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M.A. Grassi, J.H. Fingert, J.C. Folk, T.E. Scheetz, A.M. Shire, R. Ritch, S.K. West, K. Kawase, R.F. Mullins, E.M. Stone; Ethnic and Phenotypic Frequencies of Complement Factor H Polymorphism Y402H . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4164.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have demonstrated that the Y402H polymorphism in the complement factor H (CFH) gene is associated with an approximately 3–fold increased risk for age–related macular degeneration (AMD) in Caucasians of predominantly European descent. The prevalence of AMD varies widely among persons of different ethnicities. In this study we sought to determine the frequency of this polymorphism in control populations of Caucasians, African Americans, Hispanics, Somalis, and Japanese. Moreover, we investigated whether specific AMD phenotypes are associated with this polymorphism.
Normal control populations were assembled for each ethnic group: Caucasian (n=148), Somali (n=128), African American (n=75), Hispanic (n=100), and Japanese (n=82). Individuals were genotyped using NIaIII restriction digestion. The frequency of the histidine (His) allele at position 402 of the CFH gene was determined. A bioinformatic approach was used to identify single nucleotide polymorphisms in linkage disequilibrium with Y402H from the HapMap in order to validate the findings. A total of 508 individuals with AMD were included in the phenotypic arm of the study. Fundus photos were graded using the following four categories: choroidal neovascularization, geographic atrophy, AREDS grade 3, and classic cuticular drusen. The Chi–Square test was used to analyze both genotype and allele frequency.
We found widely discordant frequencies of the His allele between the different ethnic groups: Japanese 7%, Hispanics 17%, African–Americans 35%, Caucasians 34%, and Somalis 34%. Allele frequencies generated by analysis of the HapMap were consistent with these findings. His allele frequency in our AMD cohort was 57%. The high–risk homozygous (His/His) genotype was found in 32% of patients. We did not find a significant relationship between CFH genotype and the four conventional phenotypes considered in this study.
This study suggests that there are other yet unidentified genetic factors important in the pathogenesis of AMD that may mitigate the effects of the Y402H polymorphism. Allele frequency of the Y402H polymorphism in our AMD cohort supports previously published findings. No statistically significant association between CF genotype and four different AMD phenotypes was identified.
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