Australasian Microarray & Associated Technologies Association, AMATA

Jeffrey M Craig, Lavinia Gordon, Gordon Smyth, Eric Joo, Roberta Andronikos, Alicia Oshlak, John. Carlin, Ruth Morley, R. Saffery.

Monozygotic(‘identical’) twins, originating from a single zygote, are considered to begenetically identical. Genetic identity does not, however, imply phenotypicidentity. Recently, there has been an increasing focus on epigenetic differences as a source of phenotypic discordance within monozygotic twin pairs. Most epigenetic marks are erased from the genome after fertilisation, with re-establishment occurring early in embryonic development and evidence suggests that the prenatal period involves epigenetic remodelling on a scale unparalleled postnatally. We hypothesise that that the prenatal epigenetically-driven developmental program is plastic and can vary from the norm via random and microenvironment-driven epigenetic change, and as a result, that epigenetic divergence can be identified in monozygotic at birth. This study forms part of a larger study – PETS; the Peri/postnatal Epigenetic Twins Study - investigating epigenetic variation and its association with birth weight discordance, maternal nutrition and foetal genotype in a newly-established cohort of 250 mothers and twin pairs. Specifically, this study aims to identify gene expression and methylation differences within newborn monozygotic twin pairs, in multiple cell types, and to relate these to phenotypic discordance. This presentation will focus on preliminary results obtained from genome-wide expression profiling of cord blood mononuclear cells and umbilical cord vein endothelial cells (HUVECs) from monozygotic twin pairs, both concordant and discordant for birth weight, using Illumina Human-6Beadchips.