Molecular cloning and functional analysis of gene responsible for multiple ocular defect of cattle

牛的多发性眼部缺陷(MOD)是一种常染色体隐性遗传性疾病，以晶状体发育不良、视网膜脱离、玻璃体动脉持续存在和小眼炎为特征。将MOD基因定位在牛18号染色体的近端区域，通过单倍型分析进一步将该基因定位在牛18号染色体上1.1 Mb的区间内，并测定了该区域内所有基因的核苷酸序列。对患病动物和正常动物的这些基因的核苷酸序列进行比较发现，在WFDCL基因的第二外显子上有一个核苷酸插入，这导致了一个移码突变。WFDCL是一种含有WAP型四个二硫键核心区的小分子分泌型蛋白。通过免疫组织化学染色和原位杂交，观察到Wfdc1在胚胎和成年小鼠眼的晶状体、视网膜和视神经中特异表达。虽然WFDCL在哺乳动物发育中的确切功能尚不清楚，但目前的研究结果表明，WFDCL的这种突变导致了多种眼缺陷，并且该基因在胚胎和成人眼中特异表达，表明WFDCL在哺乳动物眼发育中发挥着重要作用。这是第一份提供WFDCL参与特定哺乳动物发育过程的直接证据的报告。

Multiple ocular defects (MOD) in cattle is an autosomal recessive hereditary disorder characterized by dysplasia of the lens, retinal detachment, persistence of the hyaloid artery, and microphthalmia. The locus responsible for MOD was mapped to the proximal region of bovine chromosome 18. We further refined the localization of the MOD locus to within a 1.1 Mb interval on bovine chromosome 18 by haplotype analysis and determined the nucleotide sequences of all genes in this region. A comparison of the nucleotide sequences of these genes between affected and normal animals revealed a one-nucleotide insertion in exon 2 of the WFDCl gene, which resulted in a frame shift mutation. WFDCl is a small secretory protein containing a WAP-type four disulfide core domain. Specific expression of Wfdcl was observed in the lens, retina, and optic nerves of embryonic and adult mouse eyes by immunohistochemical staining and in situ hybridization. Although the exact function of WFDCl in mammalian development remains unknown, the present findings showing that this mutation in WFDCl resulted in multiple eye defects and that the gene is specifically expressed in embryonic and adult eyes demonstrated the essential role of WFDCl in mammalian eye development. This is the first report providing direct evidence for the involvement of WFDCl in a particular process of mammalian development.