Low frequency of myocilin mutations in Indian primary open-angle glaucoma patients

Glaucoma is one of the major causes of blindness in the Indian population. Mutations in the myocilin (MYOC) gene have been reported in different populations. However, reports on MYOC mutations in Indian primary open-angle glaucoma (POAG) patients and juvenile open-angle glaucoma (JOAG) patients are sparse. We therefore screened 100 unrelated POAG/JOAG patients for MYOC mutations. Patients with POAG/JOAG were clinically diagnosed. Genomic DNA from such patients was collected and studied for MYOC mutations by direct sequencing. Nucleotide variations were compared with unrelated healthy controls by restriction enzyme digestion. Secondary structure prediction for the sequence variants was performed by Chou-Fasman method. A novel mutation in exon 1 (144 G-->A) resulting in Gln48His substitution was observed in 2% of the patients. Four other polymorphisms were also observed. The novel mutation was seen in four other affected family members of a JOAG patient. The novel mutation was found to alter the secondary structure in the glycosaminoglycan initiation site of the protein. MYOC mutations were found in 2% of the population studied. MYOC gene may not be playing a significant role in causing POAG in the Indian population.