脊髓小脑性共济失调35（SCA35）致病基因TGM6的转基因小鼠功能研究

In our previous study we have cloned TGM6, a new causative gene of autosomal dominant spinocerebellar ataxia type 35. Transglutaminase 6 protein is a member of the transglutaminase family whose most common function is to catalyze the formation of isopeptide linkages between the carboxamide group of protein bound glutamine residues and the ε-amino group of protein-bound lysine residue. TGs may contribute to the pathogenesis of many neurodegenerative disorders, including spinocerebellar ataxia，Alzheimer's disease, Parkinson's disease， and Huntington's disease, but the details of its mechanism is not clear. In this study, we intend to establish wild and mutant TGM6 transgenic mouse models to explore the distribution of endogenous TG6 and the characters of neurons that express it in normal controls, and to observe the distribution and pathogenesis alternatins of exogenous TG6 in transgentic models. Besides, we explore the role that TGM6 mutation plays in SCA from the overall level of experimental animals in several aspects，including ethology, histochemistry and pathophysiology. Our study can provide practical SCA models for future researches and theoretical clues for diagnosis, prevention and therapy of SCA.

TGM6是我们前期工作中克隆的脊髓小脑性共济失调35亚型（SCA35）致病基因。TGM6编码蛋白TG6是转谷氨酰胺酶（TG）家族成员之一，TGs主要催化谷氨酰胺残基的咪唑羧酰胺基团与赖氨酸残基的ε氨基基团反应，参与了SCA、阿尔兹海默病、帕金森病及亨廷顿病等多种神经退行性疾病的发病过程，但其具体发病机制仍不明确。本课题拟在前期工作的基础上，构建野生型和突变型TGM6转基因小鼠，观察其行为学变化，了解内源性TG6蛋白在中枢神经系统的分布及表达TG6神经元的性质，观察转基因小鼠外源性TG6蛋白的分布和表达变化及神经病理学改变。从行为学、组织化学和病理生理学等多角度在生物整体水平探讨TGM6突变在SCA发病机制中的作用，为SCA发病机制研究和药物研发提供有价值的动物模型，为今后此类疾病的诊断、预防和治疗提供理论依据。

前期我们克隆了一个新的脊髓小脑性共济失调35亚型(SCA35)致病基因- TGM6。TGM6参与了SCA等多种神经退行性疾病的发病过程,但其具体发病机制仍不明确。本课题在前期工作的基础上目成功地构建了TGM6wt、TGM6D327G 和TGM6L517W的转基因小鼠及TGM6-KO基因敲除小鼠模型，并进行外源基因和小鼠内源性基因敲除的基因型鉴定和表达鉴定，获得了良好的SCA基因工程小鼠模型；并对以上基因工程小鼠模型进行了行为学的观察，发现老年期Tgm6纯合敲除组小鼠运动能力或运动协调能力较野生型小鼠差；在内源性Tg6蛋白的分布研究中发现TG6在成年小鼠脑中广泛分布，尤其在间脑、脑干和小脑表达更为丰富，而皮层表达相对较少。大量TG6阳性的细胞表达在包括苍白球、底丘脑核、黑质、小脑、小脑深核和脊髓运动神经元在内的调节运动的关键脑区，另外，TG6表达在γ-氨基丁酸(GABA)能神经元而非神经胶质细胞。. 以上成果从行为学、组织化学等多角度在生物整体水平探讨 TGM6 突变在 SCA 发病机制中的作用，为 SCA 发病机制研究和药物研发提供有价值的动物模型，为今后此类疾病的诊断、预防和治疗提供理论依据。