Mutation spectrum of CYP1B1 in North Indian congenital glaucoma patients

PURPOSE Mutations in Cytochrome P450 (CYP1B1) are a predominant cause of congenital glaucoma. This study was planned with the aim to identify the mutation profile of CYP1B1 in North Indian primary congenital glaucoma (PCG) patients. METHODS After ethical clearance, 50 congenital glaucoma patients and 50 ethnically matched controls were recruited in this study. Genomic DNA was isolated from the blood and trabecular meshwork, and CYP1B1 was screened for the six most prevalent mutations (termination at 223 [Ter@223], Gly61Glu, Pro193Leu, Glu229Lys, Arg368His, and Arg390Cys) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). DNA sequencing was done to identify other mutations and for confirmation of RFLP positive samples. RESULTS On PCR-RFLP, 21/50 cases (42%) were found positive for one or more of these mutations. However, on sequencing, we found that 23/50 (46%) harbored the CYPIB1 mutations. Ter@223 was found in 18%, p.R390H in 16%, and p.R368H in 8% of cases. Three novel mutations, p.L24R, p.F190L, and p.G329D, were identified by DNA sequencing. Leucine, phenylalanine, and glycine are conserved at the 24th, 190th, and 329th position in the CYP1B1 protein in different species, suggestive of important functions at these loci. Ter@223 was found to be the most prevalent mutation in our patients while p.R368H was most prevalent in southern India. The difference in frequency and mutation profile may be due to the heterogeneous Indian population. Pathogenic CYP1B1 mutations impair anterior chamber development and differentiation by blocking the aqueous outflow and raising intraocular pressure (IOP). CONCLUSIONS Three novel mutations were identified in this study. Studies of pathogenic sequence variants in CYP1B1 in different populations may contribute to a better understanding of the disease pathogenesis. This may lead to the development of novel therapeutic approaches in the near future.