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(Hypertension. 2009;54:788.)
© 2009 American Heart Association, Inc.

Original Articles

Quantitative Genetic Analysis of the Retinal Vascular Caliber

The Australian Twins Eye Study

Cong Sun; Gu Zhu; Tien Y. Wong; Alex W. Hewitt; Jonathan B. Ruddle; Lauren Hodgson; Grant W. Montgomery; Terri L. Young; Christopher J. Hammond; Jamie E. Craig; Nicholas G. Martin; Mingguang He; David A. Mackey

From the Centre for Eye Research Australia (C.S., T.Y.W., A.W.H., J.B.R., L.H., D.A.M.), University of Melbourne, Melbourne, Victoria, Australia; Queensland Institute of Medical Research (G.Z., G.W.M., N.G.M.), Brisbane, Queensland, Australia; Singapore Eye Research Institute (T.Y.W.), Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Duke Eye Center (T.L.Y.), Duke University Medical Center, Duke University, Durham, NC; Department of Twin Research and Genetic Epidemiology Unit (C.J.H.), King’s College London, London, United Kingdom; National Health and Medical Research Council Centre for Clinical Eye Research (J.E.C.), Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia; State Key Laboratory of Ophthalmology (M.H.), Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China; Discipline of Medicine (D.A.M.), University of Tasmania, Tasmania, Australia.

Correspondence to David A. Mackey, Centre for Eye Research Australia, University of Melbourne, Department of Ophthalmology, Royal Victorian Eye and Ear Hospital, 1/32 Gisborne St, East Melbourne, Victoria 3002, Australia. E-mail D.Mackey{at}utas.edu.au

Research into the genetic effects and specific genes associated with retinal vascular caliber, a risk marker of cardiovascular diseases, may provide new insights into the genetic contribution of early microvascular disease. A combined 374 monozygotic and 536 dizygotic twin pairs and 322 siblings from the Twins Eye Study in Tasmania and the Brisbane Adolescent Twin Study underwent complete ophthalmic examinations, including retinal photography, and bilateral retinal vascular caliber was measured. Structural equation modeling was used to estimate the heritability. Genome-wide linkage analysis was conducted on 836 individuals from 381 Brisbane Adolescent Twin Study families, with adjustments for age, sex, and other covariates. The heritabilities for the retinal arteriolar caliber were 59.4% (95% CI: 53.2% to 64.7%) and 56.5% (95% CI: 50.1% to 61.9%) in the Twins Eye Study in Tasmania and the Brisbane Adolescent Twin Study, respectively, and for venular caliber they were 61.7% (95% CI: 55.6% to 67.0%) and 64.2% (95% CI: 58.7% to 68.8%), respectively, after adjusting for age, sex, and body mass index. Two multipoint peaks detected on chromosomes 3p12.3 and 8p23.1 for retinal arteriolar caliber had suggestive linkage, with the highest multipoint peak logarithm of odds score of 2.24 on chromosome 8p23.1 (genome-wide P=7.0x10^–4). Two suggestive logarithm of odds scores for venular caliber were identified on chromosomes 2p14 and 9q21.13. The largest multipoint logarithm of odds score was 2.69 on chromosome 2p14 (genome-wide P=2.0x10^–4). In this large twin population, genetic factors appear to play a significant role in the variation of retinal vascular caliber. Several putative loci were identified for the retinal vascular caliber.

Key Words: twins • heritability • retinal vascular caliber • genome-wide linkage analysis • genetics