Although spastic paraplegia type 7 is considered to be a recessive disease, some clinical observations also argue for a detrimental effect of a variant in SPG7 in the heterozygous state. Thus, the presence of a single mutated variant of the SPG7 gene could be a risk factor for the development of neurological diseases. This has important implications for genetic counseling of patients and for the understanding of the function of the SPG7 protein and the mechanisms of disease development. To date there have been no studies to specifically explore the pathogenic role of single heterozygous variants in the SPG7 gene.~The aim of this project is to fully characterize different models expressing single heterozygous SPG7 mutations in order to detect phenotypical, biological or functional alterations. In particular, the investigators will conduct analysis on fibroblasts from symptomatic patients with mutations in the SPG7 gene (homozygous, compound heterozygous or single heterozygous), and controls. Cellular models will be particularly useful in order to study an alteration in calcium homeostasis and in the response to ER stressors. In parallel, studies will be performed using the genetic animal model of Drosophila melanogaster.
Paraplegin, encoded by the SPG7 gene, is an ATP-dependent mAAA protease located in the inner mitochondrial membrane. Its function is not fully understood. Mutations in the SPG7 gene are responsible for spastic paraplegia type 7. Although spastic paraplegia type 7 is considered to be a recessive disease, some clinical observations also point to a detrimental effect of a variant in SPG7 in the heterozygous state. Thus, the presence of a single mutated variant of the SPG7 gene could be a risk factor for the development of neurological diseases. This has important implications for genetic counseling of patients and for the understanding of the function of the SPG7 protein and the mechanisms of disease development.