Purpose: To evaluate the suggested role of the COL8A1 and COL8A2 genes in the pathogenesis of the corneal ectatic disorders keratoconus and keratoglobus through mutation screening in affected patients.
Methods: DNA extraction, polymerase chain reaction amplification, and sequencing of COL8A1 and COL8A2 were performed in 50 unrelated keratoconus and 2 unrelated keratoglobus patients.
Results: No sequence variations were identified in COL8A1 and COL8A2 in the 2 patients with keratoglobus. Screening of COL8A1 in keratoconus patients revealed a previously identified single nucleotide polymorphism (SNP; c.1850C>T; Pro535Pro), in 1 patient. Screening of COL8A2 in keratoconus patients revealed 7 previously described SNPs: c.14G>A (Gly3Arg); c.112G>A (Ala35Ala); c.1012C>G (Leu335Leu); c.1308G>A (Arg434His); c.1492G>A (Gly495Gly); c.1512C>T (Thr502Met); and c.1765C>T (Pro586Pro). Four novel sequence variants were also identified, each in 1 affected patient: c.38_40dupCTG (Leu11dup), also identified in an unaffected relative of the affected proband, c.667G>A (Gly220Gly), c.1588G>A (Pro527Pro), and c.2026C>T (Val673Val). None of the 3 novel synonymous substitutions identified in COL8A2 was predicted to produce a splice acceptor site.
Conclusions: The absence of pathogenic mutations in COL8A1 and COL8A2 in patients with keratoconus indicates that other genetic factors are involved in the pathogenesis of this corneal ectatic disorder.