Objective: To investigate the possibility of the visual system homeobox 1 (VSX1) gene as a candidate susceptibility gene for Chinese patients with sporadic keratoconus, and to identify sequence variants of the VSX1 gene in such patients. Methods: Cross-sectional study. Genomic DNA was extracted from the leukocytes in the peripheral venous blood of 50 patients with sporadic keratoconus and 50 control subjects without this ocular disorder. Five exons and the intron-exon splicing of the VSX1 gene were amplified by polymerase chain reaction (PCR). The PCR products were directly sequenced and compared to the GeneBank database to find mutations. Bioinformatics analysis was done to predict the influence of these mutations on proteins. Results: One novel missense heterozygous mutation (p.R131P) was found in exon 1 of the VSX1 gene in one keratoconus patient. Another heterozygous mutation (p.G160V) in exon 2 was found in two keratoconus patients. These mutations were not detected in the control subjects. Bioinformatics analysis predicted that the p.R131P mutation may not cause a pathogenic change, but the p.G160V mutation might be functionally deleterious. In intron 3 of the VSX1 gene, the nucleotide substitution of g.8326G>A was detected to be heterozygous in 3 cases of sporadic keratoconus and 4 cases of control and homozygous in 2 cases of sporadic keratoconus and 1 case of control. The variation of g.8326G>A belonged to a single polymorphism change of the VSX1 gene. Conclusions: The p.R131P detected in this study is a novel mutation of the VSX1 gene. Sequence variants of the VSX1 gene were identified for the first time in Chinese patients with sporadic keratoconus, but their precise role in disease causation requires further investigations. (Chin J Ophthalmol, 2018, 54: 212-217).
目的： 探讨中国人圆锥角膜VSX1基因的变异类型和变异特点。 方法： 横断面研究。收集就诊于浙江大学医学院附属邵逸夫医院眼科中心的50例散发性圆锥角膜患者做为病例组，其中男性29例，年龄（19.0±4.8）岁。选取50例健康人群作为对照组。对所有受检者采集外周静脉血，提取基因组DNA，应用聚合酶链反应和DNA直接测序技术，对VSX1基因全部5个外显子及外显子内含子拼接部，进行基因变异的检测；生物信息学分析这些基因变异对蛋白质结构和功能的影响。 结果： 发现VSX1基因4种碱基变异类型，包括二种错义变异和一种单核苷酸多态性改变：1例圆锥角膜患者在VSX1基因第1外显子氨基酸131位点精氨酸错义变异为脯氨酸（即p.R131P变异），此变异在对照组中未检出；2例圆锥角膜患者在VSX1基因第2外显子氨基酸160位点甘氨酸错义变异为缬氨酸（即p.G160V变异），此变异在对照组中未检出；在VSX1基因第3内含子中，碱基序列8326处发现G→A置换（即g.8326G>A变异），其中3例圆锥角膜患者和4例对照者为杂合性，2例圆锥角膜患者和1例对照为纯合性。生物信息学分析提示p.R131P变异系一新的VSX1基因突变类型，而p.G160V突变对蛋白质结构和功能可能有害；VSX1基因g.8326G>A变异为单核苷酸多态性改变。 结论： 在中国人圆锥角膜患者中发现了VSX1基因p.R131P新的杂合性突变，揭示了中国人群VSX1基因变异特征，但VSX1基因在中国人圆锥角膜发病中的作用尚需进一步研究。（中华眼科杂志，2018，54：212-217）.
Keywords: Eye Proteins; Homeodomain proteins; Keratoconus; Mutation; Polymorphism, single nucleotide.