Abstract
Abstract: :
Purpose: To identify mutations in the BIGH–3 gene in Indian patients with lattice and granular corneal dystrophy and to derive genotype–phenotype correlations. Methods: Forty unrelated patients were studied, nineteen with lattice corneal dystrophy (LCD) and twenty–one with granular corneal dystrophy (GCD). Clinical examination was performed on all patients and available family members and peripheral blood samples were collected for isolation of genomic DNA. The diagnosis of lattice or granular corneal dystrophy was made on the basis of clinical examination and in cases where corneal grafts were performed, confirmed by histopathological evaluation of corneal buttons. Exons and flanking intron sequences of the BIGH–3 gene were amplified by PCR using specific primers. PCR products were screened by the method of single–strand conformation polymorphism and fragments showing altered mobility relative to controls directly sequenced by automated methods. Sequences were compared with controls. Mutations were confirmed by screening at least 50 unrelated normal controls. Results: Mutations were identified in 15/19 patients with LCD and in all 21 patients with GCD. In LCD, mutation of arginine–124 to cysteine (R124C) was found in 8/19 patients, and histidine–626 to arginine (H626R) in 2/19 patients. In addition, 3 novel heterozygous mutations found were glycine–594–valine (G594V) in 2/19 patients, valine–539–aspartic acid (V539D) in 1 patient, and deletion of valine–624,625 (V624–625del) in 1 patient. A novel homozygous change of glycine–623 to serine (G623S) was found in 1 patient with a family history suggestive of autosomal recessive inheritance. In GCD, 20/21 patients had a mutation of arginine–555 to tryptophan (R555W) and 1 patient with a clinical diagnosis of Reis–Bucklers dystrophy, had the R124L mutation. Four novel SNPs were also found. The G594V mutation was associated with late onset combined with deep stromal opacities. V624–625del and G623S mutations occurred in patients who had amyloid deposits that appeared as granular opacities with no distinct lattice lines. Conclusion: Genotype–phenotype correlations revealed that the novel mutations identified in this study are associated with distinct phenotypes. R124C and R555W appear to be the predominant mutations causing LCD and GCD respectively in the Indian population.
Keywords: cornea: basic science • genetics • mutations