Identification of the mechanism underlying the genetic modes of species-specific phenotypic differences

尽管人类和小鼠中由透镜纤维（Mip）突变的主要内在蛋白引起的白内障形成具有显性遗传模式，但大鼠模型KFRS 4（其在Mip中具有截断蛋白的5-bp插入）中的白内障发生是隐性遗传的。为了证实人类/小鼠和大鼠之间白内障发生的遗传模式的种属特异性差异，我们产生了新的小鼠和大鼠Mip突变体，并分析了它们的透镜表型。首先，我们通过使用CRISPR/Cas9进行基因组编辑，创建了具有与KFRS 4大鼠相似突变的小鼠突变体。杂合子Mip突变体表现出严重的透镜混浊。接下来，我们筛选了ENU诱变文库中的新型大鼠Mip突变，并鉴定了位于与人类患者中已知突变位点类似的位点的两个错义突变。在晶状体的表型分析中，在Mip突变杂合子大鼠中未观察到透镜混浊。

Although cataract formation caused by major intrinsic protein of lens fiber (Mip) mutations in humans and mice has a dominant mode of inheritance, cataractogenesis in a rat model KFRS4, which has a 5-bp insertion in Mip that truncates the protein, is recessively inherited. To confirm the species-specific differences in the genetic mode of cataractogenesis between humans/mice and rats, we generated new mouse and rat Mip mutants and analyzed their lens phenotypes. First, we created mouse mutants with mutations similar to that in the KFRS4 rat by performing genome editing using CRISPR/Cas9. The heterozygous Mip mutants exhibited severe lens opacity. Next, we screened an ENU mutagenesis library for novel rat Mip mutations and identified two missense mutations located at sites analogous to known mutation sites in human patients. In phenotypic analyses of the lenses, no lens opacity was observed in the rats heterozygous for either Mip mutation.