To Study The Abnormal Phenotype In SCA Drosophila Model Caused By Gene X

Spinocerebellar ataxia (SCA, spinocerebellar ataxia) is a class of inherited neurodegenerative diseases. Currently, more than30SCA subtypes have been found (DRPLA, SCA1-8,10-23,25-31). The most characteristic genetic defect in SCA is amplified trinucleotide CAG repeat encoding polyglutamine, which would result in the formation of nuclear inclusion. The primary clinical features of SCA refer to the lesion in spinal cord and cerebellum, aslo have effect on spinal nerves, cranial nerves, sympathetic nerves.A new SCA causative gene X was identified by our cooperator in a autosomal recessive pedigree of SCA by exome-sequency and genetic pedigree analysis (As the research has not been published, the gene temporarily be replaced with X, for the same reason M, A, B, C are also substitutes for relative genes). Through literature search, we found that X is a novel ubiquitin-like protein activating enzyme (E1), which activates ubiquitin-like protein M, other components of this system include A gene which encodes a conjugating enzyme (E2) of M, and B gene which encodes a ligase (E3) of M. A study in caenorhabditis elegans, researchers found M cascade is negatively regulated IRE1-mediated (inositol-requiring protein-1, IRE1) unfold protein reaction, and consequently effect on the reproduction, development and resistance of environmental stress of caenorhabditis elegans. Another study in X knockout mice found that embryos with X knockout die in utero due to severe anemia, futher study found that the X and M cascade involved in the erythroid differentiation and the induction of blood cell death of mice.Purpose:The function of X gene and the participant of X in the pathogenesis of SCA require futher study. Firstly, we have established a new SCA drosophila model; secondly, we have performed functional studies in the model. The result provide theoretical basis for the involvement of X gene in the pathogenesis of SCA.Methods:We use UAS-GAL4system to induce the knockdown of gene X and other genes in the M system, and observe the abnormal phenotype.Results:1) we found a stable phenotype which can be described as vertically stretch out of one side wing or both side of wing in X gene knockdown drosophila. The ratio of the wing phenotype reaches33.5%in25℃. Meanwhile, obvious decrease in flight and climbling ability of X gene knockdown drosophila was observed;2) paraffin sections were performed in the thorax of the drosophila (3days after eclosion) with X gene knockdown. The result showed no apparent abnormality in the morphology of muscle tissue;3) we performed dissection and imaging of active zones in the neuromuscular junction of the third instar larvae with X gene knockdown, result shows decrease in the number of neuromuscular junctions on muscle4and muscle13-12of ventral longitudinal muscle;4) drosophila with M, A gene knockdown shows same abnormal wing phenotype, the ratio of the wing phenotype reaches71.3%and37.8%respectively in25℃.Conclusion:The drosophila model with X gene knockdown can mimic the phenotype of this type of SCA, and knockdown of M and A, which is the components of the M casecade, also showed same abnormal wing phenotype. The result revealed that M casecade play important role in the pathology of SCA.