Sexually dimorphic genome-wide binding of retinoid X receptor alpha (RXRα) determines male-female differences in the expression of hepatic lipid processing genes in mice

PLoS One. 2013 Aug 19;8(8):e71538. doi: 10.1371/journal.pone.0071538. eCollection 2013.

Abstract

Many hepatic functions including lipid metabolism, drug metabolism, and inflammatory responses are regulated in a sex-specific manner due to distinct patterns of hepatic gene expression between males and females. Regulation for the majority of these genes is under control of Nuclear Receptors (NRs). Retinoid X Receptor alpha (RXRα) is an obligate partner for multiple NRs and considered a master regulator of hepatic gene expression, yet the full extent of RXRα chromatin binding in male and female livers is unclear. ChIP-Seq analysis of RXRα and RNA Polymerase2 (Pol2) binding was performed livers of both genders and combined with microarray analysis. Mice were gavage-fed with the RXR ligand LG268 for 5 days (30 mg/kg/day) and RXRα-binding and RNA levels were determined by ChIP-qPCR and qPCR, respectively. ChIP-Seq revealed 47,845 (male) and 46,877 (female) RXRα binding sites (BS), associated with ∼12,700 unique genes in livers of both genders, with 91% shared between sexes. RXRα-binding showed significant enrichment for 2227 and 1498 unique genes in male and female livers, respectively. Correlating RXRα binding strength with Pol2-binding revealed 44 genes being male-dominant and 43 female-dominant, many previously unknown to be sexually-dimorphic. Surprisingly, genes fundamental to lipid metabolism, including Scd1, Fasn, Elovl6, and Pnpla3-implicated in Fatty Liver Disease pathogenesis, were predominant in females. RXRα activation using LG268 confirmed RXRα-binding was 2-3 fold increased in female livers at multiple newly identified RXRα BS including for Pnpla3 and Elovl6, with corresponding ∼10-fold and ∼2-fold increases in Pnpla3 and Elovl6 RNA respectively in LG268-treated female livers, supporting a role for RXRα regulation of sexually-dimorphic responses for these genes. RXRα appears to be one of the most widely distributed transcriptional regulators in mouse liver and is engaged in determining sexually-dimorphic expression of key lipid-processing genes, suggesting novel gender- and gene-specific responses to NR-based treatments for lipid-related liver diseases.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Binding Sites
  • Chromatin / metabolism
  • Chromatin Immunoprecipitation
  • Female
  • Gene Expression Regulation* / drug effects
  • Gene Ontology
  • Genome / genetics*
  • Lipid Metabolism / drug effects
  • Lipid Metabolism / genetics*
  • Liver / drug effects
  • Liver / metabolism*
  • Male
  • Mice
  • Organic Chemicals / pharmacology
  • Protein Binding / drug effects
  • Protein Binding / genetics
  • RNA Polymerase II / metabolism
  • Retinoid X Receptor alpha / agonists
  • Retinoid X Receptor alpha / metabolism*
  • Sex Characteristics*
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • Transcription Initiation Site

Substances

  • Chromatin
  • LG 268
  • Organic Chemicals
  • Retinoid X Receptor alpha
  • RNA Polymerase II