线粒体分裂和融合机制障碍在SCA3/MJD发病机制中的作用

PD-associated gene, PINK1, has been implicated in controlling mitochondrial morphology though increases fission and inhibits fusion. The latest evidences showed that down-expression of PINK1 caused mitochondrial elongation and deteriorate neurodegeneration of PD transgenic flies. Interestingly, in previous work we have shown that knockdown of pink1 by RNA interference (RNAi) significantly suppressed phenotype of Drosophila model of SCA3/MJD, Conversely, overexpression of PINK1 led to an enhanced neurodegenerative phenotype. In this study, we will utilize transgenic flies that mitochondrials of motor neuron were labeled by GFP fluorescence to definite that relationship between PINK1 knockdown significantly inhibits phenotype of SCA3/MJD transgenic flies and inhibited fission or increased fusion, with different methods including RNA intervention, Western blotting and Real Time PCR. It is important to determinate whether excess mitochondrial fission or inhibited fusion contributes to the Pathogenesis of SCA3/MJD. We will further explore the biological role of mitochondrial dynamic in clinical character such as anticipation and late -onset in SCA3/MJD family. These results will provide strong support for studying Pathogenesis of SCA3/MJD.

PINK1是一种帕金森病相关蛋白，具有促进线粒体分裂、抑制线粒体融合的功能，最近的研究证实，PINK1表达下调可显著加重帕金森病转基因果蝇的神经元变性、死亡。然而，我们在前期研究中却发现，PINK1表达下调显著抑制了SCA3/MJD转基因果蝇的神经变性，而PINK1过表达的结果却完全相反。在本课题中，我们将进一步利用线粒体被GFP荧光标记的转基因果蝇，通过siRNA、免疫印迹以及qRT-PCR等方法，研究PINK1表达下调显著抑制SCA3/MJD转基因果蝇神经变性是否与其抑制线粒体分裂或促进线粒体融合有关，明确SCA3/MJD致病蛋白ataxin-3突变是否导致了线粒体过度分裂或线粒体融合功能障碍，进一步探讨SCA3/MJD疾病遗传早现和迟发性现象与线粒体分裂和融合机制障碍的关系，阐述线粒体分裂和融合机制障碍在SCA3/MJD发病机制中的作用，为研究SCA3/MJD发病机制提供理论依据。

线粒体分裂和融合的动态平衡失调导致的线粒体功能障碍与神经退行性疾病神经元变性密切相关，然而其确切关系仍不清楚。PINK1近来被证实通过Parkin促进线粒体分裂，抑制线粒体融合。在以前的研究中我们发现，Pink1表达下调抑制了SCA3/MJD转基因果蝇眼睛神经变性，但在本研究中我们发现, SCA3/MJD转基因果蝇肌肉线粒体较正常果蝇显著融合,线粒体功能明显受损；而过表达与线粒体分裂相关的PINK1或促线粒体分裂基因drp1减少了SCA3/MJD转基因果蝇翅膀异常率，显著提高了果蝇的飞行能力。研究结果表明，SCA3/MJD疾病或许存在过度线粒体融合或线粒体分裂障碍，但不同组织结果并不一致，提示存在组织特异性。