HTRA1 Genotypes Associated With Risk of Neovascular Age-Related Macular Degeneration Independent of CFH and Smoking

Abstract

Purpose:: To examine if the PLEKHA1, LOC387715, and HTRA1 genes confer risk for neovascular age-related macular degeneration (AMD) when controlling for CFH genotype and smoking exposure.

Methods:: We ascertained 135 unrelated patients with AMD who had one sibling with normal maculae and was past the age at which the affected sibling was diagnosed, i.e., 135 extremely discordant sibpairs. CFH genotype (rs1061170) and smoking data were available for each sibship. Genotyping of PLEKHA1, LOC387715, and HTRA1 were performed by direct sequencing in the forward direction of exon 12, exon 1 and the 5’-UTR/promoter region respectively. Conditional logistic regression was used for statistical analysis. Additionally we analyzed 8 highly heterozygous microsatellite markers tightly linked to the 3 genes in this region. Identity-by-state (IBS) scores were calculated from the number of alleles shared between a sibpair for each of the 8 markers.

Results:: For the LOC387715/HTRA1 G>T variant (rs10490924), elevation of disease risk was found for both GT and TT genotypes compared to GG genotype (O.R: 5.6, 95% CI: 2.2-14.5, p=.0004 and O.R: 27.9, 95% CI: 7.0-110.0, p<.0001, respectively). Similar results were found for the recently reported HTRA1 G>A variant (rs11200638) and risk of AMD (AG vs. GG: O.R: 6.0, 95% CI: 2.3-15.5, p=.0002 and AA vs. GG: O.R: 33.8, 95% CI: 7.7-149.0, p<.0001). We also identified a previously unreported variant in HTRA1 to be associated with reduced risk of AMD by 25-fold if an individual was homozygous (p<.0001) and 6-fold if an individual was heterozygous for the minor allele (p<.0001) when compared to the homozygous major allele. When we included smoking and CFH in the model with any of these variants the significance and effect size were not modified with respect to risk of AMD. No significant association was observed between AMD and PLEKHA1. As for analysis of IBS scores, adjusting for multiple comparisons using a Bonferroni correction, only D10S1656 was found to be significantly associated with AMD (p<.0001).

Conclusions:: Independently of the CFH genotype and smoking, an individual’s risk of AMD could be increased or decreased depending on their genotype in the 10q26 region. To further clarify the contribution of LOC387715/HTRA1 to the risk of AMD, haplotype analysis of these significantly associated SNPs and the degree to which these SNPs are in linkage disequilibrium is ongoing.

Keywords: age-related macular degeneration • clinical (human) or epidemiologic studies: risk factor assessment • gene screening