中国家系新发AQP2突变致遗传性肾性尿崩症（HNDI）的分子发病机制及药物干预作用的体内外研究

Hereditary nephrogenic diabetes insipidus(HNDI) is a disorder of water metabolism resulting from rare congenital genetic deficiency, which can result in severe hypernatrium and recurrent dehydration. AVP-AVPR2-AQP2 axis is the key signal pathway regulating urinary concentration. AQP2 is the main pathogenicity gene for HNDI. Now the treatments for HNDI are limited and not effective. Recent studies demonstrate that AQP2 mutations may result in mutant AQP2 retention in the ER and rapid degradation, also can affect amino acid phosphorylation at some specific sites of AQP2 and result in defective trafficking, which are responsible for HNDI(Autosome Recessive and Autosome Dominant). Mature molecular pathogenic mechanisms for AQP2 mutations are still to be clarified, especially novel mutation. We found two novel missense mutations(L116R, G165D) in two Chinese families respectively and the same base deletion(E4-3delC) mutaition in other two Chinese families, and the deletion is predicted to result in splicing mutation, causing AD HNDI. Molecular mechanisms for these novel mutations are still unknown. There are no animal models for HNDI in China now. We decide to culture MDCK cells stablely transferred with AQP2 vectors and build transgenic mice models. we plan to utilize them to explore the molecular mechanisms of AQP2 mutations in vitro and in vivo，detecting the expression of AQP2 mRNA and protein, but also the phosphorylation and celluar trafficking of AQP2. Drugs effects will also be observated. We aim to clarify the molecular mechanisms of these three novel AQP2 mutations and provide MDCK cells and transgenic mice models for drug screening.

遗传性肾性尿崩症（HNDI）是罕见的先天性遗传缺陷导致的水代谢紊乱性疾病，可造成严重的高钠血症和反复的脱水状态。AQP2是引起HNDI的主要致病基因，针对AQP2突变致HNDI的治疗手段有限。研究证明AQP2突变导致AQP2蛋白滞留内质网而被快速降解、AQP2特异位点磷酸化异常和错误转运在HNDI的发生中起关键作用，但部分AQP2突变的发病机制尚不清楚；国内尚无HNDI相关动物模型的报道。我们前期发现2个HNDI中国家系分别存在2种新发现的AQP2错义突变（L116R、G165D）,发病机制尚不清楚；2个HNDI中国人家系同时存在1种新发现的AQP2碱基缺失突变(E4-3delC) ，呈常染色体显性遗传，发病机制不明，推测可能导致剪接异常，目前尚无剪接突变致常染色体显性HNDI的相关报道。本项目拟采用动物及细胞分子生物学技术，体内外研究突变型AQP2的mRNA和蛋白表达水平、蛋白磷酸化修饰、胞内转运的分子机制。

遗传性肾性尿崩症（HNDI）是罕见的先天性遗传缺陷导致的水代谢紊乱性疾病，可造成严重的高钠血症和反复的脱水状态。AQP2是引起HNDI的主要致病基因，针对AQP2突变致HNDI的治疗手段有限。研究证明AQP2突变导致AQP2蛋白滞留内质网而被快速降解、AQP2特异位点磷酸化异常和错误转运在HNDI的发生中起关键作用，但部分AQP2突变的发病机制尚不清楚；国内尚无HNDI相关动物模型的报道。我们发现HNDI中国家系新发AQP2错义突变（G215S）,发病机制尚不清楚，本项目采用动物及细胞分子生物学技术，体内外研究突变型AQP2的mRNA和蛋白表达水平、蛋白磷酸化修饰、胞内转运的分子机制，结果表明：在MDCK细胞系突变型AQP2-G215S蛋白可以表达，但是存在转运异常，滞留于内质网，影响AQP2转运至细胞膜发挥功能；在AQP2-G215S转基因小鼠，小鼠的尿量、尿渗透压与野生型小鼠无明显差异，未发现疾病表型，暗示可能存在物种差异，人源化疾病模型更加有助于疾病机制的深入研究。