Generation of Wolfram syndrome mice, aiming at development of new therapeutics for diabetes through preserving pancreatic beta cells

Wolfram综合征是一种常染色体隐性遗传疾病，与青少年发病的糖尿病、视神经萎缩、感音神经性耳聋和尿崩症有关。我们确定，采用定位克隆，一个基因负责这种疾病，并指定它WFS 1。我们还发现WFS 1蛋白定位于ER膜。此外，WFS 1与酵母Hrd 3 p有一些序列相似性，后者参与错误折叠蛋白质的ER相关降解。因此，虽然WFS 1蛋白似乎在ER应激反应中发挥作用，但其确切功能仍有待澄清。为了阐明这种新蛋白的功能和Wolfram综合征的病理生理学，我们产生了缺乏WFS 1基因的小鼠（WFS 1-KO）。雄性WFS 1-KO小鼠的血糖水平在约12周时开始升高，并且在24周时显著高于野生型小鼠的血糖水平（267±33 vs 146±34 mg/dl）。这与胰岛β细胞的损失有关; WFS 1-KO小鼠的全胰腺胰岛素含量比野生型小鼠低30倍（11±4 vs 287±34 ng/mg胰腺）。使用抗WFS 1蛋白抗体的胰腺免疫组织化学分析显示，WFS 1蛋白在外分泌组织中不存在，但在内分泌β细胞中强烈表达。WFS 1蛋白在胰高血糖素阳性细胞中不表达，大多数生长抑素和胰多肽阳性细胞缺乏WFS 1免疫反应性。在WFS 1-KO小鼠中，β细胞数量随着年龄的增长而下降，而α细胞略有增加，并分散在整个胰岛中。这些结果强烈表明，WFS 1蛋白在β细胞的存活和/或再生中起关键作用，并且胰岛β细胞的进行性丧失是这种疾病中糖尿病的主要原因。

Wolfram syndrome is an autosomal recessive disorder associated with juvenile onset diabetes mellitus, optic atrophy, sensorineural deafness and diabetes insipidus. We identified, employing positional cloning, a gene responsible for this disorder and designated it WFS1. We also showed WFS1 protein to be localized in the ER membrane. In addition, WFS1 shares some sequence similarity with yeast Hrd3p, which is involved in ER-associated degradation of malfolded proteins. Thus, though WFS1 protein appears to play a role in the ER-stress response, its precise function remains to be clarified. To elucidate the functions of this novel protein and the pathophysiology of Wolfram syndrome, we have generated mice lacking the WFS1 gene (WFS1-KO). WFS1-KO mice are normal in appearance, growth and fertility Blood glucose levels in male WFS1-KO mice start to rise at around 12 weeks and are significantly higher than those of wild-type mice at 24 weeks (267±33 vs 146±34 mg/dl). This is associated with loss of islet β cells; whole pancreatic insulin content in WFS1-KO mice was 30-times lower than that in wild-type mice (11±4 vs 287±34 ng/mg pancreas). Immunohistochemical analysis of the pancreas using an anti-WFS1 protein antibody revealed that WFS1 protein is absent from exocrine tissue, but is strongly expressed in endocrine β cells. WFS1 protein is not expressed in glucagon-positive cells and the majority of somatostatin-, and pancreatic polypeptide-positive cells are devoid of WFS1 immunoreactivity. In WFS1-KO mice, β cell number fell with age, while a cells were somewhat increased and were scattered throughout the islet. These results strongly suggest WFS1 protein to play a critical role in survival and/or regeneration of β cells and progressive loss of islet β cells to be the major cause of diabetes in this disorder.