MODY-X家系FOXM1基因G439V错义突变的致病机理研究

Maturity Onset Diabetes of the Young (MODY) is a monogenic diabetes. Accurate diagnosis of MODY is the key for precise treatment of MODY. Our previous results suggested that FOXM1 (G439V) is the pathogenic mutation in a MODY-X family, and the effect of this mutation on the proliferation of pancreatic beta-cells was decreased. However, the role and mechanism by which FOXM1 (G439V) causes MODY remain unclear. Therefore, we hypothesized that FOXM1 (G439V) mutation decreased the expression of CENP-A and PLK1. The decreased expression of PLK1 further reduced the amount of CENP-A on centromere, which ultimately inhibited the mitosis and proliferation of beta cells, resulting in diabetes. In this study, we aimed to establish three models of overexpression of FOXM1 (G439V) in beta cells, as well as FOXM1 (G439V) mutations in mouse and pancreatic beta-cells derived from the mutant mice, and then evaluate the effects of FOXM1 (G439V) mutation on the expression of CENP-A and PLK1, CENP-A deposition to centromere, and beta-cell proliferation and diabetic phenotype. We further studied the mechanism involved to rectify that the point mutation improved its transcriptional activity and enhanced beta-cell proliferation by using CRISPR/Cas9. Unraveling this mechanism will provide a novel strategy for precise treatment of this MODY subtype.

MODY是单基因突变引起青少年发病的成人型糖尿病，MODY的精确诊断是对其精准治疗的难题及关键。预实验发现FOXM1(G439V)是一个MODY-X家系致病性突变，且该突变促胰岛β细胞增殖作用下降，然而其在该病中的作用及机制尚不清楚。由此我们假设FOXM1(G439V)突变使其靶基因CENP-A、PLK1表达下降，PLK1促CENP-A富集在着丝粒作用下降，CENP-A在着丝粒上沉积进一步减少，β细胞有丝分裂及增殖减少而诱发糖尿病。本项目拟在过表达FOXM1(G439V)细胞模型、FOXM1(G439V)点突变小鼠及该点突变小鼠胰岛β细胞模型，观察点突变对CENP-A与PLK1表达、CENP-A在着丝粒上沉积、细胞增殖及糖尿病表型的影响，通过CRISPR/Cas9基因编辑研究对该点突变进行修复后改善其转录活性进而改善β细胞增殖的分子机制。阐明该机制，将为该类型MODY的精准治疗提供新思路。

单基因糖尿病是由在胰岛β细胞发育、功能或胰岛素信号通路中起关键作用的单个基因突变导致的一种特殊类型糖尿病，而青少年发病的成人型糖尿病（MODY）作为一种单基因糖尿病在全世界范围内已发现14种MODY亚型。在中国，MODY研究较为滞后，绝大部分并非已知的MODY致病基因。MODY是一组高度异质性的单基因遗传病，其临床疾病特征也具有高度异质性，且对降糖药物的反应具有明显差异，因此，MODY的精确诊断与精准治疗，对于改善血糖、提高生活质量，并且对其家庭成员的遗传咨询具有重要意义。本项目围绕单基因糖尿病的致病基因、发病机制与精准治疗进行多维度研究，目前共计发表论文4篇。本项目主要实验结果有⑴FOXM1为MODY致病基因，阐明了FOXM1 (G439V)突变使其靶基因CENP-A、PLK1表达下降，PLK1促CENP-A富集在着丝粒作用下降，CENP-A在着丝粒上沉积进一步减少，β细胞有丝分裂及增殖减少而诱发糖尿病；⑵MODY2型糖尿病患者除妊娠期外可以通过饮食、锻炼控制血糖，而无需使用降糖药物；⑶MODY12型糖尿病对磺脲类药物较敏感；⑷对单基因糖尿病的发病年龄、临床特征、遗传特征、精准治疗等进行系统综述；⑸IRS1（c.2137C>T，p.His387Tyr）错义突变与早发2型糖尿病密切相关；⑹ATP7B组合突变使铜离子沉积于胰腺而引起β细胞凋亡而诱发糖尿病。综上，单基因遗传病的精确诊断与精准治疗至关重要。