title: Expansive Linguistic Representations to Predict Interpretable Odor Mixture Discriminability

abstract: Language is often thought as being poorly adapted to precisely describe or quantify smell and olfactory attributes. In this work, we show that semantic descriptors of odors can be implemented in a model to successfully predict odor mixture discriminability, an olfactory attribute. We achieved this by taking advantage of the structure-to-percept model we previously developed for monomolecular odorants, using chemical descriptors to predict pleasantness, intensity and 19 semantic descriptors such as  fish,  cold,  burnt,  garlic,  grass and  sweet for odor mixtures, followed by a metric learning to obtain odor mixture discriminability. Through this expansion of the representation of olfactory mixtures, our Semantic model outperforms state of the art methods by taking advantage of the intermediary semantic representations learned from human perception data to enhance and generalize the odor discriminability/similarity predictions. As 10 of the semantic descriptors were selected to predict discriminability/similarity, our approach meets the need of rapidly obtaining interpretable attributes of odor mixtures as illustrated by the difficulty of finding olfactory metamers. More fundamentally, it also shows that language can be used to establish a metric of discriminability in the everyday olfactory space.


title: A Neurodynamic Model of Inter-Brain Coupling in the Gamma Band

abstract: The use of EEG to simultaneously record multiple brains (i.e., hyperscanning) during social interactions has led to the discovery of inter-brain coupling (IBC). IBC is defined as the neural synchronization between people and is considered to be a marker of social interaction. IBC has previously been observed across different frequency bands, including Theta [4-7 Hz]. Given the proximity of this frequency range with behavioral rhythms, models have been able to combine IBC in Theta with sensorimotor coordination patterns. Interestingly, empirical EEG-hyperscanning results also report the emergence of IBC in the Gamma range [>30 Hz]. Gamma oscillations fast and transient nature makes a direct link between Gamma-IBC and other (much slower) interpersonal dynamics difficult, leaving Gamma-IBC without a plausible model. However, at the intra-brain level, Gamma activity is coupled with the dynamics of lower frequencies through cross-frequency coupling (CFC). This paper provides a biophysical explanation for the emergence of Gamma inter-brain coupling using a Kuramoto model of four oscillators divided into two separate (brain) units. By modulating both the degree of inter-brain coupling in the Theta band (i.e., between-units coupling) and CFC (i.e., intra-unit Theta-Gamma coupling), we provide a theoretical explanation of the observed Gamma-IBC phenomenon in the EEG-hyperscanning literature.

category: neuroscience


title: Neural mass modelling for the masses: Democratising access to whole-brain biophysical modelling with FastDMF

abstract:
Different whole-brain models constrained by neuroimaging data have been developed during the last years to investigate causal hypotheses related to brain mechanisms. Among these, the Dynamic Mean Field (DMF) model is a particularly attractive model, combining a biophysically realistic single-neuron model that is scaled up via a mean-field approach and multimodal imaging data. Despite these favourable features, an important barrier for a widespread usage of the DMF model is that current implementations are computationally expensive - to the extent that the model often becomes unfeasible when no high-performance computing infrastructure is available. Furthermore, even when such computing structure is available, current implementations can only support simulations on brain parcellations that consider less than 100 brain regions. To remove these barriers, here we introduce a user-friendly and computationally-efficient implementation of the DMF model, which we call FastDMF, with the goal of making biophysical whole-brain modelling accessible to neuroscientists worldwide. By leveraging a suit of analytical and numerical advances - including a novel estimation of the feedback inhibition control parameter, and a Bayesian optimisation algorithm - the FastDMF circumvents various computational bottlenecks of previous implementations. An evaluation of the performance of the FastDMF showed that it can attain a significantly faster performance than previous implementations while reducing the memory consumption by several orders of magnitude. Thanks to these computational advances, FastDMF makes it possible to increase the number of simulated regions by one order of magnitude: we found good agreement between empirical and simulated functional MRI data parcellated at two different spatial scales (N=90 and N=1000 brain regions). These advances open the way to the widespread use of biophysically grounded whole-brain models for understanding the interplay among anatomy, function and brain dynamics in health and disease, and to provide mechanistic explanations of recent results obtained from empirical fine-grained neuroimaging data sets, such as turbulence or connectome harmonics.

HighlightsO_LIWe present the FastDMF, a user-friendly and computationally efficient implementation of the Dynamic Mean Field model for simulations of whole-brain dynamics.
C_LIO_LIUsing analytical and numerical tools, we develop a novel estimation of the feedback inhibition control based on the structural connectivity, bypassing an important computational bottleneck.
C_LIO_LIThe FastDMF is coupled with a Bayesian Optimization algorithm significantly reducing the number of simulations required to fit the FastDMF to empirical neuroimaging data.
C_LIO_LIOur advances open the possibility of simulating thousands of brain regions in a biophysically grounded whole-brain model.
C_LI


title: Neuronal activity regulates Matrin 3 levels and function in a calcium-dependent manner through calpain cleavage and calmodulin binding

abstract: RNA-binding protein (RBP) dysfunction is a fundamental hallmark of amyotrophic lateral sclerosis (ALS) and related neuromuscular disorders. Abnormal neuronal excitability is also a conserved feature in ALS patients and disease models, yet little is known about how activity-dependent processes regulate RBP levels and functions. Mutations in the gene encoding the RBP Matrin 3 (MATR3) cause familial disease, and MATR3 pathology has also been observed in sporadic ALS, suggesting a key role for MATR3 in disease pathogenesis. Here, we show that glutamatergic activity drives MATR3 degradation in a NMDAR-, Ca2+-, and calpain-dependent mechanism. The most common pathogenic MATR3 mutation renders it resistant to calpain degradation, suggesting a link between activity-dependent MATR3 regulation and disease. We also demonstrate that Ca2+ regulates MATR3 through a non-degradative process involving the binding of Ca2+/calmodulin (CaM) to MATR3 and inhibition of its RNA-binding ability. These findings indicate that neuronal activity impacts both the abundance and function of MATR3, and provide a foundation for further study of Ca2+-coupled regulation of RBPs implicated in ALS and related neurological diseases.


title: Every individual makes a difference: A trinity derived from linking individual brain morphometry, connectivity and mentalising ability

abstract:
Mentalising ability, indexed as the ability to understand others beliefs, feelings, intentions, thoughts, and traits, is a pivotal and fundamental component of human social cognition. How-ever, considering the multifaceted nature of mentalising ability, little research has focused on characterising individual differences in different mentalising components. And even less research has been devoted to investigating how the variance in the structural and functional patterns of the amygdala and hippocampus, two vital subcortical regions of the  social brain, are related to inter-individual variability in mentalising ability. Here, as a first step toward filling these gaps, we exploited inter-subject representational similarity analysis (IS-RSA) to assess relationships between amygdala and hippocampal morphometry (surface-based multivariate morphometry statistics, MMS), connectivity (resting-state functional connectivity, rs-FC) and mentalising ability (interactive mentalisation questionnaire (IMQ) scores) across the participants (N = 24). In IS-RSA, we proposed a novel pipeline, i.e., computing patching and pooling operations-based surface distance (CPP-SD), to obtain a decent representation for high-dimensional MMS data. On this basis, we found significant correlations (i.e., secondorder isomorphisms) between these three distinct modalities, indicating that a trinity existed in idiosyncratic patterns of brain morphometry, connectivity and mentalising ability. Notably, a region-related mentalising specificity emerged from these associations: self-self and self-other mentalisation are more related to the hippocampus, while other-self mentalisation shows a closer link with the amygdala. Furthermore, by utilising the dyadic regression analysis, we observed significant interactions such that subject pairs with similar morphometry had even greater mentalising similarity if they were also similar in rs-FC. Altogether, we demonstrated the feasibility and illustrated the promise in using IS-RSA to study individual differences, deepening our understanding of how individual brains give rise to their mentalising abilities.

O_QD But this general character is contained in every individual character; without individual character there can be no general character. If all individual character were removed, what general character would remain?

C_QD

(MO_SCPLOWAOC_SCPLOW TO_SCPLOWSEC_SCPLOWO_SCPCAP-C_SCPCAPO_SCPLOWTUNGC_SCPLOW - OO_SCPLOWNC_SCPLOW CO_SCPLOWONTRADICTIONC_SCPLOW1)


title: Condensation of LINE-1 is required for retrotransposition

abstract: LINE-1 (L1) is the only autonomously active retrotransposon in the human genome, and accounts for 17% of the human genome. The L1 mRNA encodes two proteins, ORF1p and ORF2p. ORF1p is a homotrimeric RNA-binding protein that plays a critical role in assembling functional L1 ribonucleoprotein (RNP) complexes. Here we show that condensation of ORF1p is required for L1 retrotransposition. Using a combination of biochemical reconstitution and live-cell imaging, we demonstrate that RNA binding, electrostatic interactions, and trimer conformational dynamics together tune the properties of ORF1p assemblies to allow for efficient L1 condensate formation in cells. Furthermore, we directly relate the dynamics of ORF1p assembly to the ability to complete the entire retrotransposon life-cycle. Mutations that prevented ORF1 condensation led to loss of retrotransposition activity, while orthogonal restoration of coiled-coil conformational flexibility rescued both condensation and retrotransposition. Based on these observations, we propose that ORF1p oligomerization on L1 RNA drives the formation of a dynamic L1 condensate that is essential for retrotransposition.

category: cell biology


title: Positive fitness effects help explain the broad range of Wolbachia prevalences in natural populations

abstract: The bacterial endosymbiont Wolbachia is best known for its ability to modify its hosts reproduction by inducing cytoplasmic incompatibility (CI) to facilitate its own spread. Classical models predict either near-fixation of costly Wolbachia once the symbiont has overcome a threshold frequency (invasion barrier), or Wolbachia extinction if the barrier is not overcome. However, natural populations do not all follow this pattern: Wolbachia can also be found at low frequencies that appear stable over time. Wolbachia is known to have pleiotropic fitness effects (beyond CI) on its hosts. Existing models typically focus on the possibility that these are negative. Here we consider the possibility that the symbiont provides direct benefits to infected females (e.g. resistance to pathogens) in addition to CI. We discuss an underappreciated feature of Wolbachia dynamics: that CI with pleiotropy can produce low-frequency (<0.5) stable equilibria, when pleiotropy allows infected hosts to enjoy some fitness advantages. Additionally, without direct positive fitness effect, any stable equilibrium close to 0.5 will be sensitive to perturbations, which make such equilibria unlikely to sustain in nature. The results hold for both diplodiploid and different haplodiploid versions of CI. We suggest that insect populations showing low-frequency Wolbachia infection rates might host CI-inducing symbiotic strains providing additional (hidden or known) benefits to their hosts, especially when classical explanations (ongoing invasion, source-sink dynamics) have been ruled out.

category: ecology


title: Independent acquisition of short insertions at the RIR1 site in the spike N-terminal domain of the SARS-CoV-2 BA.2 lineage

abstract:
Although the SARS-CoV-2 variants BA.1 and BA.2 share over 30 non-synonymous substitutions in the spike glycoprotein, they show several unique mutations that were likely acquired after the split between these two major omicron lineages. One of the most intriguing mutations associated with BA.1 is the presence of the inserted tripeptide Glu-Pro-Glu within the N-terminal domain. While the functional implications of this insertion are still unclear, several other SARS-CoV-2 lineages had previously independently acquired similarly short insertions at the very same site, named RIR1. We have previously identified this site, located approximately between codon 212 and codon 216, as a hotspot of insertions, which usually involve small nucleotide sequences including three or four codons.

Here we show that similar insertion events have independently occurred at least 13 times in early 2022 within the BA.2 lineage, being occasionally associated with significant community transmission. One of these omicron sublineages, characterized by a Ser-Gly-Arg insertion in position 212, is responsible of over 2% of all SARS-CoV-2 cases recorded in Denmark, as of early April 2022. Molecular surveillance data highlight a slow but steady growth compared with the parental BA.2 lineage in all Danish regions, suggesting that the RIR1 insertion may confer a selective advantage. We report the identification of other currently circulating BA.2 sublineages showing similar insertions, whose spread should be therefore carefully monitored in the upcoming months.

category: genomics


title: Highly Parallelized, Multicolor Optogenetic Recordings of Cellular Activity for Therapeutic Discovery Applications in Ion Channels and Disease-associated Excitable Cells

abstract: Optogenetic assays provide a flexible, scalable and information rich approach to probe compound effects for ion channel drug targets in both heterologous expression systems and associated disease relevant cell types. Despite the potential utility and growing adoption of optogenetics, there remains a critical need for compatible platform technologies with the speed, sensitivity, and throughput to enable their application to broader drug screening applications. To address this challenge, we developed the Swarm, a custom designed optical instrument for highly parallelized, multicolor measurements in excitable cells, simultaneously recording changes in voltage and calcium activities at high temporal resolution under optical stimulation. The compact design featuring high power LEDs, large numerical aperture optics, and fast photodiode detection enables all-optical individual well readout of 24-wells simultaneously from multi-well plates while maintaining sufficient temporal resolution to probe millisecond response dynamics. The Swarm delivers variable intensity blue-light optogenetic stimulation to enable membrane depolarization and red or lime-light excitation to enable fluorescence detection of the resulting changes in membrane potential or calcium levels, respectively. The Swarm can screen ~10,000 wells / day in 384-well format, probing complex pharmacological interactions via a wide array of stimulation protocols. To evaluate the Swarm screening system, we optimized a series of heterologous optogenetic spiking HEK293 cell assays for several voltage-gated sodium channel subtypes including Nav1.2, Nav1.5, and Nav1.7. The Swarm was able to record pseudo-action potentials stably across all 24 objectives and provided pharmacological characterization of diverse sodium channel blockers. We performed a Nav1.7 screen of 200,000 small molecules in a 384-well plate format with all 560 plates reaching a Z[≥]0.5. As a demonstration of the versatility of the Swarm, we also developed an assay measuring cardiac action potential and calcium waveform properties simultaneously under paced conditions using human induced pluripotent stem (iPS) cell-derived cardiomyocytes as an additional counter screen for cardiac toxicity. In summary, the Swarm is a novel high-throughput all-optical system capable of collecting information-dense data from optogenetic assays in both heterologous and iPS cell-derived models, which can be leveraged to drive diverse therapeutic discovery programs for nervous system disorders and other disease areas involving excitable cells.

category: bioengineering


title: Subtyping of major SARS-CoV-2 variants reveals different transmission dynamics

abstract: SARS-CoV-2 continues to evolve, causing waves of the pandemic. Up to March 2022, eight million genome sequences have accumulated, which are classified into five major variants of concern. With the growing number of sequenced genomes, analysis of the big dataset has become increasingly challenging. Here we developed systematic approaches for comprehensive subtyping and pattern recognition for transmission dynamics. By analyzing the first two million viral genomes as of July 2021, we found that different subtypes of the same variant exhibited distinct temporal trajectories. For example, some Delta subtypes did not spread rapidly, while others did. We identified sets of characteristic single nucleotide variations (SNVs) that appeared to enhance transmission or decrease efficacy of antibodies for some subtypes of the Delta and Alpha variants. We also identified a set of SNVs that appeared to suppress transmission or increase viral sensitivity to antibodies. These findings are later confirmed in an analysis of six million genomes as of December 2021. For the Omicron variant, the dominant type in the world, we identified the subtypes with enhanced and suppressed transmission in an analysis of seven million genomes as of January 2022 and further confirmed the findings in a later analysis of eight million genomes as of March 2022. While the "enhancer" SNVs exhibited an enriched presence on the spike protein, the "suppressor" SNVs are mainly elsewhere. Disruption of the SNV correlation largely destroyed the enhancer-suppressor phenomena. These results suggest the importance of fine subtyping of variants, and point to potential complex interactions among SNVs.

category: bioinformatics


title: Candidate genes associated with neurological manifestations of COVID-19: Meta-analysis using multiple computational approaches

abstract: COVID-19 develops certain neurological symptoms, the molecular pathophysiology of which is obscure. In the present study, two networks were constructed and their hub-bottleneck and driver nodes were evaluated to consider them as  target genes followed by identifying  candidate genes and their associations with neurological phenotypes of COVID-19. A tripartite network was first constructed using literature-based neurological symptoms of COVID-19 as input. The target genes evaluated therefrom were then used as query genes to identify the co-expressed genes from the RNA-sequence data of the frontal cortex of COVID-19 patients using pair-wise mutual information to genes. A  combined gene network (CGN) was constructed with 189 genes selected from TN and 225 genes co-expressed in COVID-19. Total 44  target genes evaluated from both networks and their connecting genes in respective networks were analyzed functionally by measuring pair-wise  semantic similarity scores (SSS) and finding Enrichr annotation terms against a set of genes. A new integrated  weighted harmonic mean score was formulated using SSS and STRING-based  combined score to select 21 gene-pairs among  target genes that provided 21  candidate genes with their properties as  indispensable driver nodes of CGN. Finally, six pairs providing seven prevalent candidate genes (ADAM10, ADAM17, AKT1, CTNNB1, ESR1, PIK3CA, FGFR1) exhibited direct linkage with the neurological phenotypes under tumour/cancer, cellular signalling, neurodegeneration and neurodevelopmental diseases. The other phenotypes under behaviour/cognitive and motor dysfunctions showed indirect associations with the former genes through other candidate genes. The pathophysiology of  prevalent candidate genes has been discussed for better interpretation of neurological manifestation in COVID-19.

category: systems biology


title: Genotypic and phenotypic diversity of the multidrug-resistant Mycobacterium tuberculosis strains from eastern India

abstract: Mycobacterium tuberculosis (Mtb) poses a great challenge to human health and wellbeing and hinders economic growth of a region. India along with other south east Asian countries are known as high Tuberculosis burden countries. Adoption of whole genome sequencing in studying genetic diversity, evolution, transmission pattern and drug resistance development provided a great opportunity for developing and improving diagnostic and therapeutic approaches. In our study we have sequenced 118 Mtb whole genome from North East(NE) and Odisha as a representative of the diversity in eastern region of India for the first time. We observed high prevalence of multi-drug resistant(MDR) lineage-2(n=52) strains in NE whereas presence of mostly lineage-1(n=30) & 3 (n=11) strains in Odisha. The MDR strains from Sikkim demonstrated similar resistance profile of fluroquinolones and pair-wise SNP distances showed presence of local transmission clusters. We also detected significant enrichment of short INDELs in MDR samples in contrast to drug susceptible samples. This study provides molecular level insight into Mtb strains of eastern region in comparison with Indian and global perspective.

category: microbiology


title: Peptidoglycan maturation controls spatiotemporal organisation of outer membrane proteins in Escherichia coli

abstract: Linkages between the outer membrane of Gram-negative bacteria and the peptidoglycan layer are crucial to the maintenance of cellular integrity and enable survival in challenging environments1-5. The functionality of the outer membrane relies on outer membrane proteins (OMPs), which are inserted by the {beta}-barrel assembly machine, BAM6, 7. Previous work has shown that growing Escherichia coli cells segregate old OMPs towards the poles by an unknown mechanism8. Here, we demonstrate that peptidoglycan underpins the spatiotemporal organisation of OMPs. Mature, tetrapeptide-rich peptidoglycan binds to BAM components and suppresses OMP foldase activity. Nascent peptidoglycan, which is enriched in pentapeptides and concentrated at septa9, associates with BAM poorly and has little impact on its activity, leading to preferential insertion of OMPs at division sites. Synchronising OMP biogenesis to cell wall growth enables bacteria to replenish their OMPs by binary partitioning. Our study reveals that Gram-negative bacteria coordinate the assembly of two major cell envelope layers by rendering OMP biogenesis responsive to peptidoglycan maturation. This coordination offers new possibilities for the design of antibiotics that disrupt cell envelope integrity.


title: RNA-protein interactome at the Hepatitis E virus internal ribosome entry site

abstract:
Multiple processes exist in a cell to ensure continuous production of essential proteins either through cap-dependent or cap-independent translation processes. Viruses depend on the host translation machinery for viral protein synthesis. Therefore, viruses have evolved clever strategies to utilize the host translation machinery. Earlier studies have shown that genotype 1-Hepatitis E virus (g1-HEV) utilizes both cap-dependent and cap-independent translation machineries for its replication and proliferation. Cap-independent translation in g1-HEV is driven by an eighty seven nucleotide-long RNA element which acts as a noncanonical, internal ribosome entry site like (IRESl) element. Here, we have identified the RNA-protein interactome of the HEV IRESl element and characterized the functional significance of some of its components. Our study reveals indispensable roles of host ribosomal protein RPL5 and DHX9 (RNA helicase A) in mediating efficient translation from the IRESl element and establish the function of HEV IRESl as a bonafide internal ribosome entry site.

Author summaryProtein synthesis is a fundamental process for survival and proliferation of all living organisms. Majority of cellular proteins are produced through a cap-dependent translation process. However under conditions of stress and/or when cap-dependent translation is not operational, cells utilize a variety of cap-independent translation processes to synthesize essential proteins. Viruses are the only living organisms which depend on the host cell translation apparatus to synthesize their own proteins. Many viruses utilize both cap-dependent and cap-independent machineries for the synthesis of viral proteins. Hepatitis E virus is a major cause of acute hepatitis worldwide. The viral genome is a capped positive strand RNA. Viral non-structural and structural proteins are synthesized through a cap-dependent translation process from one open reading frame (ORF) present in the genomic RNA and two overlapping ORFs present in the subgenomic RNA, respectively. An earlier study from our laboratory reported the presence of a fourth ORF in the viral genome, which produced the ORF4 protein using a cap-independent internal translation initiation mechanism. Using bicistronic reporter assays and site-directed mutagenesis studies, it was demonstrated that translation of the ORF4 protein was driven by an internal ribosome entry site-like (IRESl) element. In the current study, we identified the host proteins that directly or indirectly associate with the HEV-IRESl RNA and generated the RNA-protein interactome. Subsequent studies identified essential roles of ribosome protein L5 (RPL5) and DHX9 (RNA Helicase A) in mediating the function of the IRESl. Biochemical fractionation studies showed the presence of IRESl and its components in the actively translating polysomes. Collectively, our data proves that HEV-IRESl is a bonafide internal ribosome entry site.


title: Toxoplasma scavenges mammalian host organelles through usurpation of host ESCRT-III and Vps4

abstract:
Intracellular pathogens exploit cellular resources through host cell manipulation. Within its nonfusogenic parasitophorous vacuole (PV), Toxoplasma targets host nutrient-filled organelles and sequesters them into the PV through deep invaginations of the PV membrane (PVM) that ultimately detach from this membrane. Some of these invaginations are generated by an intravacuolar network (IVN) of parasite-derived tubules fusing with the PVM. Here, we examine the parasite usurpation of host ESCRT-III and Vps4 to create PVM buds and vesicles. CHMP4B associates with the PVM/IVN and dominant negative (DN) CHMP4B forms many long PVM invaginations containing CHMP4B filaments; the invaginations are shorter in IVN-deficient parasites, suggesting cooperation between IVN and ESCRT. In infected cells expressing Vps4-DN, enlarged intra-PV structures containing host endo-lysosomes accumulate, reflecting defects in PVM scission. Parasite mutants lacking TgGRA14 or TgGRA64 that interact with ESCRT have reduced CHMP4B-DN-induced PVM invaginations and intra-PV host organelles, with greater defects in a double-knockout, revealing the exploitation of ESCRT to scavenge host organelles by Toxoplasma.

SummaryThe parasite Toxoplasma sequesters host nutrient-filled organelles into its parasitophorous vacuole through its exploitation of host ESCRT-III and Vps4 for vacuolar membrane-remodeling and fission processes utilizing the parasite proteins TgGRA14 and TgGRA64 that interact with ESCRT.


title: An electro-optical bead-nanochip technology for the ultrasensitive and multi-dimensional detection of small extracellular vesicles and their markers

abstract:
Small extracellular vesicles (sEVs), including exosomes, are enriched in multiomics information mirroring their parental cells. They have been investigated in health and disease and utilised in several applications from drug discovery to diagnostics. In disease diagnostics, sEVs can be sampled via a blood draw, enabling the convenient liquid biopsy of the tissue they originate from. However, few applications with sEVs have been translated into clinical practice.

We developed a Nanoparticle EXOsome Sensing (NEXOS) technology, for the ultrasensitive and multi-dimensional detection of sEVs. NEXOS comprises two methods: a novel nanoelectronics method, E-NEXOS, and a high-throughput optical detection method, O-NEXOS. Both methods share the same steps for the immunocapture and antibody-labelling of sEVs and can be combined to derive differentiated detection parameters.

As a proof of concept, we show the analytical detection and sensitivity of these methods in detecting pre-prepared cancer cell-derived CD9+CD81+ and CD9+HER2+ sEVs. Both sEV populations were diluted in PBS and spiked in processed plasma. We also provide a novel approach for the determination of target sEVs (TEVs), target epitopes in sEVs (TEPs), and epitopes per target sEV, as yet unseen from current and emerging technologies.

Further, we demonstrate the higher sensitivity of O-NEXOS compared to the gold standard techniques, as well as demonstrating that E-NEXOS possesses commensurate sensitivity whilst only being powered by 36 nanogap-based sensors per nanochip.

Finally, this manuscript lays the groundwork for a scalable electronics miniaturization of E-NEXOS nanochip with millions of nanogap-based sensors for the translation of NEXOS into standard clinical practice.

category: molecular biology


title: Quantitation of FGFR3 signaling via GRB2 recruitment on micropatterned surfaces

abstract:
Fibroblast growth factor receptors (FGFRs) initiate signal transduction via the RAS/MAPK pathway by their tyrosine-kinase activation known to determine cell-growth, tissue differentiation and apoptosis. Recently, many missense mutations have been reported for FGFR3, but we only know the functional effect for a handful of them. Some of these mutations result in aberrant FGFR3 signaling and are associated with various genetic disorders and oncogenic conditions. Here we employed micropatterned surfaces to specifically enrich fluorophore-tagged FGFR3 (mGFP-FGFR3) in certain areas of the plasma membrane of living cells. Receptor activation was then quantified via the recruitment of the downstream signal transducer GRB2 tagged with mScarlet (GRB2-mScarlet) to FGFR3 patterns. With this system, we tested the activation of FGFR3 upon ligand addition (fgf1 and fgf2) in the wildtype (WT), as well as in different FGFR3 mutants associated with congenital disorders (G380R, Y373C, K650Q, K650E). Our data showed that the addition of ligands increased GRB2 recruitment to WT FGFR3, with fgf1 having a stronger effect than fgf2. For all mutants, we found an increased basal receptor activity, and only for two of the four mutants (G380R and K650Q), activity was further increased upon ligand addition. Compared to previous reports, two mutant receptors (K650Q and K650E) had either an unexpectedly high or low activation state, respectively. This may be explained by the different receptor populations probed, since the micropatterning method specifically reports on signaling events at the plasma membrane.

Graphical AbstractSpecifications: The maximum size of the image should be 200 x 500 pixels with a minimum resolution of 300 dpi, using Arial font with a size of 10-16 points; Preferred file types: TIFF, EPS, PDF or MS Office files

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/487861v1_ufig1.gif" ALT="Figure 1">
View larger version (33K):
org.highwire.dtl.DTLVardef@4a279eorg.highwire.dtl.DTLVardef@6f35d1org.highwire.dtl.DTLVardef@13661e7org.highwire.dtl.DTLVardef@155b480_HPS_FORMAT_FIGEXP  M_FIG C_FIG Research HighlightsO_LIQuantification of FGFR3 signaling in live cells on micropatterned surfaces
C_LIO_LIAnalysis of GRB2 recruitment to the mature receptor at the plasma membrane
C_LIO_LILigand-independent kinase activation of FGFR3 mutants
C_LIO_LIActivation of FGFR3 at the cell surface can be different than in bulk cell extracts
C_LI


title: Multi-level monitoring of EME1-MUS81 in CPT induced nucleolar rDNA repair

abstract: We identified EME1, the regulatory subunit of the structure-specific endonuclease complex EME1-MUS81, as substrate for the sumoylated UBC9 and demonstrated synergistic functions in promoting Camptothecin (CPT)-induced nucleolar ribosomal DNA (rDNA) repair (Nagamalleswari et al, co-submitted). Sumoylation of EME1 appears complex involving mono- and poly-sumoylation. Hence, we addressed here whether these modifications differentially regulate EME1 functions by analyzing EME1-variant expressing cell lines including mono-sumo(1)ylation and poly-sumo(2)ylation mimetic fusions. We complemented our analysis with the regulated endogenous EME1 interactome and our observation that Trichostatin A (TSA) induced EME1 and UBC9 sumoylation. Our findings are substantiated by identifying several regulatory proteins and by detecting CPT-induced endogenous di- and poly-sumoylated EME1 in different cell fractions. Together, our data suggest that Histone H4 acetylation, two mono-sumoylation events, poly-sumoylation, ISG15 and ubiquitination sequentially and in mutual dependence tightly control the intracellular localization, recruitment to DNA lesions, enzymatic activity, withdrawal from DNA lesions and the stability of EME1.


title: An adaptive filtering framework for non-specific and inefficient reactions in multiplex digital PCR based on sigmoidal trends

abstract: Real-time digital PCR (qdPCR) coupled with artificial intelligence has shown the potential of unlocking scientific breakthroughs, particularly in the field of molecular diagnostics for infectious diseases. One of the most promising applications is the use of machine learning (ML) methods to enable single fluorescent channel PCR multiplex by extracting target-specific kinetic and thermodynamic information contained in amplification curves. However, the robustness of such methods can be affected by the presence of undesired amplification events and nonideal reaction conditions. Therefore, here we proposed a novel framework to filter non-specific and low efficient reactions from qdPCR data using outlier detection algorithms purely based on sigmoidal trends of amplification curves. As a proof-of-concept, this framework is implemented to improve the classification performance of the recently reported ML-based Amplification Curve Analysis (ACA), using available data from a previous publication where the ACA method was used to screen carbapenemase-producing organisms in clinical isolates. Furthermore, we developed a novel strategy, named Adaptive Mapping Filter (AMF), to consider the variability of positive counts in digital PCR. Over 152,000 amplification events were analyzed. For the positive reactions, filtered and unfiltered amplification curves were evaluated by comparing against melting peak distribution, proving that abnormalities (filtered out data) are linked to shifted melting distribution or decreased PCR efficiency. The ACA was applied to compare classification accuracies before and after AMF, showing an improved sensitivity of 1.18% for inliers and 20% for outliers (p-value < 0.0001). This work explores the correlation between kinetics of amplification curves and thermodynamics of melting curves and it demonstrates that filtering out non-specific or low efficient reactions can significantly improve the classification accuracy for cutting edge multiplexing methodologies.


title: Separation of phosphatase and kinase activity within the Bub complex is required for proper mitosis

abstract: The Bub1 and BubR1 kinetochore proteins support proper chromosome segregation and mitotic checkpoint activity. Bub1 and BubR1 are paralogues with Bub1 being a kinase while BubR1 localizes the PP2A-B56 protein phosphatase to kinetochores in humans. Whether this separation of kinase and phosphatase activity is important is unclear as some organisms integrate both activities into one Bub protein. Here we engineer human Bub1 and BubR1 proteins integrating kinase and phosphatase activities into one protein and show that these do not support normal mitotic progression. A Bub1-PP2A-B56 complex can supports chromosome alignment but results in impairment of the checkpoint due to dephosphorylation of the Mad1 binding site in Bub1. Furthermore, a chimeric BubR1 protein containing the Bub1 kinase domain induces delocalized H2ApT120 phosphorylation resulting in reduction of centromeric hSgo2 and chromosome segregation errors. Collectively, these results argue that the separation of kinase and phosphatase activities within the Bub complex is required for balancing its functions in the checkpoint and chromosome alignment.


title: A phenotypic screen of Marfan syndrome iPSC-derived vascular smooth muscle cells uncovers GSK3β as a new target

abstract: Marfan syndrome (MFS) is a rare connective tissue disorder caused by mutations in FBN1. Patients with MFS notably suffer from aortic aneurysm and dissection. Despite considerable effort, animal models have proven to be poorly predictive for therapeutic intervention in human aortic disease. Using a "humanised" model system may be more appropriate in identifying new therapeutic targets. Patient-derived induced pluripotent stem cells can be differentiated into vascular smooth muscle cells (VSMCs) and recapitulate major features of MFS. We have screened 1,022 small molecules in our in vitro model, exploiting the highly-proteolytic nature of MFS-VSMCs, and identified 36 effective compounds. Further analysis identified GSK3{beta} as a recurring target in the compound screen. GSK3{beta} inhibition/knockdown did not ameliorate the proliferation defect in MFS-VSMCs but improved MFS-VSMC apoptosis and proteolysis. To conclude, we have identified GSK3{beta} as a novel target for MFS, forming the foundation for future work in MFS and other aortic diseases.


title: Reduced affinity of calcium sensing-receptor heterodimers and reduced mutant homodimer trafficking combine to impair function in a mouse model of Familial Hypocalciuric Hypercalcemia Type 1

abstract: Heterozygous loss-of-function mutation of the calcium sensing-receptor (CaSR), causes familial hypocalciuric hypercalcemia type 1 (FHH1), a typically benign condition characterized by mild hypercalcemia. In contrast, homozygous mutation of this dimer-forming G-protein coupled receptor manifests as the lethal neonatal severe hyperparathyroidism (NSHPT). To investigate the mechanisms by which CaSR mutations lead to these distinct disease states, we engineered wild-type (WT) and an exon 5-deficient disease-causing mutation, and transfected expression constructs into human embryonic kidney (HEK) cells. WT protein was mainly membrane-expressed whereas the mutant CaSR protein (mCaSR) was confined to the cytoplasm. Co-expression of WT CaSR directed mCaSR to the cell membrane. In assays of CaSR function, increases in extracellular [Ca2+] ([Ca2+]o) increased intracellular [Ca2+] ([Ca2+]i) in cells expressing WT CaSR while the response was reduced in cells coexpressingmutant and WT receptor. Untransfected cells or those expressing mCaSR alone, showed minimal, equivalent responses to increased [Ca2+]o. Immunoprecipitation experiments confirmed an association between mutant and wild-type CaSR. The affinity of the WT CaSR for calcium was three times greater than that of the heterodimer. The maximal functional response to [Ca]o was dependent on localization of CaSR to the membrane level and independent of homo- or heterodimerizations. In summary, these results suggest that heterodimerization of WT and mCaSR receptors, rescues the trafficking defect of the mutant receptors and also reduces the affinity of the WT-mutant heterodimer for [Ca]o. In contrast, the homozygous mutants do not produce functional receptors on cell membrane. These data indicate how substantial differences between signaling of hetero- and homodimeric mutants lead to profound differences in the severity of disease in heterozygous and homozygous carriers of these mutations.


title: Gradients in cellular metabolism regulate development of tonotopy along the chick cochlea.

abstract: In vertebrates with elongated auditory organs, mechanosensory hair cells (HCs) are organised such that complex sounds are broken down into their component frequencies along the basal-to-apical long (tonotopic) axis. To generate the frequency-specific characteristics required at the appropriate positions, nascent HCs must determine their tonotopic properties during development. This relies on complex signalling between the developing HC and its local niche along the axis within the auditory organ. Here we apply NAD(P)H fluorescence lifetime imaging (FLIM) and live imaging of mitochondria to reveal metabolic gradients along the tonotopic axis of the developing cochlea. We further show that re-shaping these gradients during development, by inhibiting cytosolic glucose metabolism, alters normal Bmp7 and Chordin like-1 signalling leading to flattening of tonotopic patterning along the axis. Our work supports a causal link between morphogen signalling and metabolic reprogramming in specifying tonotopic morphologies in auditory HCs.

category: developmental biology


title: Gradients in cellular metabolism regulate development of tonotopy along the cochlea.


title: Phylotranscriptomics Reveals the Reticulate Evolutionary History of a Widespread Diatom Species Complex

abstract: In contrast to surveys based on a few genes that often provide limited taxonomic resolution, transcriptomes provide a wealth of genomic loci that can resolve relationships among taxonomically challenging lineages. Diatoms are a diverse group of aquatic microalgae that includes important bioindicator species and many such lineages. One example is Nitzschia palea, a widespread species complex with several morphologically based taxonomic varieties, some of which are critical pollution indicators. Morphological differences among the varieties are subtle and phylogenetic studies on a few genes fail to resolve their evolutionary relationships. We conducted morphometric and transcriptome analyses of 10 Nitzschia palea strains to resolve the relationships among strains and taxonomic varieties. Nitzschia palea was resolved into three clades, one of which corresponds to a group of strains with narrow linear-lanceolate valves. The other morphological group recovered in the shape outline analysis was not monophyletic and consisted of two clades. Subsequent gene-tree concordance analyses and phylogenetic network estimations revealed patterns of incomplete lineage sorting and gene flow between intraspecific lineages. We detected reticulated evolutionary patterns among lineages with different morphologies and a resulting putative recent hybrid. Our study shows that phylogenomic analyses of many unlinked nuclear loci, complemented with morphometrics, can resolve complex evolutionary histories of recently diverged species complexes.


title: Debugging and consolidating multiple synthetic chromosomes reveals combinatorial genetic interactions

abstract: The Sc2.0 project is building a eukaryotic synthetic genome from scratch, incorporating thousands of designer features. A major milestone has been achieved with the assembly of all individual Sc2.0 chromosomes. Here, we describe the consolidation of multiple synthetic chromosomes using endoreduplication intercross to generate a strain with 6.5 synthetic chromosomes. Genome-wide chromosome conformation capture and long-read direct RNA sequencing were performed on this strain to evaluate the effects of designer modifications, such as loxPsym site insertion, tRNA relocation, and intron deletion, on 3D chromosome organization and transcript isoform profiles. To precisely map "bugs", we developed a method, CRISPR Directed Biallelic URA3-assisted Genome Scan, or "CRISPR D-BUGS", exploiting directed mitotic recombination in heterozygous diploids. Using this method, we first fine-mapped a synII defect resulting from two loxPsym sites in the 3 UTR of SHM1. This approach was also used to map a combinatorial bug associated with synIII and synX, revealing a highly unexpected genetic interaction that links transcriptional regulation, inositol metabolism and tRNASerCGA abundance. "Starvation" for tRNASerCGA leads to insufficient levels of the key positive inositol biosynthesis regulator, Swi3, which contains tandem UCG codons. Finally, to expedite consolidation, we employed a new method, chromosome swapping, to incorporate the largest chromosome (synIV), thereby consolidating more than half of the Sc2.0 genome in a single strain.


title: An intrinsically disordered transcription activation domain alters the DNA binding affinity and specificity of NFκB p50/RelA

abstract: Many transcription factors contain intrinsically disordered transcription activation domains (TADs), which mediate interactions with co-activators to activate transcription. Historically, DNA-binding domains and TADs have been considered as modular units, but recent studies have shown that TADs can influence DNA binding. We biophysically characterized the NF{kappa}B p50/RelA heterodimer including the RelA TAD and investigated the TADs influence on NF{kappa}B-DNA interactions. In solution the RelA TAD is disordered but compact, with helical tendency in two regions that interact with co-activators. The presence of the TAD increased the stoichiometry of NF{kappa}B-DNA complexes containing promoter DNA sequences with tandem {kappa}B recognition motifs by promoting the binding of NF{kappa}B dimers in excess of the number of {kappa}B sites. We measured the binding affinity of p50/RelA for DNA containing tandem {kappa}B sites and single {kappa}B sites. While the presence of the TAD enhanced the binding affinity of p50/RelA for all {kappa}B sequences tested, it increased the affinity for non-specific DNA sequences by over 10-fold, leading to an overall decrease in specificity for {kappa}B DNA sequences. Our results reveal a novel function of the RelA TAD in promoting binding to non-consensus DNA previously observed by in vivo studies of NF{kappa}B-DNA binding in response to strong inflammatory signals.

category: biochemistry


title: Rational design by structural biology of industrializable, long-acting antihyperglycemic GLP-1 receptor agonists

abstract: Glucagon-like peptide-1 (GLP-1) is easily degraded by dipeptidyl peptidase-4 (DPP-4) in the human body, limiting its therapeutic effect on type II diabetes. Therefore, improving GLP-1 receptor agonist (GLP-1RA) stability is a major obstacle for drug development. We analyzed human GLP-1, DPP-4, and GLP-1 receptor structures and designed three GLP-1RAs, which were introduced into fusion protein fragments and changed in the overall conformation. This modification effectively prevented GLP-1RAs from entering DPP-4 active center without affecting GLP-1Ras ability to bind to GLP-1R, the new GLP-1RA hypoglycemic effect lasting for >24 h. Through molecular modeling, molecular dynamics calculation, and simulation, possible tertiary structure models of GLP-1RAs were obtained; molecular docking with DPP-4 and GLP-1R showed access to the fusion protein. The overall conformational change of GLP-1RAs prevented DPP-4 binding, without affecting GLP-1Ras affinity to GLP-1R. This study provides important drug design ideas for GLP-1RA development and a new example for application of structural biology-based protein design in drug development.


title: SARS-ANI: A Global Open Access Dataset of Reported SARS-CoV-2 Events in Animals

abstract: The zoonotic origin of SARS-CoV-2, the etiological agent of COVID-19, is not yet fully resolved. Although natural infections in animals are reported in a wide range of species, large knowledge and data gaps remain regarding SARS-CoV-2 animal hosts. We used two major health databases to extract unstructured data and generated a comprehensive global dataset of thoroughly documented SARS-CoV-2 events in animals. The dataset integrates relevant epidemiological and clinical data on each event and is readily usable for analytical purposes. We also share the code for technical and visual validation of the data and created a user-friendly dashboard for data exploration. Data on SARS-CoV-2 occurrence in animals is critical to adapt monitoring strategy, prevent the formation of animal reservoirs, and tailor future human and animal vaccination programs. The FAIRness and analytical flexibility of the data will support research efforts on SARS-CoV-2 at the human-animal-environment interface. We intend to update this dataset weekly for at least one year and, through collaborative processes, to develop the dataset further and expand its use.


title: Key mutations on spike protein altering ACE2 receptor utilization and potentially expanding host range of emerging SARS-CoV-2 variants

abstract: Increasing evidence supports inter-species transmission of SARS-CoV-2 variants from human to domestic or wild animals during the ongoing COVID-19 pandemic, which is posing great challenges to epidemic control. Clarifying the host range of emerging SARS-CoV-2 variants will provide instructive information for the containment of viral spillover. The spike protein (S) of SARS-CoV-2 is the key determinant of receptor utilization, and therefore amino acid mutations on S will probably alter viral host range. Here, in order to evaluate the impact of S mutations, we constructed 20 Hela cell lines stably expressing ACE2 orthologs from different animals, and prepared 27 pseudotyped SARS-CoV-2 carrying different spike mutants, among which 20 bear single mutation and the other 7 were cloned from emerging SARS-CoV-2 variants, including D614G, Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.135), Lambda (B.1.429) and Mu (B.1.525). Using pseudoviral reporter assay, we identified that the substitutions of T478I and N501Y enabled the pseudovirus to utilize chicken ACE2, indicating potential infectivity to avian species. Furthermore, the S mutants of real SARS-CoV-2 variants comprising N501Y showed significantly acquired abilities to infect cells expressing mouse ACE2, indicating a critical role of N501Y in expanding SARS-CoV-2 host range. In addition, A262S and T478I significantly enhanced the utilization of various mammals ACE2. In summary, our results indicated that T478I and N501Y substitutions were two S mutations important for receptor adaption of SARS-CoV-2, potentially contributing to spillover of the virus to many other animal hosts. Therefore, more attention should be paid to SARS-CoV-2 variants with these two mutations.


title: UBC9 and EME1 sumoylation foster ribosomal DNA damage repair in CPT response

abstract: UBC9 sumoylation (S*UBC9) in mammals contributes to SUMO target discrimination, biochemically1. Here, we present biological insights by characterizing a sumoylation mimetic UBC9-fusion (mCS~UBC9) in comparison to its wild-type (mCUBC9). We observe that sumoylation promotes UBC9s stability, nuclear localization and is beneficial for cell survival. We identified EME1, the regulatory subunit of the structure-specific endonuclease EME1-MUS81, as S*UBC9 substrate and demonstrate EME1 and UBC9 sumoylation being advantageous for survival upon Camptothecin (CPT) exposure. Moreover, mCS~UBC9 expression enhances double-strand breaks (DSBs) and replication upon CPT treatment, features assigned to the EME1-MUS81 complex2. EME1 and mCS~UBC9 co-localize in nucleolar repair-condensates, that enlarge and round when exposed to the drug. Together, these findings imply that S*UBC9-induced EME1 sumoylation improves ribosomal rDNA repair, which might prevent dangerous second template switches in highly repetitive ribosomal chromatin and allow the converging replication fork to complete DNA replication. Finally, we discuss implications of these findings for anti-cancer therapy.


title: Disrupting ACE2 Dimerization Mitigates the Infection by SARS-COV-2

abstract: The coronavirus disease 2019 (COVID-19) pandemic has caused over 6 million death and 460 million reported cases globally. More effective antiviral medications are needed to curb the continued spread of this disease. The infection by SARS-COV-2 virus is initiated via the interaction between the receptor binding domain (RBD) of the viral glycoprotein Spike (S protein) and the N-term peptidase domain (PD) of the angiotensin-converting enzyme 2 (ACE2) expressed on host cell membrane. ACE2 forms protein homodimer primarily through its ferredoxin-like fold domain (aka. Neck-domain). We investigated whether the dimerization of ACE2 receptor plays a role in SARS-COV-2 virus infection. We report here that the ACE2 receptor dimerization enhances the recognition of SARS-COV-2 S protein. A 43 amino acid peptide based on the N-term of Neck-domain could block the ACE2 dimerization and the interaction between RBD and ACE2, and mitigate the SARS-COV-2/host cell interaction. Our study illustrated a new route to develop potential therapeutics for the prevention and treatment of SARS-COV-2 viral infection.


title: A synthetic ancestral Kinesin-13 depolymerises microtubules faster than any natural depolymerising kinesin

abstract: The activity of a kinesin is largely determined by the ~350 residue motor domain and this region alone is sufficient to classify a kinesin as a member of a particular family. The Kinesin-13 family are a group of microtubule depolymerising kinesins and are vital regulators of microtubule length. Members of this family are critical to spindle assembly and chromosome segregation in both mitotic and meiotic cell division and play crucial roles in cilium length control and neuronal development. To better understand the evolution of microtubule depolymerisation activity in the Kinesin-13 family, we created a synthetic ancestral Kinesin-13 motor domain. This phylogenetically-inferred ancestral motor domain is the sequence predicted to have existed in the common ancestor of the Kinesin-13 family. Here we show that the ancestral Kinesin-13 motor depolymerises stabilised microtubules faster than any previously tested depolymerase. This potent activity is more than an order of magnitude faster than the most highly studied Kinesin-13, MCAK and allows the ancestral Kinesin-13 to depolymerise doubly-stabilised microtubules that are unaffected by MCAK. These data suggest that the ancestor of the Kinesin-13 family was a  super depolymeriser and that members of the Kinesin-13 family have evolved away from this extreme depolymerising activity to provide more controlled microtubule depolymerisation activity in extant cells.


title: Autophagy Increases Occludin Levels to Enhance Intestinal Paracellular Tight Junction Barrier.

abstract:
Background and AimFunctional loss of paracellular tight junction (TJ) barrier of the gut epithelium and mutations in autophagy genes are factors potentiating inflammatory bowel disease (IBD). Previously we showed the role of autophagy in enhancing the TJ barrier via claudin-2 degradation, however, its role in the regulation of the barrier-forming protein occludin remains unknown. Here, we investigate the role of autophagy in the regulation of occludin and its role in inflammation-mediated TJ barrier loss.

MethodsPharmacological and genetic tools were used to study the effect of autophagy on occludin levels and localization, and the role of the MAPK pathway.

ResultsAutophagy induction using pharmacological activators and nutrient starvation increased total occludin levels in different epithelial cells. Starvation enriched membrane occludin levels and reduced paracellular inulin flux in Caco-2 cells. Starvation-induced TJ barrier enhancement was contingent on the presence of occludin as OCLN-/- nullified its TJ barrier enhancing effect. Autophagy inhibited the constitutive degradation of occludin and protected against inflammation-induced TJ barrier loss. Starvation-induced TJ barrier enhancement was prevented by inhibition of autophagy. Autophagy enhanced the phosphorylation of ERK-1/2. Inhibition of these kinases in Caco-2 cells and human intestinal mucosa inhibited the protective effects of autophagy. In-vivo, autophagy induction by rapamycin increased occludin levels in mouse intestines and protected against LPS and TNF--induced TJ barrier loss. Additionally, acute Atg7 knockout in adult mice decreased intestinal occludin levels, increasing baseline colonic TJ-permeability and exacerbating the effect of DSS-induced colitis.

ConclusionOur data suggest a novel role of autophagy in promoting the intestinal TJ barrier by increasing occludin levels in an ERK1/2 MAPK-dependent mechanism.

Graphical abstract

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title: Receptor binding domain of SARS-CoV-2 is a functional αv-integrin agonist

abstract: Among the novel mutations distinguishing SARS-CoV-2 from similar respiratory coronaviruses is a K403R substitution in the receptor-binding domain (RBD) of the viral spike (S) protein within its S1 region. This amino acid substitution occurs near the angiotensin-converting enzyme 2 (ACE2)-binding interface and gives rise to a canonical RGD adhesion motif that is often found in native extracellular matrix proteins, including fibronectin. In the present study, the ability of recombinant S1-RBD to bind to cell surface integrins and trigger downstream signaling pathways was assessed and compared to RGD-containing, integrin-binding fragments of fibronectin. S1-RBD supported adhesion of both fibronectin-null mouse embryonic fibroblasts as well as primary human small airway epithelial cells. Cell adhesion to S1-RBD was cation- and RGD-dependent, and was inhibited by blocking antibodies against v and {beta}3, but not 5 or {beta}1, integrins. Similarly, direct binding of S1-RBD to recombinant human v{beta}3 and v{beta}6 integrins, but not 5{beta}1 integrins, was observed by surface plasmon resonance. Adhesion to S1-RBD initiated cell spreading, focal adhesion formation, and actin stress fiber organization to a similar extent as fibronectin. Moreover, S1-RBD stimulated tyrosine phosphorylation of the adhesion mediators FAK, Src, and paxillin, Akt activation, and supported cell proliferation. Together, these data demonstrate that the RGD sequence within S1-RBD can function as an v-selective integrin agonist. This study provides evidence that cell surface v-containing integrins can respond functionally to spike protein and raise the possibility that S1-mediated dysregulation of ECM dynamics may contribute to the pathogenesis and/or post-acute sequelae of SARS-CoV-2 infection.


title: Critical Role of Insertion Preference for Invasion Trajectory of Transposons

abstract: Transposable elements (TEs) are mobile DNA sequences that have been highly successful at invading eukaryotic genomes. It is unclear how TE families reach high copy number given the expectation that some novel insertions will be deleterious. It has been hypothesized that TE families may evolve to target and insert into specific DNA sequences to adjust the underlying distribution of fitness effects for new insertions. Preferentially inserting into neutral sites could minimize the cumulative deleterious load of a TE family, allowing the mean TE copy number to increase with less risk for host population extinction. To test this hypothesis, we constructed simulations to explore how the transposition probability and insertion preference of a TE family influence the evolution of mean TE copy number and host population size, allowing for extinction. We find that extinction is most common in our simulations under high transposition probabilities, but, as we reduce transposition rates, the risk of extinction persists while the preference for neutral insertion sites is high. In the absence of mechanisms that regulate TE transposition, a preference for neutral insertion sites is not protective and, in fact, actively accelerates both an increase in TE copy number and the time to population extinction.

category: evolutionary biology


title: Exploring the mobilome and resistome of Enterococcus faecium in a One Health context across two continents

abstract: Enterococcus faecium is a ubiquitous opportunistic pathogen that is exhibiting increasing levels of antimicrobial resistance (AMR). Many of the genes that confer resistance and pathogenic functions are localized on mobile genetic elements (MGEs), which facilitate their transfer between lineages. Here, features including resistance determinants, virulence factors, and MGEs were profiled in a set of 1273 E. faecium genomes from two disparate geographic locations (in the UK and Canada) from a range of agricultural, clinical, and associated habitats. Neither lineages of E. faecium nor MGEs are constrained by geographic proximity, but our results show evidence of a strong association of many profiled genes and MGEs with habitat. Many features were associated with a group of clinical and municipal wastewater genomes that are likely forming a new human-associated ecotype. The evolutionary dynamics of E. faecium make it a highly versatile emerging pathogen, and its ability to acquire, transmit, and lose features presents a high risk for the emergence of new pathogenic variants and novel resistance combinations. This study provides a workflow for MGE-centric surveillance of AMR in Enterococcus that can be adapted to other pathogens.


title: Fatty sweet symphony: Decoding distinct ganglioside patterns of native and differentiated mesenchymal stem cells by a novel glycolipidomics profiling strategy

abstract: Gangliosides are an indispensable glycolipid class concentrated on cell surfaces with a critical role in stem cell differentiation. Nonetheless, owing to the lack of suitable methods for scalable analysis covering the full scope of ganglioside molecular diversity, their mechanistic properties in signaling and differentiation remain undiscovered to a large extent. This work introduces a sensitive and comprehensive ganglioside assay based on liquid chromatography, high-resolution mass spectrometry, and multistage fragmentation. Complemented by an open-source data evaluation workflow, we provide automated in-depth lipid species-level and molecular species-level annotation based on decision rule sets for all major ganglioside classes. Compared to conventional state-of-the-art methods, the presented ganglioside assay offers (1) increased sensitivity, (2) superior structural elucidation, and (3) the possibility to detect novel ganglioside species. A major reason for the highly improved sensitivity is the optimized spectral readout based on the unique capability of two parallelizable mass analyzers for multistage fragmentation. In addition to the significant technological advance, we identified 263 ganglioside species including cell-state-specific markers and previously unreported gangliosides in native and differentiated human mesenchymal stem cells. A general increase of the ganglioside numbers upon differentiation was observed as well as cell-state-specific clustering based on the ganglioside species patterns. By proving the predictive power of gangliosides as ubiquitous cell state-specific markers, we demonstrated the high throughput universal capability of our novel analytical strategy, which comes with new insights on the biological role of gangliosides in stem cell differentiation. Our analytical workflow will pave the way for new ganglioside- and glycolipid-based clusters of differentiation markers to determine stem cell phenotypes.


title: Preclinical evaluation of CDK4 phosphorylation predicts high sensitivity of malignant pleural mesotheliomas to CDK4/6 inhibition

abstract: Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited therapeutic options. In this study, we evaluated the impact of CDK4/6 inhibition by palbociclib in a panel of 28 MPM cell lines, including 19 patient-derived cell lines, using a variety of approaches including RNA-sequencing. Palbociclib used alone sufficed to strongly and durably inhibit the proliferation of 23 MPM cell lines, indicating a unique sensitivity of MPM to CDK4/6 inhibition. Importantly, insensitivity to palbociclib was mostly explained by the lack of active T172-phosphorylated CDK4. This was associated with the high p16INK4A (CDKN2A) levels that accompany RB1 defects or inactivation, and also (unexpectedly) cyclin E1 over-expression in the presence of wild-type RB1. Prolonged treatment with palbociclib irreversibly inhibited proliferation despite re-induction of cell cycle genes upon drug washout. A senescence-associated secretory phenotype including various potentially immunogenic components was also irreversibly induced. Phosphorylated CDK4 was detected in 80% of 47 MPM tumors indicating their intrinsic sensitivity to CDK4/6 inhibitors. The absence of this phosphorylation in some highly proliferative MPM tumors was linked to partial deletions of RB1, leading to very high p16 (CDKN2A) expression. Our study strongly supports the clinical evaluation of CDK4/6 inhibitory drugs for MPM treatment, in monotherapy or combination therapy.

category: cancer biology


title: A diet-independent zebrafish model for NAFLD recapitulates patient lipid profiles and offers a system for small molecule screening

abstract: Non-alcoholic Fatty Liver Disease (NAFLD) or pathological hepatic lipid overload, is considered to affect obese individuals. However, NAFLD in lean individuals is prevalent, especially in South Asian population. The pathophysiology of lean NAFLD is not well understood and most animal models of NAFLD use the high-fat diet paradigm. To bridge this gap, we have developed a diet-independent model of NAFLD in zebrafish. We have previously showed that chronic systemic inflammation causes metabolic changes in the liver leading to hepatic fat accumulation in an IL6 overexpressing (IL6-OE) zebrafish model. In the present study, we compared the hepatic lipid composition of adult IL6-OE zebrafish to the controls and found an accumulation of saturated triacylglycerols and a reduction in the unsaturated triacylglycerol species reminiscent of NAFLD patients. Zebrafish is an ideal system for chemical genetic screens. We tested whether the hepatic lipid accumulation in the IL6-OE is responsive to chemical treatment. We found that PPAR-gamma agonist Rosiglitazone, known to reduce lipid overload in the high fat diet models of NAFLD, could ameliorate the fatty liver phenotype of the IL6-OE fish. Rosiglitazone treatment reduced the accumulation of saturated lipids and showed a concomitant increase in unsaturated TAG species in our inflammation-induced NAFLD model. Our observations suggest that the IL6-OE model can be effective for small molecule screening to identify compounds that can reverse hepatic lipid accumulation, especially relevant to lean NAFLD.

category: pharmacology and toxicology


title: Long non-coding RNA G23Rik attenuates fasting-induced lipid accumulation in the liver

abstract:
Peroxisome proliferator-activated receptor  (PPAR) is a key mediator of lipid metabolism and metabolic stress in the liver. A recent study revealed that PPAR-dependent long non-coding RNAs (lncRNAs) play an important role in modulating metabolic stress and inflammation in the livers of fasted mice. Here hepatic lncRNA 3930402G23Rik (G23Rik) was found to have active peroxisome proliferator response elements (PPREs) within its promoter and is directly regulated by PPAR. Although G23Rik RNA was expressed to varying degrees in several tissues, the PPAR-dependent regulation of this lncRNA was only observed in the liver. Pharmacological activation of PPAR induced PPAR recruitment at the G23Rik promoter and a pronounced increase in hepatic G23Rik lncRNA expression. A G23Rik-null mouse line was developed to further characterize the function of this lncRNA in the liver. G23Rik-null mice were more susceptible to hepatic lipid accumulation in response to acute fasting. Histological analysis further revealed a pronounced buildup of lipid droplets and a significant increase in neutral triglycerides and lipids as indicated by enhance oil red O staining of liver sections. Hepatic cholesterol, non-esterified fatty acid, and triglyceride levels were significantly elevated in G23Rik-null mice and associated with induction of the lipid-metabolism related gene Cd36. These findings provide evidence for a lncRNA dependent mechanism by which PPAR attenuates hepatic lipid accumulation in response to metabolic stress through lncRNA G23Rik induction.

Key pointsO_LI3930402G23Rik (G23Rik) is a liver-enriched long non-RNA.
C_LIO_LIG23Rik is a PPARA target gene.
C_LIO_LILoss of G23Rik increases hepatic lipid accumulation during fasting
C_LI

category: physiology


title: Elp1 is required for development of visceral sensory peripheral and central circuitry

abstract:
Cardiovascular instability and a blunted respiratory drive in hypoxic conditions, are hallmark features of the genetic sensory and autonomic neuropathy, familial dysautonomia (FD). FD results from a mutation in the gene ELP1, whose encoded protein is a scaffolding subunit of the six subunit Elongator complex. In mice, we and others have shown that Elp1 is essential for the normal development of neural crest derived-dorsal root ganglia (DRG) sensory neurons. Whether Elp1 is also required for development of ectodermal placode-derived visceral sensory receptors which are required for normal baroreception and chemosensory responses, has not been investigated. Using mouse models for FD, our data indicate that in fact the entire circuitry underlying baroreception and chemoreception is impaired due to a requirement for Elp1 not only in the visceral sensory neuron ganglia, but also for normal peripheral target innervation, and in their CNS synaptic partners in the medulla. Thus Elp1 is required in both placode- and neural crest-derived sensory neurons and its reduction aborts the normal development of neuronal circuitry essential for autonomic homeostasis and interoception.

Summary statementDue to faulty afferent sensory signaling, patients with Familial dysautonomia (FD) have a diminished sensory arm of the baroreflex which would normally modulate blood pressure, and they have a blunted response to hypoxia and hypercapnia (Norcliffe-Kaufmann et al. 2010). Using mouse models for FD, we reveal here the underlying pathology which may underlie these severely impaired homeostatic reflex pathways in FD.


title: A population of gray matter oligodendrocytes directly associates with the vasculature

abstract: Oligodendrocyte lineage cells interact with the vasculature in the gray matter. Physical and functional interactions between blood vessels and oligodendrocyte precursor cells play an essential role in both the developing and adult brain. Oligodendrocyte precursor cells have been shown to migrate along the vasculature and subsequently detach from it during their differentiation to oligodendrocytes. However, the association of mature oligodendrocytes with blood vessels has been noted since the discovery of this glial cell type almost a century ago and this interaction remains poorly explored. Here, we systematically investigated the extent of mature oligodendrocyte interaction with the vasculature in mouse. We found that ~17% of oligodendrocytes were in contact with blood vessels in cortex, hippocampus and cerebellum. Contacts were made mainly with capillaries and sparsely with larger arterioles or venules. By combining light and serial electron microscopy, we demonstrated that oligodendrocytes are in direct contact with the vascular basement membrane, raising the possibility of direct signaling pathways and metabolite exchange with endothelial cells. During experimental remyelination in the adult, oligodendrocytes were regenerated and associated with blood vessels in the same proportion compared to control cortex, suggesting a homeostatic regulation of the vasculature-associated oligodendrocyte population. Based on the frequent and close association with blood vessels, we propose that vasculature-associated oligodendrocytes should be considered as an integral part of the vasculature microenvironment. This particular location could underlie specific functions of vasculature-associated oligodendrocytes, while contributing to the vulnerability of mature oligodendrocytes in neurological diseases.


title: INRI-seq enables global cell-free analysis of translation initiation and off-target effects of antisense inhibitors

abstract: Ribosome profiling (Ribo-seq) is a powerful method for the transcriptome-wide assessment of protein synthesis rates and the study of translational control mechanisms. Yet, Ribo-seq also has limitations. These include difficulties with detection of low abundance transcripts and analysis of translation-modulating molecules such as antibiotics, which are often toxic or challenging to deliver into living cells. Here, we have developed in vitro Ribo-seq (INRI-seq), a cell-free method to analyze the translational landscape of a fully customizable synthetic transcriptome. Using Escherichia coli as an example, we show how INRI-seq can be used to analyze the translation initiation sites of a transcriptome of interest. We also study the global impact of direct translation inhibition by antisense peptide nucleic acid (PNA) to analyze PNA off-target effects. Overall, INRI-seq presents a scalable, sensitive method to study translation initiation in a transcriptome-wide manner without the potentially confounding effects of extracting ribosomes from living cells.


title: Low-cost genomics enable high-throughput isolate screening and strain-level microbiome profiling

abstract: Earths environments harbor complex consortia of microbial lineages that affect processes ranging from host health to biogeochemical cycles. However, understanding the evolution and function of these microbiota has been limited by an inability to isolate individual microbial constituents and assemble their complete genomes in a high-throughput manner. Here, we present a workflow for bacterial isolation and whole-genome sequencing from complex microbiota using open-source labware and the OpenTrons automated liquid handling robotics platform. Our approach circumvents the need for isolate screening (e.g., through 16S rDNA sequencing or mass spectrometry analyses) by reducing the costs of genome-sequencing to ~$10 per bacterium. Applying the workflow, we quantified genomic diversity within 45 bacterial species in the chimpanzee gut microbiota. Results revealed hotspots of recombination in bacterial genomes and elevated transmission of plasmids between distantly related bacterial species within individual chimpanzee hosts. This study develops and applies an approach for high-throughput bacterial isolation and genome sequencing, enabling population genetic analyses of bacterial strains within complex communities not currently possible with metagenomic data alone.


title: Trascriptome meta-analysis of microalga Dunaliella tertiolecta under stress condition

abstract: Microalgae are photosynthetic organisms, which are considered as a potential source for sustainable metabolite production. Furthermore, stress conditions can affect metabolite production. In this study, a meta-analysis of RNA-seq experiments was performed to evaluate the response of metabolite biosynthesis pathways in Dunaliella tertiolecta to abiotic stress conditions, including high light, nitrogen deficiency, and high salinity. The results indicated down-regulation of light reaction, photorespiration, tetrapyrrole, and lipid-related pathways in salt stress. In comparison to salt stress, nitrogen deficiency mostly induced light reaction and photorespiration metabolisms. The up-regulation of phosphoenolpyruvate carboxylase, phosphoglucose isomerase, bisphosphoglycerate mutase, and glucose-6-phosphate-1-dehydrogenase (involved in central carbon metabolism) was observed under salt, high light, and nitrogen stress conditions. Interestingly, the results indicated that the meta-genes (i.e., modules of genes strongly correlated) tended to be located in a hub of stress-specific PPI (Protein-Protein Interaction) networks. Module enrichment of meta-genes PPI networks highlighted the cross talk between photosynthesis, fatty acids, starch, and sucrose metabolism under multiple stress conditions. Moreover, it was observed that the coordinated expression of the tetrapyrrole intermediated with meta-genes involved in starch biosynthesis. The results of the present study also showed that some pathways such as vitamin B6 metabolism, methane metabolism, ribosome biogenesis, and folate biosynthesis responded to different stress factors specifically. In conclusion, the results of this study revealed the main pathways underlying the abiotic stress responses for optimized metabolite production by the microalga Dunaliella in future studies. PRISMA check list was also included in the study.


title: Two-photon microscopy in vivo reveals brain vessel type-specific loss of glycocalyx caused by apoM/S1P signaling impairment.

abstract: Increases in adsorptive mediated transcytosis (AMT) at the blood-brain barrier (BBB) are linked to many brain disorders. In a healthy brain, AMT is suppressed by sphingosine-1-phosphate (S1P) receptor 1 (S1PR1) signaling. Low levels of S1P lead to a rise in AMT, but the mechanisms are incompletely understood. Here, we explored whether the rises in AMT are caused by the loss of the endothelial glycocalyx (gcx). We used two-photon microscopy in mice with low S1P plasma levels (Apom-/-) and developed a novel photobleaching approach to measure gcx in vivo at distinct classes of cerebral microvessels, i.e., arterioles, capillaries and venules. We show that S1P signaling impairment reduced gcx in arterioles but not in other vessel segments. The location of gcx loss corresponded to the vascular topology of AMT increases. The S1PR1 agonist SEW2871 restores low levels of AMT in Apom-/- mice but did not restore the gcx within the same time window. We propose that while the gcx loss may contribute to AMT increase, restoring gcx is not necessary for AMT to return to normal. These data establish a new imaging method to study gcx in the living mouse brain, demonstrate zonation of gcx in cerebral microvessels, and suggest differences in vascular susceptibility to gcx loss in disease states.


title: Hypervoxels: A Multidimensional Framework For The Representation And Analysis Of Neuroimaging Data

abstract: Most neuroimaging modalities use regular grids of voxels to represent the three-dimensional space occupied by the brain. However, a regular 3D voxel grid does not reflect the anatomical and topological complexity represented by the brains white matter connections. In contrast, tractography reconstructions based on diffusion MRI provide a closer characterisation of the white matter pathways followed by the neuronal fibres interconnecting different brain regions. In this work, we introduce hypervoxels as a new methodological framework that combines the spatial encoding capabilities of multidimensional voxels with the anatomical and topological information found in tractography data. We provide a detailed description of the framework and evaluate the benefits of using hypervoxels by carrying out comparative voxel and hypervoxel cluster inference analyses on diffusion MRI data from a neuroimaging study on amyotrophic lateral sclerosis (ALS). Compared to the voxel analyses, the use of hypervoxels improved the detection of effects of interest in the data in terms of statistical significance levels and spatial distribution across white matter regions known to be affected in ALS. In these regions, the hypervoxel results also identified specific white matter pathways that resolve the anatomical ambiguity otherwise observed in the results from the voxel analyses. The observed increase in sensitivity and specificity can be explained by the superior ability of hypervoxel-based methods to represent and disentangle the anatomical overlap of white matter connections. Based on this premise, we expect that the use of hypervoxels should improve the analysis of neuroimaging data when the effects of interest under investigation are expected to be aligned along distinct but potentially overlapping white matter pathways.


title: The specific roles of renal macrophages in monitoring and clearing off intratubular particles

abstract: During the filtrate of the glomerulus flows though the renal tubular system, a variety of microscopic sediment particles, including mineral crystals resulting from urine concentration, are generated. Dislodging these particles in the intratubular compartment is critical to ensure free flow of filtrate and the final formation of urine. However, the underlying mechanism for the clearance is unclear. Here, using high-resolution microscopy, we uncovered that the juxtatubular macrophages in the medulla constitutively formed transepithelial protrusions and were "sampling" urine contents. These behaviors were strengthened in the development of nephrolithiasis. In particular, the juxtatubular macrophages were efficient in sequestering and phagocytosing intraluminal sediment particles, and occasionally making transmigration to the tubule lumen to escort the excretion of urine particles. Specific depletion of renal macrophages precipitated kidney stone formation and aggravated the accompanied inflammation upon hyperoxaluria challenge. Thus, renal macrophages undertake a specific role in maintaining the tubular system unobstructed.

category: immunology


title: Expansion of Ventral Foregut Primes the Enhancer Landscape for Organ Specific Differentiation

abstract: Cell proliferation is fundamental for almost all stages of development and differentiation that require an increase cell number. Although cell cycle phase has been associated with differentiation, the actual process of proliferation is not seen as having a specific role. Here we exploit human embryonic stem cell derived endodermal progenitors that we find are an in vitro model for the ventral foregut. These cells exhibit expansion dependent increases in differentiation efficiency to pancreatic progenitors that are linked to organ-specific enhancer priming at the level of chromatin accessibility and the decommissioning of lineage inappropriate enhancers. Our findings suggest that cell proliferation in embryonic development is about more than tissue expansion, it is required to ensure equilibration of gene regulatory networks allowing cells to become primed for future differentiation. The use of expansion of lineage specific intermediates may therefore be an important step in high fidelity in vitro differentiation.


title: Wake respirometry may quantify stress and energetics of free-living animals

abstract: Quantifying activity-specific energy expenditure in free-living animals is a major challenge as current methods require calibration in the lab and animal capture. We propose "wake respirometry", a new method of quantifying fine-scale changes in CO2 production in unrestrained animals, using a non-dispersive infrared CO2 sensor positioned downwind of the animal i.e. in its wake. We parameterise the dispersion of CO2 in a wake using known CO2 concentrations, flow rates and wind speeds. Tests with three bird species in a wind tunnel demonstrated that the system can resolve breath-by-breath changes in CO2 concentration, with clear exhalation signatures increasing in period and integral with body size. Changes in physiological state were detectable following handling, flight and exposure to a perceived threat. We discuss the potential of wake respirometry to quantify stress and respiratory patterns in wild animals and estimate activity-specific metabolic rates through the full integration of CO2 production across the wake.


title: The influence of biotic and abiotic drivers on arthropod co-occurrence network topology in native forest remnants in the Azores

abstract:
Island biota are in imminent threat from anthropogenic impacts. Of these impacts the negative effects of exotic species on the taxonomic and functional diversity of the local fauna are of particularly major concern. Aside from their impact on the diversity of native fauna, exotics may also have a detrimental effect on native interactions which, in turn, can destabilise ecological networks. Species co-occurrence networks are used to predict ecological interaction networks and utilised as tools to assess environmental impacts on community structure. Here, we investigate the topological differences of the arthropod co-occurrence networks among native forest fragments from seven Azorean islands and reveal the influence of the abiotic environment and exotic species on these networks. We found that co-occurrence networks were sensitive to environmental and community dissimilarities, showing a clear separation between islands and pinpointed differences between indigenous and exotic networks. Most exotics are little connected and exotic networks have a large proportion of unconnected species. The resulting decreased connectance and the increased modularity with the increase of the proportions of exotics in the networks suggests that most exotics have too low prevalence to show associations with other species, and only a few dominants drive co-occurrences. Moreover, the proportion of negative links, as indicators of competition, did not increase with the increase of exotics in the habitats, suggesting that exotics occupied empty niches when they colonised native forest remnants. However, when the theoretical networks consisting of only indigenous species were investigated both the number of negative associations and modularity increased with the increase of exotics, suggesting obscure competition and processes of network degradation. Since our study provides ample evidence for the usefulness of co-occurrence network analysis in studying island ecosystems, we recommend the use of this tool for ecosystem assessments, early warning systems and decision making in island biodiversity conservation.

Significance statementGlobal anthropogenic biodiversity decline affects islands to a disproportionately greater extent than other ecosystems. One major cause of declining island biodiversity is the spread of exotic species which may overcompete and replace native biota. In this study, we show, by using arthropod species co-occurrence networks from the Azorean archipelago, that species association patterns reflect both abiotic and biotic impacts and that the increasing proportion of exotics in an ecosystem seemingly has little impact on association networks at large. However, when the effects on the association network of solely indigenous species were scrutinised, signs of network degradation were observed, suggesting an obscure, and most likely slow, negative impact of exotics on native arthropod assemblages. This disintegration of the co-occurrence networks can be the first sign of disappearing interaction links which, in turn, may jeopardise ecosystem function and can lead to regime shifts. In this work, we used a unique long-term dataset collected across the islands of the Azorean archipelago with standardised methodology. We built on the deep knowledge gathered over two decades on the ecology of species, as well as on the ongoing processes shaping the islands arthropod fauna, yet took a novel methodological approach and disentangled hidden ecological processes of great ecological and conservation concern.


title: The conservation of human functional variants and their effects across mammals

abstract: Despite the clear potential of livestock models of human functional variants to provide important insights into the biological mechanisms driving human diseases and traits, their use to date has been limited. Generating such models via genome editing is costly and time consuming, and it is unclear which variants will have conserved effects across species. In this study we address these issues by studying naturally occurring livestock models of human functional variants. We show that orthologues of over 1.6 million human variants are already segregating in domesticated mammalian species, including several hundred previously directly linked to human traits and diseases. Models of variants linked to particular phenotypes, including metabolomic disorders and height, have been preferentially maintained across species, meaning studying the genetic basis of these phenotypes is particularly tractable in livestock. Using machine learning we demonstrate it is possible to identify human variants that are more likely to have an existing livestock orthologue, and, importantly, we show that the effects of functional variants are often conserved in livestock, acting on orthologous genes with the same direction of effect. Consequently, this work demonstrates the substantial potential of naturally occurring livestock carriers of orthologues of human functional variants to disentangle their functional impacts.

category: genetics


title: The synaptonemal complex controls cis- versus trans-interference in coarsening-based meiotic crossover patterning

abstract: The shuffling of genetic material facilitated by meiotic crossovers is a critical driver of genetic variation. Therefore, the number and positions of crossover events must be carefully controlled. In Arabidopsis, an obligate crossover and repression of nearby crossovers on each chromosome pair are abolished in mutants that lack the synaptonemal complex (SC), a conserved protein scaffold. We use mathematical modelling and quantitative super-resolution microscopy to explore and mechanistically explain meiotic crossover pattering in Arabidopsis zyp1 mutants, that lack an SC. We develop an SC mutant coarsening model in which crossover precursors globally compete for a limited pool of the pro-crossover factor HEI10, with dynamic HEI10 exchange mediated through the nucleoplasm. We demonstrate that this model is capable of quantitatively reproducing and predicting experimental crossover patterning and HEI10 foci intensity data. Our results reveal that regulation of the number of crossovers within a cell in SC mutants ("trans-interference"), and inhibition of nearby crossovers on the same chromosome in wild-type cells ("cis-interference"), likely act through the same underlying coarsening mechanism, differing only in the spatial compartment through which the pro-crossover factor diffuses. The spatial compartment used is controlled by the SC, which therefore acts as a critical regulator of cis- versus trans-interference.


title: scTAM-seq enables targeted high-confidence analysis of DNA methylation in single cells

abstract: Single-cell DNA methylation profiling currently suffers from excessive noise and/or limited cellular throughput. We developed scTAM-seq, a targeted bisulfite-free method for profiling up to 650 CpGs in up to 10,000 cells per experiment, with a dropout rate of less than seven percent. scTAM-seq focuses sequencing coverage on informative, variably methylated CpGs that in many tissues and cell types make up a minor fraction of all CpGs. By applying scTAM-seq to B cells from blood and bone marrow, we demonstrate that it can resolve DNA methylation dynamics across B-cell differentiation at unprecedented resolution, identifying intermediate differentiation states that were previously masked. scTAM-seq additionally queries surface protein expression and somatic mutations, thus enabling integration of single-cell DNA methylation information with cell atlas data, and opening applications in tumor profiling. In summary, scTAM-seq is the first high-throughput, high-confidence method for analyzing DNA methylation at single-CpG resolution across thousands of single cells.


title: Extended Brain Sources Estimation via Unrolled Optimization Neural Network

abstract: Electroencephalography (EEG)/Magnetoencephalography (MEG) source imaging aims to seek an estimation of underlying activated brain sources to explain the observed EEG/MEG recording. Due to the ill-posed nature of inverse problem, solving EEG/MEG Source Imaging (ESI) requires design of regularization or prior terms to guarantee a unique solution. Traditionally, the design of regularization terms is based on preliminary assumptions on the spatio-temporal structure in the source space. In this paper, we propose a novel paradigm to solve the ESI problem by using Unrolled Optimization Neural Network (UONN) (1) to improve the efficiency compared to traditional iterative algorithms; (2) to establish a data-driven way to model the source solution structure instead of using hand-crafted regularizations; (3) to learn the hyperparameter automatically in a data-driven manner. The proposed framework is based on unfolding of the iterative optimization algorithm with neural network modules. The proposed new learning framework is the first one that use the unrolled optimization neural network to solve the ESI problem. The newly designed framework can effectively learn the source extents pattern and achieved significantly improved performance compared to benchmark algorithms.


title: Intradiscal Inflammatory Stimulation Induces Spinal Pain Behavior and Intervertebral Disc Degeneration In Vivo

abstract: Degeneration of the intervertebral disc (IVD) is known to occur naturally over time, with the severity of pain varying widely. Other components of the degenerative environment, including structural disruption and inflammatory cytokine levels, and their correlation with pain severity have been studied. However, the role of the inflammatory environment in activating degenerative changes that manifest as a pain phenotype has not been elucidated. Previous studies have aimed to recreate the sustained inflammatory environment exhibited during human disc degeneration in a rat model. Most commonly, a puncture injury has been used causing structural damage and only initiating an acute inflammatory response. This study utilized injection of lipopolysaccharide (LPS), a pro-inflammatory stimulus, into the rat disc in vivo to create the desired sustained inflammatory environment independent of physical disruption. LPS injections resulted in upregulation of pro-inflammatory cytokines and an immunogenic response. The structural integrity of the IVD was also altered demonstrated by changes in histological score, disc height, and mechanical properties. Ultimately, a sustained inflammatory environment led to both local and radiating mechanical sensitivity, demonstrating that the pain phenotype experienced during disc degeneration can be initiated solely by a sustained inflammatory profile. Markers indicative of nerve ingrowth into the IVD were also expressed suggesting a potential mechanism for the pain exhibited by animals. This rat injury model will allow for future study of the direct relationship between inflammation and pain in the degenerative environment.


title: METACLUSTERplus - an R package for probabilistic inference and visualization of context-specific transcriptional regulation of biosynthetic gene clusters

abstract: Fungi and plants reveal widespread occurrences of metabolic enzymes co-located on the chromosome, some already characterized as being biosynthetic pathways for specialized metabolites, such as terpenes synthesizing enzyme clusters in Lotus japonicus and Arabidopsis thaliana. These clusters display context-specific co-expression of clustered enzymes, indicating a shared transcriptional response in a spatial and condition specific manner, and co-regulation due to promoter binding by shared transcription factors may be one way to facilitate coordinated expression. To enhance our understanding of context-specific transcriptional gene cluster regulation, we redefine and augment this probabilistic framework, labelled METACLUSTERplus, integrating gene expression compendia, context-specific annotations, biosynthetic gene cluster definitions, as well as gene regulatory network architectures. Further, it provides a set of appealing and intuitive visualizations of inferred results for analysis and publication. METACLUSTERplus is available at https://github.com/mbanf/MetaclusterPlus.