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R. Wojciechowski, E. Ciner, G. Ibay, J. E. Bailey-Wilson, D. Stambolian; Genomewide Scan of Ocular Refraction in African-Americans Shows Linkage to Chromosome 7p15. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3238.
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Refractive development is influenced by environmental and genetic factors. Genetic studies have identified a number of loci linked to myopia and ocular refraction. We performed quantitative trait locus linkage analyses in an African-American (AA) population to identify genomic regions responsible for refraction.
We recruited 493 AA individuals in 96 families to participate in the study. Ascertainment criteria were designed to enrich the sample for myopia. Genotyping with 387 microsatellite markers was performed on 398 participants. The mean spherical equivalent refractive error among genotyped individuals was -2.87 D (SD=3.58) and myopia of at least 1 D was present in 267 (67%) participants. Multipoint, regression-based, linkage analyses were carried-out on a logarithmic transformation of the refraction using the statistical package MERLIN-REGRESS. Empirical significance levels were determined by conducting 4,898 whole-genome gene-dropping simulations. Linkage analyses were repeated after clustering families into two subgroups based on admixture proportions as determined by the software package STRUCTURE.
The maximum linkage signal was seen at 47 cM on chromosome 7 (LOD=5.87, p=.000065). Secondary peaks (LOD>2, p<.005) were observed on chromosomes 2, 3 and 10. Only the signal on chr. 7 (genomewide p=.026) met statistical significance criterion for genomewide significance. Stratified analyses based on admixture proportions did not significantly alter the LOD score profile in this linked region.
We identified a quantitative trait locus for ocular refraction in an African-American population on chr. 7p15. One previous study in a Caucasian sample reported linkage to a nearby region, suggesting that this locus may contain polymorphisms that mediate refraction across populations. The genomic region bounded by the markers flanking our maximum linkage peak spans more than 15 megabases and contains approximately 170 known genes.
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