Genetic analysis of Japanese primary open-angle glaucoma patients and clinical characterization of risk alleles near CDKN2B-AS1, SIX6 and GAS7

PURPOSE: To test the genetic association between Japanese patients with primary open-angle glaucoma (POAG) and the previously reported POAG susceptibility loci and to perform genotype–phenotype analysis. METHODS: Genetic associations for 27 SNPs from 16 loci previously linked to POAG were assessed using genome-wide SNP data of the primary cohort (565 Japanese POAG patients and 1,104 controls). Reproducibility of the assessment was tested in 607 POAG cases and 455 controls (second cohort) with a targeted genotyping approach. For POAG-associated variants, a genotype–phenotype correlation study (additive, dominant, recessive model) was performed using the objective clinical data derived from 598 eyes of 598 POAG patients. RESULTS: Among 27 SNPs from 16 loci previously linked to POAG, genotypes for total of 20 SNPs in 13 loci were available for targeted association study. Among 8 SNPs in 3 loci that showed at least nominal association (P < 5.00E-02) in the primary cohort, a representative SNP for each loci (rs2157719 for CDKN2B-AS1, rs33912345 for SIX6, and rs9913911 for GAS7) were selected. For these SNPs the association was found significant in both the second cohort analysis and meta-analysis. The genotype–phenotype analysis revealed significant correlations between CDKN2B-AS1 (rs2157719) and decreased intraocular pressure (β = -6.89 mmHg, P = 1.70E-04; dominant model) after multiple corrections. In addition, nominal correlation was observed between CDKN2B-AS1 (rs2157719) and optic nerve head blood flow (β = -0.54 and -0.67 arbitrary units (AU), P = 2.00E-02 and 1.39E-02), between SIX6 (rs33912345) and decreased total peripapillary retinal nerve fiber layer thickness (β = -2.16 and -2.82 μm, P = 4.68E-02 and 2.40E-02, additive and recessive model, respectively) and increased optic nerve head blood flow (β = 0.44 AU, P = 2.20E-02; additive model) and between GAS7 (rs9913911) and increased cup volume (β = 0.03 mm(3), P = 4.60E-02) and mean cup depth (β = 0.03 mm(3), P = 4.11E-02; additive model) and decreased pattern standard deviation (β = -0.87 dB, P = 2.44E-02; dominant model). CONCLUSION: The association between SNPs near GAS7 and POAG was found in Japanese patients for the first time. Clinical characterization of the risk variants is an important step toward understanding the pathology of the disease and optimizing treatment of patients with POAG.