Division of Molecular Medicine, Leeds Institute of Medical Research, University of Leeds, United Kingdom.
Institute of Biological, Environmental & Rural Sciences, Aberystwyth University, United Kingdom.
Mol Vis. 2022 May 17;28:57-69. eCollection 2022.
To investigate the molecular basis of recessively inherited congenital cataract, microcornea, and corneal opacification with or without coloboma and microphthalmia in two consanguineous families.
Conventional autozygosity mapping was performed using single nucleotide polymorphism (SNP) microarrays. Whole-exome sequencing was completed on genomic DNA from one affected member of each family. Exome sequence data were also used for homozygosity mapping and copy number variation analysis. PCR and Sanger sequencing were used to confirm the identification of mutations and to screen further patients. Evolutionary conservation of protein sequences was assessed using CLUSTALW, and protein structures were modeled using PyMol.
In family MEP68, a novel homozygous nucleotide substitution in was found, c.547G>C, that converts the evolutionarily conserved aspartic acid residue at the 183 amino acid in the protein to a histidine, p.(Asp183His). This residue mapped to the third helix of the DNA-binding homeobox domain in SIX6, which interacts with the major groove of double-stranded DNA. This interaction is likely to be disrupted by the mutation. In family F1332, a novel homozygous 1034 bp deletion that encompasses the first exon of was identified, chr14:g.60975890_60976923del. Both mutations segregated with the disease phenotype as expected for a recessive condition and were absent from publicly available variant databases.
Our findings expand the mutation spectrum in this form of inherited eye disease and confirm that homozygous human mutations cause a developmental spectrum of ocular phenotypes that includes not only the previously described features of microphthalmia, coloboma, and congenital cataract but also corneal abnormalities.
研究两个近亲家族中隐性遗传性先天性白内障、小角膜、角膜混浊伴或不伴视网膜裂孔和小眼球的分子基础。
使用单核苷酸多态性（SNP）微阵列进行常规自交分析。对每个家族的一位受影响成员的基因组 DNA 进行全外显子测序。外显子序列数据也用于纯合子作图和拷贝数变异分析。PCR 和 Sanger 测序用于确认突变的鉴定，并进一步筛选患者。使用 CLUSTALW 评估蛋白质序列的进化保守性，使用 PyMol 构建蛋白质结构模型。
在 MEP68 家族中，发现了一个新的纯合核苷酸替换，c.547G>C，导致蛋白质中第 183 个氨基酸的保守天冬氨酸残基突变为组氨酸，p.(Asp183His)。该残基位于 SIX6 的 DNA 结合同源盒结构域的第三个螺旋中，与双链 DNA 的大沟相互作用。这种相互作用可能被突变破坏。在 F1332 家族中，发现了一个新的纯合 1034 bp 缺失，包含 基因的第一个外显子，chr14:g.60975890_60976923del。这两种突变与疾病表型一起遗传，符合隐性条件，并且不存在于公共可用的变异数据库中。
我们的发现扩展了这种遗传性眼病形式的突变谱，并证实纯合人 突变导致眼部表型的发育谱，不仅包括以前描述的小眼球、视网膜裂孔和先天性白内障的特征，还包括角膜异常。
