基于PolyA-NOTCH2NLC毒性蛋白的眼咽远端型肌病3型致病机制研究

眼咽远端型肌病(OPDM)是一种成年早期发病的遗传性肌肉病。课题组研究发现NOTCH2NLC基因5’非编码区GGC高重复次数(约200次)扩增是OPDM3型的致病变异，然而该基因变异导致OPDM3的机制尚不清楚。课题组前期研究提示该基因变异可能通过RAN非经典启动子翻译机制产生一种新的含多聚丙氨酸(PloyA-NOTCH2NLC)的毒性蛋白，该蛋白作用于特定靶蛋白而造成肌细胞损伤，进而导致包涵体形成和细胞变性。本课题将在患者活检样本、质粒转染细胞和转基因动物模型中，运用病理学、分子生物学、转录组学和蛋白组学等方法，探索NOTCH2NLC 基因5’非编码区GGC高重复次数扩增产生PloyA-NOTCH2NLC的分子机制和调控机制，以及该蛋白与相作用靶蛋白介导的肌细胞毒性及其分子机制。该研究将为OPDM3可能的治疗靶点提供理论依据，也为其他高GC重复扩增疾病的致病机制提供研究思路。

Oculopharyngodistal myopathy (OPDM) is an inherited myopathy with early-adult onset. Our previous studies have identified high number of GGC repeat expansion (about 200 repeats) in the 5'-untranslated region (5’UTR) of the NOTCH2NLC gene as the third genetic cause of OPDM (OPDM3), following the report of trinucleotide repeat expansion in the LRP12 and GIPC1 gene which were the first and second causative gene of OPDM, respectively. Based on our previous data and literature, we proposed that trinucleotide repeat expansion of NOTCH2NLC gene may be translated into a toxic protein, named as PolyA-NOTCH2NLC, through a mode of non-ATG start codon associated with repeat expansion, which play an important role in the pathogenesis of OPDM3. Thus, a pathogenesis hypothesis of the disease is suggested: trinucleotide repeated expansion in NOTCH2NLC might translate into a toxic protein PolyA-NOTCH2NLC, and this protein might involve a specific target protein or molecular pathway, finally cause intramuscular inclusion body formation and degeneration of muscle cells. In order to validate this hypothesis, we will construct transgenic cells and animal models with NOTCH2NLC GGC repeat expansion, and employ comprehensive laboratory techniques including pathology, molecular biology, transcriptome and proteomics in this study. We aim to explore the molecular mechanism of PolyA-NOTCH2NLC translation associated with high number of GGC repeat expansions in NOTCH2NLC; the target proteins that interact with PolyA-NOTCH2NLC; and the pathogenic pathways of PolyA-NOTCH2NLC cytotoxicity. The study might reveal the pathogenic mechanism of OPDM3 and provide possible therapeutic targets for the disease. The study also could provide some hints for other diseases associated with trinucleotide repeat expansions with high GC content.