Research On The Function And The Underlying Mechanism Of SPG42Causative Gene SLC33A1

Hereditary spastic paraplegia is a group of clinically and genetically heterogeneous neurodegenerative disorders. The key symptom are progressive spasticity, weakness of lower limbs. Neuropathological analysis reveals that the diseases have retrograde axonal degeneration of corticospinal tracts and posterior spinal tracts, especially the thoracic segments.To date,61HSP loci and40spastic-paraplegia genes have been identified. Among the detected causative genes, the SPG42causative gene SLC33A1is identified by our lab through linkage and mutation analysis of a pedigree of HSP with autosomal-dominant inheritance. All the patients carried the p.S113R (c.339T>G) missense mutation in SLC33A1gene. Although we performed prenatal diagnosis through linkage and mutation analysis on children of the patients to find out that they are not the mutation carrier, additional work is need to elucidate the molecular mechanism of the protein and to determine the relationship between this protein and the disease development. In these studies, we constructed the cell models which expressed SLC33A1with different levels to find out the functions of SLC33A1and then detect the possible mechanism how the S113R missense mutation implicate on HSP.We constructed the HEK293cell lines which SLC33A1expression was stably over-expressed and low-expressed successfully. And we derived mouse embryo fibroblasts from the mice which have Slc33al missense mutation. For the phenotype research, we found out that over-expression of SLC33A1can promote the proliferation and the survival ability of cells and prevent autophagy. When SLC33A1was low-expressed, the proliferation was slow down and the survival ability of cells was decreased and autophagy was increased. Otherwise the missense mutated SLC33A1only decrease cell viability without have effects on apoptosis and autophagy. Then we determined that SLC33A1can promote proliferation through activating the Wnt/β-catenin signaling. We also observed that missense mutated SLC33A1up-regulating the levels of BMPR1A by inhibiting its degradation in lysosome, then activated the BMP signaling abnormally and changed the expression of the target genes.In additional, we reprogrammed the mouse embryonic fibroblasts cells of mouse model with Slc33al missense mutation to iPSCs. The iPSCs which have a missense mutation of Slc33al offer unprecedented cell models to investigate the functions in embryonic development and disease mechanisms.In conclusion, SLC33A1plays an important role in proliferation, survival ability and autophagy of cells. P.S113R (c.339T>G) missense mutation in SLC33A1gene up-regulates the BMP signal through inhibiting the degradation of BMPR1A in lysosomes. We also induced iPSCs from mouse embryonic fibroblasts cells carrying p.S113R(c.339T>G) missense mutation. All these results provide clues and offer unprecedented cell models for further study of the disease progress which caused by p.S113R (c.339T>G) missense mutation in SLC33A1gene.