Investigation Of SNX14 Mutations In The Pathogenesis Of Cerebellar Atrophy

The hereditary cerebellar ataxias are a heterogeneous group of disorders characterized by ataxia,coarse facial features,atrophy or hypoplasia of the cerebellum and neurodegeneration.A common hallmark of the cerebellar ataxias is a progressive cerebellar neurodegeneration due to Purkinje cell loss.The disease include the spinocerebellar ataxias,Friedreich ataxia and ataxia telangiectasia,affect about 8.9 per 100,000 people worldwide.In addition to the dominant trinucleotide-repeat disorders that lead to toxic accumulation of unfolded protein,the recessive forms of disease are associated with loss-of-functionmutations and early-onset presentations.Mutations in the gene SNX14,encoding for a sorting nexin,have been found to cause antosomal recessive spinocerebellar ataxia and purkinje cell loss,however,the underlying molecular mechanism remains elusive.SNX14 belongs to a large family of sorting nexin proteins and plays a vital role in cellular trafficking,signaling and development.To determine the roles of SNX14 in cerebellum and purkinje cells,we took advantage of a Snx14 conditional knockout mouse model to delete SNX14 in brain and purkinje cell specifically.We found that Nestin-cre;Snx14 flox/flpx mice have grossly normal brain anatomy,but exhibit severe motor defects and substantial loss of purkinje cells in the cerebellum as disease progresses.Meanwhile,Pcp2-cre;Snx14flox/flox mice displayed the similar behavioral defects and purkinje death,which suggests that the neurodegeneration in Nestin-cre;Snx14flox/flox mice is caused by purkinje cell-autonomous death.In addition,the purkinje cells of Nestin-cre;Snx14flox/flox mice showed higher electron density and smaller size of mitochondria under transmission electron microscope.To explain the mechanism of Purkinje cell death,we identified multiple SNX 14 interaction proteins using proteomics for considering that SNX14 may functions as a protein sorting hub.Several of them have been reported to be asscoaited with SCAs,such as AMPD2,CTND2 and VPP1.Moreover,we found that SNX 14 colocalized with lysosomal marker Lamp2 in Hela cells.In summary,we improved that SNX14 defect make a direct contribution to purkinje cells cell-autonomous death that lead to cerebellar ataxias.Moreover,we identified several SNX14 binding proteins that may provide insights to discern the underlying molecular mechanisms.And we also give a mice model for therapeutic drugs research of the disease.