Genome-wide association study of advanced age-related macular degeneration identifies a role of the hepatic lipase gene (LIPC)

Abstract

Advanced age-related macular degeneration (AMD) is the leading cause of late onset blindness. We present results of a genome-wide association study of 979 advanced AMD cases and 1,709 controls using the Affymetrix 6.0 platform with replication in seven additional cohorts (totaling 5,789 unrelated cases and 4,234 unrelated controls). We also present a comprehensive analysis of copy-number variations and polymorphisms for AMD. Our discovery data implicated the association between AMD and a variant in the hepatic lipase gene (LIPC) in the high-density lipoprotein cholesterol (HDL) pathway (discovery P = 4.53e-05 for rs493258). Our LIPC association was strongest for a functional promoter variant, rs10468017, (P = 1.34e-08), that influences LIPC expression and serum HDL levels with a protective effect of the minor T allele (HDL increasing) for advanced wet and dry AMD. The association we found with LIPC was corroborated by the Michigan/Penn/Mayo genome-wide association study; the locus near the tissue inhibitor of metalloproteinase 3 was corroborated by our replication cohort for rs9621532 with P = 3.71e-09. We observed weaker associations with other HDL loci (ABCA1, P = 9.73e-04; cholesterylester transfer protein, P = 1.41e-03; FADS1-3, P = 2.69e-02). Based on a lack of consistent association between HDL increasing alleles and AMD risk, the LIPC association may not be the result of an effect on HDL levels, but it could represent a pleiotropic effect of the same functional component. Results implicate different biologic pathways than previously reported and provide new avenues for prevention and treatment of AMD.

Fig. 1.

Immunoblot of hepatic lipase antibody (H-70, SC-21007) against human whole-protein extracts. Lane 1, macular retina; lane 2, peripheral retina; lane 3, RPE–choroid; lane 4, liver. Lanes 1–3 were normalized against actin.

Fig. 2.

(A) Distribution of hepatic lipase C (red) in central monkey retina using a rabbit polyclonal antibody (Cat. #SC-21007) raised against amino acids 91–160 of human origin. This antibody labels all retina neurons, especially ganglion cells of central monkey retina, but does not label Mueller cells (identified by glutamine synthetase; green). (Scale bar, 20 μm.) (B) Distribution of hepatic lipase C (red) in peripheral monkey retina. (Scale bar, 20 μm.) (C) High-magnification images of photoreceptors show immunoreactivity for antihepatic lipase C (red). (Scale bar, 10 μm.) (D) High-magnification images of ganglion cells show immunoreactivity for antihepatic lipase C (red). (Scale bar, 10 μm.) Cones, defined by primate cone arrestin labeling (mAb 7G6; green in C), are positive for hepatic lipase C. However, rods reveal a strong punctate label (red) in the outer nuclear layer as well as over inner and outer segments. In D, strong immunoreactivity for hepatic lipase C (red) observed in ganglion-cell somata and axons of the nerve fiber layer (NFL) contrasts with that of a Mueller cell marker (green; glutamine synthetase; BD Transduction).