Evaluation of Nitric Oxide Synthase 3 (NOS3) as a candidate glaucoma gene

Abstract

Abstract: : Purpose: Nitric Oxide Synthase 3 (NOS3) maps to 7q35 within the GLC1F locus at 7q35-36. A common variant, Glu298Asp, and sequence variants in promoter region have been previously associated with coronary spasm in some populations. We evaluated NOS3 as a candidate gene for primary open angle glaucoma. Methods: We ran microsatellite markers around the NOS3 locus on chromosome 7 to examine haplotypes. Using the genotypes from the microsatellite markers we haplotyped 28 families (137 White from 25 families, 14 African-American from 3 families) in this area to enrich the study population for families that showed evidence for this region influencing susceptibility to glaucoma. Through this process we excluded 10 families. We screened affected probands from 18 families (16 White probands from 16 families, 2 African-American probands from 2 families) for NOS3 polymorpisms.We also screened DNA from 81 White and15 African-American age matched controls. We carried out mutation screening of the NOS3 promoter, exons and splice sites by direct sequencing. Results: We identified a G to T polymorphism in exon 7 that causes a Glu to Asp amino acid substitution in codon 298 (Glu298Asp). The frequencies of the NOS3 GG, GT, and TT genotypes were 0.38, 0.44 and 0.18 respectively in the affected subjects, and 0.48, 0.35 and 0.17 respectively in the control subjects. We also identified the sequence variant -786T to C in the promoter region (Marsden, JBC, 268,17478-88,1993) . The frequencies of the NOS3 TT, TC, CC genotypes were 0.55, 0.39 and 0.06 respectively in the affected subjects, and 0.37, 0.50 and 0.13 respectively in the control subjects. These allele frequencies are different from previously published data on an Asian population, but similar data published on an Australian population. Conclusion: The odds ratios show that there is no statistically significant increase in the odds of having glaucoma associated with either of these base changes. To date there is no evidence to suggest that there is an association with these sequence variants and glaucoma. We are currently investigating DNA from additional glaucoma subjects and normal control subjects. CR: None Support: NIH-EY11671, Research to Prevent Blindness, Glaucoma Research Foundation, Japan Eye Bank Association

Keywords: 420 genetics • 335 candidate gene analysis • 491 nitric oxide