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M. He, Y.-M. Hur, J. Zhang, D. Wang, B. Li, J. Ge; Is There Shared Genetic Determinant of Narrow Angle and Myopia? The Guangzhou Twin Eye Study. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5427. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Angle-closure and myopia have been traditionally considered as two separate phenotypes with different mechanism and determinants although the anatomical features of these two diseases are closely associated with each other. The purposes of the present study are to determine whether common sets of genes are operating in the angle closure traits and myopia-related traits and to estimate the extent to which common genetic and/of environmental factors influence the relationships
The study participants were recruited from the Guangzhou Twin Registry and examined during the 2nd year phenotypic collection. ASOCT and custom software was used to quantify the anterior chamber parameters. Angle opening distance (AOD) at the location 500 µm anterior to scleral spur was selected as the measure of degree of angle width. Anterior chamber depth (ACD) and axial length (AL) were measured using a Zeiss IOLMaster. We computed twin correlations and cross-trait cross-twin correlations for monozygotic (MZ) and dizygotic (DZ) twins and carried out model-fitting analyses using a multivariate Cholesky model. All correlations were corrected for age and sex. The right eye was arbitrarily selected to represent the phenotypic characteristics of the specific individual.
918 twins aged 8-16 years were available for analysis, which included 304 MZ and 155 DZ pairs. The phenotypic correlations among AL, ACD, and AOD were high as well as significant, ranging from 0.39 to 0.52. MZ twin correlations were significantly greater than DZ twin correlations for all three phenotypes, suggesting substantial genetic influences. MZ cross-twin cross-trait correlations were all greater than the corresponding DZ correlations, indicating that shared genetic factors play an important role in the covariations among the three phenotypes. When we standardized the Cholesky additive genetic factor loadings, of 80% of heritability for AOD, 17% were shared with the genetic factors that influence AL, 28% were in common with the genetic factors that affect ACD, and the remaining 35% were those genetic factors unique to AOD. Likewise, of 90% of heritability estimate for ACD, 31% were shared with the genetic factors that influence AL and 59% were those genetic factors unique to ACD.
Genetic covariance for angle closure and myopic related quantitative traits was substantial, suggesting that shared genes may determine the relationships.
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