assays to measure T-cell immunity to SARS-CoV-2 in uninfected, convalescent, and vaccinated individuals. We found that vaccinated individuals had robust T-cell responses to the wild type spike and nucleocapsid proteins, even more so than convalescent patients. We also found detectable but diminished T-cell responses to spike variants (B.1.1.7, B.1.351, and B.1.1.248) among vaccinated but otherwise healthy donors. Since decreases in antibody neutralization have also been observed with some variants10-12, investigation into the T-cell response to these variants as an alternative means of viral control is imperative. Standardized measurements of T-cell responses to SARS-CoV-2 are feasible and can be easily adjusted to determine changes in response to variants.


title: Preliminary Immunogenicity of a Pan-COVID-19 T Cell Vaccine in HLA-A*02:01 Mice

abstract: New strains of SARS-CoV-2 have emerged, including B.1.351 and P.1, that demonstrate increased transmissibility and the potential of rendering current SARS-CoV-2 vaccines less effective. A concern is that existing SARS-CoV-2 spike subunit vaccines produce neutralizing antibodies to three dimensional spike epitopes that are subject to change during viral drift. Here we provide an initial report on the hypothesis that adaptive T cell based immunity may provide a path for a pan-COVID-19 vaccine that is resilient to viral drift. T cell based adaptive immunity can be based on short peptide sequences selected from the viral proteome that are less subject to drift, and can utilize multiple such epitopes to provide redundancy in the event of drift. We find that SARS-CoV-2 peptides contained in a mRNA-LNP T cell vaccine for SARS-CoV-2 are immunogenic in mice transgenic for the human HLA-A*02:01 gene. We plan to test the efficacy of this vaccine with SARS-CoV-2 B.1.351 challenge trials with HLA-A*02:01 mice.


title: Convergent antibody responses to the SARS-CoV-2 spike protein in convalescent and vaccinated individuals

abstract: Unrelated individuals can produce genetically similar clones of antibodies, known as public clonotypes, which have been seen in responses to different infectious diseases as well as healthy individuals. Here we identify 37 public clonotypes in memory B cells from convalescent survivors of SARS-CoV-2 infection or in plasmablasts from an individual after vaccination with mRNA-encoded spike protein. We identified 29 public clonotypes, including clones recognizing the receptor-binding domain (RBD) in the spike protein S1 subunit (including a neutralizing, ACE2-blocking clone that protects in vivo), and others recognizing non-RBD epitopes that bound the heptad repeat 1 region of the S2 domain. Germline-revertant forms of some public clonotypes bound efficiently to spike protein, suggesting these common germline-encoded antibodies are preconfigured for avid recognition. Identification of large numbers of public clonotypes provides insight into the molecular basis of efficacy of SARS-CoV-2 vaccines and sheds light on the immune pressures driving the selection of common viral escape mutants.


title: Signaling through FcγRIIA and the C5a-C5aR pathway mediates platelet hyperactivation in COVID-19

abstract:
Patients with COVID-19 present with a wide variety of clinical manifestations. Thromboembolic events constitute a significant cause of morbidity and mortality in patients infected with SARS-CoV-2. Severe COVID-19 has been associated with hyperinflammation and pre-existing cardiovascular disease. Platelets are important mediators and sensors of inflammation and are directly affected by cardiovascular stressors. In this report, we found that platelets from severely ill, hospitalized COVID-19 patients exhibit higher basal levels of activation measured by P-selectin surface expression, and have a poor functional reserve upon in vitro stimulation. Correlating clinical features to the ability of plasma from COVID-19 patients to stimulate control platelets identified ferritin as a pivotal clinical marker associated with platelet hyperactivation. The COVID-19 plasma-mediated effect on control platelets was highest for patients that subsequently developed inpatient thrombotic events. Proteomic analysis of plasma from COVID-19 patients identified key mediators of inflammation and cardiovascular disease that positively correlated with in vitro platelet activation. Mechanistically, blocking the signaling of the Fc{gamma}RIIa-Syk and C5a-C5aR pathways on platelets, using antibody-mediated neutralization, IgG depletion or the Syk inhibitor fostamatinib, reversed this hyperactivity driven by COVID-19 plasma and prevented platelet aggregation in endothelial microfluidic chamber conditions, thus identifying these potentially actionable pathways as central for platelet activation and/or vascular complications in COVID-19 patients. In conclusion, we reveal a key role of platelet-mediated immunothrombosis in COVID-19 and identify distinct, clinically relevant, targetable signaling pathways that mediate this effect. These studies have implications for the role of platelet hyperactivation in complications associated with SARS-CoV-2 infection.

Cover illustration O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

One-sentence summaryThe Fc{gamma}RIIA and C5a-C5aR pathways mediate platelet hyperactivation in COVID-19


title: Human organoid systems reveal in vitro correlates of fitness for SARS-CoV-2 B.1.1.7

abstract:
A new phase of the COVID-19 pandemic has started as several SARS-CoV-2 variants are rapidly emerging globally, raising concerns for increased transmissibility. As animal models and traditional in vitro systems may fail to model key aspects of the SARS-CoV-2 replication cycle, representative in vitro systems to assess variants phenotypically are urgently needed. We found that the British variant (clade B.1.1.7), compared to an ancestral SARS-CoV-2 clade B virus, produced higher levels of infectious virus late in infection and had a higher replicative fitness in human airway, alveolar and intestinal organoid models. Our findings unveil human organoids as powerful tools to phenotype viral variants and suggest extended shedding as a correlate of fitness for SARS-CoV-2.

One-Sentence SummaryBritish SARS-CoV-2 variant (clade B.1.1.7) infects organoids for extended time and has a higher fitness in vitro.


title: SARS-CoV-2 Genome Sequencing Methods Differ In Their Ability To Detect Variants From Low Viral Load Samples

abstract: SARS-CoV-2 genomic surveillance has been vital in understanding the spread of COVID-19, the emergence of viral escape mutants and variants of concern. However, low viral loads in clinical specimens affect variant calling for phylogenetic analyses and detection of low frequency variants, important in uncovering infection transmission chains. We systematically evaluated three widely adopted SARS-CoV-2 whole genome sequencing methods for their sensitivity, specificity, and ability to reliably detect low frequency variants. Our analyses highlight that the ARTIC v3 protocol consistently displays high sensitivity for generating complete genomes at low viral loads compared with the probe-based Illumina respiratory viral oligo panel, and a pooled long-amplicon method. We show substantial variability in the number and location of low-frequency variants detected using the three methods, highlighting the importance of selecting appropriate methods to obtain high quality sequence data from low viral load samples for public health and genomic surveillance purposes.