GLIS3基因突变诱发MODY-X家系高血糖表型的致病作用和机理研究

基因诊断决定MODY分型与精准治疗。80%以上中国MODY系未知MODY-X基因突变所致。GLIS3位于胰岛β细胞转录因子调控网络上游级层，调控胰腺分化、发育和β细胞功能；调节MODY基因转录。二代测序筛查78个MODY家系29个单基因糖尿病靶基因，发现GLIS3-Q744H新突变（小鼠Q749H）与一家族4代高血糖表型呈遗传-共分离。研究显示，Q744H突变体转录活性和胰岛素分泌皆显著下降；3D结构改变严重影响功能。本项目结合前期研究结果，通过构建胰腺条件性mGLIS3-Q749H点突变小鼠模型，研究：1）突变对胰腺和胰岛β细胞分化、发育和功能，对胰岛素基因转录与表达的影响；2）突变导致糖尿病信号通路及相关基因转录与表达的改变；3）GLIS3过表达对于Q749H突变小鼠糖尿病表型的逆转、缓解作用。从分子、细胞和整体水平阐明GLIS3-Q749H突变导致MODY型糖尿病发生的机理。

Genetic diagnosis determines the MODY subtype and its precision treatment. More than 80% of MODY patients in China are caused by unknown MODY genes i.e. MODY-X. GLIS3, located in the upstream hierarchy in the transcriptional factor network of pancreatic β cells, regulates the pancreatic differentiation and development, the function of β cells as well as the transcription of MODY genes. In the preliminary study, twenty-nine target genes of monogenic diabetes were screened by next-generation sequencing (NGS) in 78 classic MODY families. A novel mutation Q744H which corresponds to Q749H in GLIS3 gene in mouse was identified in a four-generation family and co-segregated with hyperglycemic phenotypes. We observed that both the transcriptional activity and glucose-stimulated insulin secretion (GSIS) of Q744H mutant were significantly reduced, and the change of three-dimensional (3D) structure in mutant protein severely affected its functions. Based on earlier clinical genotype-phenotype studies, we will generate Knock-In mouse model of pancreatic conditional mGLIS3-Q749H point mutation, and investigate the biological behavior of this mutant in the following aspects: 1) its effect on the development, differentiation and function of pancreas and islet β cells, as well as the transcription and expression of insulin genes; 2) to explore the differentially expressed genes related to diabetes signaling pathways caused by the mutation; 3) how the overexpression of GLIS3 in conditional point mutation mouse will reverse or relieve diabetic phenotypes. The mechanism that GLIS3-Q749H mutation leads to MODY will be elucidated in molecular, cellular and in vivo level.