Euijung Ryu

E2-2 protein and Fuchs's corneal dystrophy

BACKGROUND Fuchss corneal dystrophy (FCD) is a leading cause of corneal transplantation and affects 5% of persons in the United States who are over the age of 40 years. Clinically visible deposits called guttae develop under the corneal endothelium in patients with FCD. A loss of endothelial cells and deposition of an abnormal extracellular matrix are observed microscopically. In advanced disease, the cornea swells and becomes cloudy because the remaining endothelial cells are not sufficient to keep the cornea dehydrated and clear. Although rare genetic variation that contributes to both early-onset and typical late-onset forms of FCD has been identified, to our knowledge, no common variants have been reported. METHODS We performed a genomewide association study and replicated the most significant observations in a second, independent group of subjects. RESULTS Alleles in the transcription factor 4 gene (TCF4), encoding a member of the E-protein family (E2-2), were associated with typical FCD (P=2.3x10(-26)). The association increased the odds of having FCD by a factor of 30 for persons with two copies of the disease variants (homozygotes) and discriminated between case subjects and control subjects with about 76% accuracy. At least two regions of the TCF4 locus were associated independently with FCD. Alleles in the gene encoding protein tyrosine phosphatase receptor type G (PTPRG) were associated with FCD (P=4.0x10(-7)), but the association did not reach genomewide significance. CONCLUSIONS Genetic variation in TCF4 contributes to the development of FCD. (Funded by the National Eye Institute and others.)

Genetic control of the alternative pathway of complement in humans and age-related macular degeneration

Activation of the alternative pathway of complement is implicated in common neurodegenerative diseases including age-related macular degeneration (AMD). We explored the impact of common variation in genes encoding proteins of the alternative pathway on complement activation in human blood and in AMD. Genetic variation across the genes encoding complement factor H (CFH), factor B (CFB) and component 3 (C3) was determined. The influence of common haplotypes defining transcriptional and translational units on complement activation in blood was determined in a quantitative genomic association study. Individual haplotypes in CFH and CFB were associated with distinct and novel effects on plasma levels of precursors, regulators and activation products of the alternative pathway of complement in human blood. Further, genetic variation in CFH thought to influence cell surface regulation of complement did not alter plasma complement levels in human blood. Plasma markers of chronic activation (split-products Ba and C3d) and an activating enzyme (factor D) were elevated in AMD subjects. Most of the elevation in AMD was accounted for by the genetic variation controlling complement activation in human blood. Activation of the alternative pathway of complement in blood is under genetic control and increases with age. The genetic variation associated with increased activation of complement in human blood also increased the risk of AMD. Our data are consistent with a disease model in which genetic variation in the complement system increases the risk of AMD by a combination of systemic complement activation and abnormal regulation of complement activation in local tissues.

Contribution of copy number variation in the regulation of complement activation locus to development of age-related macular degeneration.

PURPOSE To develop an assay for determining the number of copies of the genes encoding complement factor H related 3 (CFHR3) and 1 (CFHR1) and determine the contribution of copy number variation (CNV) at CFHR3 and CFHR1 to the development of age-related macular degeneration (AMD). METHODS A multiplex ligation-dependent probe amplification (MLPA) assay was developed to quantify the number of copies of CFHR3 and CFHR1 in humans. Subjects with (n = 252) and without (n = 249) AMD were genotyped using the assay, and the impact on AMD risk was evaluated. RESULTS The MLPA assay provided a consistent estimate of the number of copies of CFHR3 and CFHR1 in 500 of the 501 samples. Four different combinations of CNVs were observed with frequencies as follows: both CFHR3 and CFHR1 deletion (14%), CFHR3-only deletion (0.4%), CFHR1-only deletion (1.1%), and CFHR1 duplication (0.1%). Deletion of both copies of CFHR3 and CFHR1 decreased the odds of having AMD eightfold (95% CI 2-36) and always occurred on a protective haplotype, never on the risk haplotype tagged by the Y402H risk allele in CFH. The protection conferred by deletion of CFHR3 and CFHR1 could not be distinguished from the absence of the risk haplotype. CONCLUSIONS Both deletions and duplications of genes in the regulation of complement activation locus segregated in Caucasians. Deletion of CFHR3 and CFHR1 protected against the development of AMD at least in part because the deletion tagged a protective haplotype and did not occur on the risk haplotype.

The Association Between Complement Component 2/Complement Factor B Polymorphisms and Age-related Macular Degeneration: A HuGE Review and Meta-Analysis

The authors performed a systematic review of the association of complement component 2(C2)/complement factor B (CFB) gene polymorphisms with age-related macular degeneration (AMD). In total, data from 19 studies published between 2006 and 2011 were pooled for 4 polymorphisms: rs9332739 and rs547154 in the C2 gene and rs4151667 and rs641153 in the CFB gene. Data extraction and assessments for risk of bias were independently performed by 2 reviewers. Allele frequencies and allele and genotypic effects were pooled. Heterogeneity and publication bias were explored. Pooled minor allele frequencies for all 4 SNPs were between 4.7% and 9.6% for all polymorphisms, except for an Indian population in which the C allele at rs9332739 was the major allele. For the C2 polymorphisms, the minor C allele at rs9332739 and the minor T allele at rs547154 carried estimated relative risks (odds ratios) of 0.55 (95% confidence interval (CI): 0.46, 0.65) and 0.47 (95% CI: 0.39, 0.57), respectively. For the CFB polymorphisms, the minor A alleles at rs4151667 and rs614153 carried estimated risks of 0.54 (95% CI: 0.45, 0.64) and 0.41 (95% CI: 0.34, 0.51), respectively. These allele effects contributed to an absolute lowering of the risk of all AMD in Caucasian populations by 2.0%-6.0%. This meta-analysis provides a robust estimate of the protective association of C2/CFB with AMD.