Abstract
When dietary choline is restricted, most men and postmenopausal women develop multiorgan dysfunction marked by hepatic steatosis (choline deficiency syndrome (CDS)). However, a significant subset of premenopausal women is protected from CDS. Because hepatic PEMT (phosphatidylethanolamine N-methyltransferase) catalyzes de novo biosynthesis of choline and this gene is under estrogenic control, we hypothesized that there are SNPs in PEMT that disrupt the hormonal regulation of PEMT and thereby put women at risk for CDS. In this study, we performed transcript-specific gene expression analysis, which revealed that estrogen regulates PEMT in an isoform-specific fashion. Locus-wide SNP analysis identified a risk-associated haplotype that was selectively associated with loss of hormonal activation. Chromatin immunoprecipitation, analyzed by locus-wide microarray studies, comprehensively identified regions of estrogen receptor binding in PEMT. The polymorphism (rs12325817) most highly linked with the development of CDS (p < 0.00006) was located within 1 kb of the critical estrogen response element. The risk allele failed to bind either the estrogen receptor or the pioneer factor FOXA1. These data demonstrate that allele-specific ablation of estrogen receptor-DNA interaction in the PEMT locus prevents hormone-inducible PEMT expression, conferring risk of CDS in women.
Highlights
Most men and postmenopausal women deprived of dietary choline, the majority (56%) of premenopausal women seem to be protected against choline deficiencyinduced syndrome (CDS) [1]
We examined a targeted set of single nucleotide polymorphism (SNP) in genes involved in choline metabolism and identified one SNP in PEMT that was highly associated with CDS in women [20]
HapMap data, other SNPs in this region were found to be in high linkage disequilibrium with rs4646343, including an SNP located in common exon 3 (Centre d’Etude du Polymorphisme Humain (CEPH); r2 ϭ 0.695)
Summary
Most men and postmenopausal women deprived of dietary choline, the majority (56%) of premenopausal women seem to be protected against CDS [1]. Using allele- and transcript-specific gene expression analyses, we identified the PEMT transcripts that were induced by estrogen and demonstrated that, in primary human hepatocytes, estrogen responsiveness was abrogated in the risk haploblock. For the transcript-specific gene expression analysis in human liver biopsies and the PEMT activity studies, statistical differences were assessed using an analysis of variance and TukeyKramer test.
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