[A novel VSX1 gene mutation identified in a sporadic keratoconus patient from China]

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).