The effect of alcohol on the methylation status of the imprinting control regions contained within three developmentally significant loci
Date
2010-02-25T10:37:47Z
Authors
Knezovich, Jaysen Gregory
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Abstract
Imprinted loci are critical in foetal development and most are regulated by the
methylation-specific CTCF binding protein which binds imprinting control regions
(ICRs). The ICR is located between two genes that comprise imprinted loci, which are
reciprocally expressed in a parent-of-origin specific manner. Maternally
hypomethylated ICRs allow CTCF binding, creating a boundary element which
prevents downstream enhancers from acting on the paternally expressed gene
upstream of the ICR. Conversely, the hypermethylated (imprinted) paternal ICR
prevents CTCF binding, allowing downstream enhancers to act on the gene upstream
of the ICR, while suppressing the downstream maternally expressed gene. Alcohol
and its metabolites are able to reach the testes via the blood supply and are known
to reduce global DNA methylation by disrupting the folate, methyl group and
homocysteine pathway. This may therefore affect gene expression at imprinted loci,
whose parental alleles are discriminated by the imprinting status at the ICR.
The effect of pre-conception paternal alcohol exposure on the DNA methylation of
three paternally imprinted ICRs (H19, Rasgrf1, IG-DMR) as well as the maternally
imprinted Snrpn ICR was examined in mouse sperm and their offspring. Male mice
were gavaged with ethanol or sucrose. DNA was extracted from sperm of treated
males and tail biopsies from offspring. Samples were bisulphite modified and the ICRs
PCR amplified. DNA methylation patterns of ICRs were analysed by sequencing and
quantitatively via pyrosequencing. Sperm samples of ethanol treated males did not
show significant demethylation when compared to sucrose treated mice, with the
exception of H19 CpG 7, Rasgrf1 CpG 26 and Snrpn CpG 10 (p=0.024, 0.014 and
Description
MSc(Med), Human Genetics, Faculty of Health Sciences, University of the Witwatersrand, 2009
Keywords
alcohol, DNA methylation