Additive effects of genetic variants associated with intraocular pressure in primary open-angle glaucoma

<div><p>To investigate the association between the additive effects of genetic variants associated with intraocular pressure (IOP) and IOP, vertical cup-to-disc ratio (VCDR), and high tension glaucoma (HTG) or normal tension glaucoma (NTG) as phenotypic features of primary open-angle glaucoma (POAG), and to evaluate the clinical usefulness of the additive effects of IOP-related genetic variants for predicting IOP elevation, Japanese patients with HTG (n = 255) and NTG (n = 261) and 246 control subjects were genotyped for nine IOP-related genetic variants near <i>CAV2</i>, <i>GAS7</i>, <i>GLCCI1/ICA1</i>, <i>ABCA1</i>, <i>ARHGEF12</i>, <i>FAM125B</i>, <i>FNDC3B</i>, <i>ABO</i>, and <i>PTPRJ/AGBL2</i>. The total number of risk alleles of these genetic variants was calculated for each participant as a genetic risk score (GRS), and the association between the GRS and the maximum IOP, mean VCDR, and phenotype (HTG or NTG) of POAG was evaluated. As the GRS increased, the maximum IOP (P = 0.012) and VCDR (P = 0.010) significantly increased. The GRS (9.1±1.9) in patients with HTG was significantly higher (P = 0.011) than that (8.7±1.8) in control subjects. The patients with GRS≥12 as a cut-off value had a 2.54 times higher (P = 0.0085) risk on HTG (maximum IOP≥22mmHg) compared with all patients. The IOP-related GRS approach substantiated that the IOP and VCDR were increased by the additive effects of IOP-related genetic variants in POAG. The high IOP-related GRS in patients with HTG but not NTG shows that there are differences in the genetic background between HTG and NTG and supports the notion that the phenotype (HTG or NTG) in patients with POAG depends on the additive effects of IOP-related genetic variants. The above-mentioned cut-off value of IOP-related GRS may be clinically useful for predicting the risk of IOP elevation.</p></div

Association between the phenotype (HTG or NTG) of primary open-angle glaucoma and the additive effects of multi-locus IOP-related genetic variants.

<p>The IOP-related genetic risk score calculated as the total number of risk alleles of the 9 IOP-related genetic variants in patients with HTG was significantly higher (P = 0.040, analysis of variance followed by Bonferroni post hoc test) than that in the control subjects. IOP: intraocular pressure, HTG: high tension glaucoma, NTG: normal tension glaucoma.</p

Result of multiple linear regression analysis using the maximum IOP as a dependent variable.

<p>Result of multiple linear regression analysis using the maximum IOP as a dependent variable.</p

Demographic and clinical data in patients with POAG and control subjects.

<p>Demographic and clinical data in patients with POAG and control subjects.</p

Result of multiple linear regression analysis using the VCDR as a dependent variable.

<p>Result of multiple linear regression analysis using the VCDR as a dependent variable.</p

Association between the IOP-related GRS and the relative ratio of HTG patients to control subjects.

<p>When the ratio (255 HTG patients/246 control subjects) of all HTG patients (maximum IOP≥22mmHg) to all control subjects (maximum IOP≤21mmHg) was set as 1, the ratio (29 HTG patients/11 control subjects) of HTG to control in patients with the IOP-related GRS calculated as the total number of risk alleles of the 9 IOP-related genetic variants ≥12 was 2.54, which was significantly larger (Chi-square test) than that in all patients. IOP: intraocular pressure, GRS: genetic risk score, HTG: high tension glaucoma.</p

Result of a multiple linear regression analysis using the maximum IOP as a dependent variable.

<p>Result of a multiple linear regression analysis using the maximum IOP as a dependent variable.</p

Design of the study.

<p>The study comprised 3 steps. In the first step, an association study of known POAG-related loci was carried out using the genome-wide SNP data from SNP array (cases) and a previous genetic study (control).[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0186678#pone.0186678.ref025" target="_blank">25</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0186678#pone.0186678.ref027" target="_blank">27</a>] In the second step, 3 candidate risk SNPs were genotyped in the cases and controls to test for the reproducibility. Then a clinical correlation study was performed in the third step. SNP, single nucleotide polymorphism; POAG, primary open-angle glaucoma, HFA, Humphrey Field Analyzer, RNFL, retinal nerve fiber layer thickness, OCT, optical coherence tomography, SFC, stereoscopic fundus camera, LSFG, laser speckle flowgraphy.</p

Clinical demographics of patients in the genotype–phenotype correlation study.

<p>Clinical demographics of patients in the genotype–phenotype correlation study.</p

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

<div><p>Purpose</p><p>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.</p><p>Methods</p><p>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.</p><p>Results</p><p>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 (<i>P</i> < 5.00E-02) in the primary cohort, a representative SNP for each loci (rs2157719 for <i>CDKN2B-AS1</i>, rs33912345 for <i>SIX6</i>, and rs9913911 for <i>GAS7</i>) 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 <i>CDKN2B-AS1</i> (rs2157719) and decreased intraocular pressure (β = -6.89 mmHg, <i>P</i> = 1.70E-04; dominant model) after multiple corrections. In addition, nominal correlation was observed between <i>CDKN2B-AS1</i> (rs2157719) and optic nerve head blood flow (β = -0.54 and -0.67 arbitrary units (AU), <i>P</i> = 2.00E-02 and 1.39E-02), between <i>SIX6</i> (rs33912345) and decreased total peripapillary retinal nerve fiber layer thickness (β = -2.16 and -2.82 μm, <i>P</i> = 4.68E-02 and 2.40E-02, additive and recessive model, respectively) and increased optic nerve head blood flow (β = 0.44 AU, <i>P</i> = 2.20E-02; additive model) and between <i>GAS7</i> (rs9913911) and increased cup volume (β = 0.03 mm³, <i>P</i> = 4.60E-02) and mean cup depth (β = 0.03 mm³, <i>P</i> = 4.11E-02; additive model) and decreased pattern standard deviation (β = -0.87 dB, <i>P</i> = 2.44E-02; dominant model).</p><p>Conclusion</p><p>The association between SNPs near <i>GAS7</i> 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.</p></div