Abstract：
Congenital cataracts are the leading cause of irreversible visual disability in children, and genetic factors play an important role in their development. In this study, targeted exome sequencing revealed a novel single-base deletional mutation of MIP (c.301delG; p.Ala101Profs*16) segregated with congenital punctate cataract in a Chinese family. The hydrophobic properties, and secondary and tertiary structures for truncated MIP were predicted to affect the function of protein by bioinformatics analysis. When MIP-WT and MIP-Ala101fs expression constructs were singly transfected into HeLa cells, it was found that the mRNA level showed no significant difference, while the protein level of the mutant was remarkably reduced compared to that of the wild-type MIP. Immunofluorescence images showed that the MIP-WT was principally localized to the plasma membrane, whereas the MIP-Ala101fs protein was aberrantly trapped in the cytoplasm. Furthermore, the cell-to-cell adhesion capability and the cell-to-cell communication property were both significantly reduced for MIP-Ala101fs compared to the MIP-WT (all *p < 0.05). This is the first report of the c.301delG mutation in the MIP gene associated with autosomal dominant congenital cataracts. We propose that the cataract is caused by the decreased protein expression and reduced cell-to-cell adhesion by the mutant MIP. The impaired trafficking or instability of the mutant protein, as well as compromised intercellular communication is probably a concurrent result of the mutation. The results expand the genetic and phenotypic spectra of MIP and help to better understand the molecular basis of congenital cataracts.
摘要：
先天性白内障是导致儿童不可逆视力障碍的主要原因，遗传因素在其发展中起着重要作用。在这项研究中,靶向外显子组测序揭示了一个新的单碱基缺失突变的MIP(c.301delG;p.Ala101Profs*16),在一个中国家庭中与先天性点状白内障分离.疏水性，通过生物信息学分析，预测截短MIP的二级和三级结构会影响蛋白质的功能。当将MIP-WT和MIP-Ala101fs表达构建体单独转染到HeLa细胞中时，发现mRNA水平没有显着差异，与野生型MIP相比，突变体的蛋白质水平显着降低。免疫荧光图像显示MIP-WT主要位于质膜，而MIP-Ala101fs蛋白被异常捕获在细胞质中。此外，与MIP-WT相比，MIP-Ala101fs的细胞间粘附能力和细胞间通讯特性均显着降低（均*p<0.05）。这是与常染色体显性遗传先天性白内障相关的MIP基因c.301delG突变的首次报道。我们认为白内障是由突变MIP导致的蛋白质表达减少和细胞间粘附减少引起的。突变蛋白的运输受损或不稳定，以及受损的细胞间通讯可能是突变的并发结果。结果扩展了MIP的遗传和表型谱，并有助于更好地了解先天性白内障的分子基础。
