Purpose: To perform mutational screening of the visual system homeobox gene 1 (VSX1; MIM#605020) in patients with sporadic and familial keratoconus (MIM#148300) in a European population and, for the first time, report the mutational analysis of the two newly identified VSX1exons.
Methods: VSX1sequence variants in patients with keratoconus were evaluated by direct sequencing of the entire coding region, including two novel exons. In familial keratoconus cases, segregation of potentially pathogenic VSX1variants was assessed to determine pathogenicity. Transcript analysis was carried out on splice site and synonymous sequence variants not detected in controls.
Results: A total of 66 unrelated patients with keratoconus from the European population (27 with familial keratoconus; 39 with sporadic keratoconus) were analysed for VSX1 mutations. Four sequence variants were not observed in 100 healthy control individuals: c.432C>G (p.D144E), c.479G>A (p.G160D), c.789C>T (p.S263S), and an intronic change c.844-13T>A (numbered with respect to NM_014588). Segregation was not detected for p.D144E and c.844-13T>A. The change in p.G160D was observed in two patients with sporadic keratoconus. Although predicted to alter VSX1 splicing, p.S263S had no effect on transcript processing. Four known SNPs were detected and the following polymorphic variants were observed in keratoconus patients and controls: c.711T>A (NM_199425; p.P237P), c.844-5_-6insT (NM_014588), c.*28G>T (DQ854811/DQ854812), and c.*50G>A (DQ854809/DQ854810).
Conclusions: VSX1has a minor role in keratoconus pathogenesis. The pathogenicity of p.G160D remains controversial and this change may represent a rare polymorphism or genetic modifier. Further evidence is provided that the previously reported variant, p.D144E, is a polymorphism.