Age-related macular degeneration (AMD) is a common cause of blindness in older individuals. To accelerate understanding of AMD biology and help design new therapies, we executed a collaborative genomewide association study, examining >17,100 advanced AMD cases and >60,000 controls of European and Asian ancestry. We identified 19 genomic loci associated with AMD with p<5×10−8 and enriched for genes involved in regulation of complement activity, lipid metabolism, extracellular matrix remodeling and angiogenesis. Our results include 7 loci reaching p<5×10−8 for the first time, near the genes COL8A1/FILIP1L, IER3/DDR1, SLC16A8, TGFBR1, RAD51B, ADAMTS9/MIR548A2, and B3GALTL. A genetic risk score combining SNPs from all loci displayed similar good ability to distinguish cases and controls in all samples examined. Our findings provide new directions for biological, genetic and therapeutic studies of AMD.

Purpose To evaluate the pharmacogenetic relationship between genotypes of single nucleotide polymorphisms (SNPs) known to be associated with age-related macular degeneration (AMD) and response to treatment with ranibizumab (Lucentis) or bevacizumab (Avastin) for neovascular AMD. Design Clinical trial. Participants 834 (73%) of 1149 patients participating in the Comparison of AMD Treatments Trials (CATT) were recruited through 43 CATT clinical centers. Methods Each patient was genotyped for SNPs rs1061170 (CFH), rs10490924 (ARMS2), rs11200638 (HTRA1), and rs2230199 (C3), using TaqMan SNP genotyping assays. Main Outcomes Measures Genotypic frequencies were compared to clinical measures of response to therapy at one year including mean visual acuity (VA), mean change in VA, ≥15 letter increase, retinal thickness, mean change in total foveal thickness, presence of fluid on OCT, presence of leakage on fluorescein angiography (FA), mean change in lesion size and mean number of injections administered. Differences in response by genotype were evaluated with tests of linear trend calculated from logistic regression models for categorical outcomes and linear regression models for continuous outcomes. To adjust for multiple comparisons, p≤0.01 was considered statistically significant. Results No statistically significant differences in response by genotype were identified for any of the clinical measures studied. Specifically, there were no high-risk alleles that predicted final VA or change in VA, the degree of anatomical response (fluid on OCT or FA, retinal thickness, change in total foveal thickness, change in lesion size) or the number of injections. Furthermore, a stepwise analysis failed to show a significant epistatic interaction among the variants analyzed; i.e., response did not vary by the number of risk alleles present. The lack of association was similar whether patients were treated with ranibizumab or bevacizumab or whether they received monthly or pro re nata (PRN) dosing. Conclusions Although specific alleles for CFH, ARMS2, HTRA1 and C3 may predict the development of AMD, they did not predict response to anti-vascular endothelial growth factor (VEGF) therapy.

Mutations in TRPM1 are found in humans with an autosomal recessive form of complete congenital stationary night blindness (cCSNB). The Trpm1(-/-) mouse has been an important animal model for this condition. Here we report a new mouse mutant, tvrm27, identified in a chemical mutagenesis screen. Genetic mapping of the no b-wave electroretinogram (ERG) phenotype of tvrm27 localized the mutation to a chromosomal region that included Trpm1. Complementation testing with Trpm1(-/-) mice confirmed a mutation in Trpm1. Sequencing identified a nucleotide change in exon 23, converting a highly conserved alanine within the pore domain to threonine (p.A1068T). Consistent with prior studies of Trpm1(-/-) mice, no anatomical changes were noted in the Trpm1(tvrm27/tvrm27) retina. The Trpm1(tvrm27/tvrm27) phenotype is distinguished from that of Trpm1(-/-) by the retention of TRPM1 expression on the dendritic tips of depolarizing bipolar cells (DBCs). While ERG b-wave amplitudes of Trpm1(+/-) heterozygotes are comparable to wild type, those of Trpm1(+/tvrm27) mice are reduced by 32%. A similar reduction in the response of Trpm1(+/tvrm27) DBCs to LY341495 or capsaicin is evident in whole cell recordings. These data indicate that the p.A1068T mutant TRPM1 acts as a dominant negative with respect to TRPM1 channel function. Furthermore, these data indicate that the number of functional TRPM1 channels at the DBC dendritic tips is a key factor in defining DBC response amplitude. The Trpm1(tvrm27/tvrm27) mutant will be useful for elucidating the role of TRPM1 in DBC signal transduction, for determining how Trpm1 mutations impact central visual processing, and for evaluating experimental therapies for cCSNB.

Homocysteine is an amino acid required for the metabolism of methionine. Excess homocysteine is implicated in cardiovascular and neurological disease and new data suggest a role in various retinopathies. Mice lacking cystathionine-beta-synthase (cbs−/−) have an excess of retinal homocysteine and develop anatomical abnormalities in multiple retinal layers, including photoreceptors and ganglion cells; heterozygous (cbs+/−) mice demonstrate ganglion cell loss and mitochondrial abnormalities in the optic nerve. The purpose of the present study was to determine whether elevated homocysteine, due to absent or diminished cbs, alters visual function. We examined cbs−/− (3 weeks) and cbs−+/− mice (5, 10, 15, 30 weeks) and results were compared to those obtained from wildtype (WT) littermates. Light- and dark-adapted ERGs were recorded along with dc-ERG to assess retinal pigment epithelial (RPE) function. The visual evoked potential (VEP) was used to assess transmission to the visual cortex. The amplitudes of the major ERG components were reduced in cbs−/− mice at age 3 weeks and VEPs were delayed markedly. These findings are consistent with the early retinal disruption observed anatomically in these mice. In comparison, at 3 weeks of age, responses of cbs+/− mice did not differ significantly from those of WT mice. Functional abnormalities were not observed in cbs+/− mice until 15 weeks of age, at which time amplitude reductions were noted for the ERG a- and b-wave and the light peak component, but not for other components generated by the RPE. VEP implicit times were delayed in cbs+/− mice at 15 and 30 weeks. The later onset of functional defects in cbs+/− mice is consistent with a slow loss of ganglion cells reported previously in the heterozygous mutant. Light peak abnormalities indicate that RPE function is also compromised in older cbs+/− mice. The data suggest that severe elevations of homocysteine are associated with marked alterations of retinal function while modest homocysteine elevation is reflected in modest and delayed alterations of retinal function. The work lays the foundation to explore the role of homocysteine in retinal diseases such as glaucoma and optic neuropathy.