Twin Research

Articles

Height Discordance in Monozygotic Females is not Attributable to Discordant Inactivation of X-linked Stature Determining Genes

S.C. Healeya1, K.M. Kirka2, V.J. Hylanda3, C.F. Munnsa4, A.K. Hendersa5, J.A. Batcha6, A.C. Heatha7, N.G. Martina8 c1 and I.A. Glassa9

a1 Molecular Genetics Section, Pathology Department, Royal Brisbane Hospital.

a2 Queensland Institute of Medical Research and Joint Genetics Program, University of Queensland, Brisbane, Australia.

a3 Molecular Genetics Section, Pathology Department, Royal Brisbane Hospital.

a4 Royal Children's Hospital, Brisbane, Australia.

a5 Queensland Institute of Medical Research and Joint Genetics Program, University of Queensland, Brisbane, Australia.

a6 Royal Children's Hospital, Brisbane, Australia.

a7 Department of Psychiatry, Washington Unviersity School of Medicine, St Louis, Missouri, USA.

a8 Queensland Institute of Medical Research and Joint Genetics Program, University of Queensland, Brisbane, Australia. nickM@qimr.edu.au

a9 Queensland Clinical Genetics Service, Brisbane, Australia.

Abstract

We tested the hypothesis that X-linked genes determining stature which are subject to skewed or non-random X-inactivation can account for discordance in height in monozygotic female twins. Height discordant female monozygotic adult twins (20 pairs) were identified from the Australian Twin Registry, employing the selection criteria of proven monozygosity and a measured height discordance of at least 5 cm. Differential X-inactivation was examined in genomic DNA extracted from peripheral lymphocytes by estimating differential methylation of alleles at the polymorphic CAG triplet repeat of the Androgen receptor gene (XAR). There were 17/20 MZ pairs heterozygous at this locus and informative for analysis. Of these, 10/17 both had random X-inactivation, 5/17 showed identical X-inactivation patterns of non random inactivation and 2/17 (12%) showed discordant X-inactivation. There was no relationship between inactivation patterns and self-report chorionicity. We conclude that non-random X-inactivation does not appear to be a major contributor to intra-pair height discordance in female MZ twins.

(Received November 07 2000)

(Accepted December 05 2000)

Correspondence:

c1 Address for Correspondence: Dr Nicholas G. Martin, Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Post Office, Royal Brisbane Hospital, Brisbane QLD 4029, Australia.

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