Genetic association study of age-related macular degeneration in the Spanish population

Abstract

Purpose: To investigate new genetic risk factors and replicate reported associations with advanced age-related macular degeneration (AMD) in a prospective case-control study developed with a Spanish cohort.

Methods: Three hundred and fifty-three unrelated patients with advanced AMD (225 with atrophic AMD, 57 with neovascular AMD, and 71 with mixed AMD) and 282 age-matched controls were included. Functional and tagging SNPs in 55 candidate genes were genotyped using the SNPlex™ genotyping system. Single SNP and haplotype association analysis were performed to determine possible genetic associations; interaction effects between SNPs were also investigated.

Results: In agreement with previous reports, ARMS2 and CFH genes were strongly associated with AMD in the studied Spanish population. Moreover, both loci influenced risk independently giving support to different pathways implicated in AMD pathogenesis. No evidence for association of advanced AMD with other previous reported susceptibility genes, such as CST3, CX3CR1, FBLN5, HMCN1, PON1, SOD2, TLR4, VEGF and VLDLR, was detected. However, two additional genes appear to be candidate markers for the development of advanced AMD. A variant located at the 3' UTR of the FGF2 gene (rs6820411) was highly associated with atrophic AMD, and the functional SNP rs3112831 at ABCA4 showed a marginal association with the disease.

Conclusion: We performed a large gene association study in advanced AMD in a Spanish population. Our findings show that CFH and ARMS2 genes seem to be the principal risk loci contributing independently to AMD in our cohort. We report new significant associations that could also influence the development of advanced AMD. These findings should be confirmed in further studies with larger cohorts.

Figure 1. LD and haplotype maps of the CFH locus in this Spanish population

A schematic representation of the intron/exon structure of the CFH gene is indicated above the LD plot. Relative positions of studied SNPs are also indicated. Each box provides r² values with darker red shades representing stronger LD. Haplotype association analysis in cases and controls were performed for the single haplotype block found at this locus. All of the haplotypes with a frequency of >1% are displayed. The estimated frequencies of the haplotype in cases and controls, ORs, 95% CI and P-values are also shown. The risk haplotype (H1) is shown in red shading, and the protective haplotypes (H3, H4 and H5) are shown in green shading. Alleles exclusively found in these risk and protective haplotypes are boxed.

Figure 2. LD and haplotype maps of the FGF2 locus in this Spanish population

A schematic representation of the intron/exon structure of the FGF2 and NUDT6 genes with the relative positions of tagSNPs, is indicated above the LD plot. Each box provides r² values with darker red shades representing stronger LD. Haplotype association analysis in cases and controls are also performed on the two haplotype blocks found at this locus. All of the haplotypes with a frequency of >1% are displayed. The estimated haplotypic frequencies in cases and controls, P-values, ORs and 95% CI are also shown. The risk haplotype (H3) is shown in red shading remarking in a box the risk allele at rs6820411.