Hepatocyte nuclear factor 4α is required for cell differentiation and homeostasis in the adult mouse gastric epithelium

Am J Physiol Gastrointest Liver Physiol. 2016 Aug 1;311(2):G267-75. doi: 10.1152/ajpgi.00195.2016. Epub 2016 Jun 23.

Abstract

We have previously shown that the sequential transcription factors Xbp1→Mist1 (Bhlha15) govern the ultrastructural maturation of the secretory apparatus in enzyme-secreting zymogenic chief cells (ZCs) in the gastric unit. Here we sought to identify transcriptional regulators upstream of X-box binding protein 1 (XBP1) and MIST1. We used immunohistochemistry to characterize Hnf4α(flox/flox) adult mouse stomachs after tamoxifen-induced deletion of Hnf4α We used qRT-PCR, Western blotting, and chromatin immunoprecipitation to define the molecular interaction between hepatocyte nuclear factor 4 alpha (HNF4α) and Xbp1 in mouse stomach and human gastric cells. We show that HNF4α protein is expressed in pit (foveolar) cells, mucous neck cells, and zymogenic chief cells (ZCs) of the corpus gastric unit. Loss of HNF4α in adult mouse stomach led to reduced ZC size and ER content, phenocopying previously characterized effects of Xbp1 deletion. However, HNF4α(Δ/Δ) stomachs also exhibited additional phenotypes including increased proliferation in the isthmal stem cell zone and altered mucous neck cell migration, indicating a role of HNF4α in progenitor cells as well as in ZCs. HNF4α directly occupies the Xbp1 promoter locus in mouse stomach, and forced HNF4α expression increased abundance of XBP1 mRNA in human gastric cancer cells. Finally, as expected, loss of HNF4α caused decreased Xbp1 and Mist1 expression in mouse stomachs. We show that HNF4α regulates homeostatic proliferation in the gastric epithelium and is both necessary and sufficient for the upstream regulation of the Xbp1→Mist1 axis in maintenance of ZC secretory architecture.

Keywords: mucous neck cell; scaling factor; secretory cells.

MeSH terms

  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Binding Sites
  • Cell Differentiation*
  • Cell Line
  • Cell Proliferation*
  • Epithelial Cells / metabolism*
  • Epithelial Cells / pathology
  • Gastric Mucosa / metabolism*
  • Gastric Mucosa / pathology
  • Gene Expression Regulation
  • Genotype
  • Hepatocyte Nuclear Factor 4 / deficiency
  • Hepatocyte Nuclear Factor 4 / genetics
  • Hepatocyte Nuclear Factor 4 / metabolism*
  • Homeostasis
  • Humans
  • Mice, Knockout
  • Phenotype
  • Promoter Regions, Genetic
  • Signal Transduction
  • Transfection
  • X-Box Binding Protein 1 / genetics
  • X-Box Binding Protein 1 / metabolism

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • Bhlha15 protein, mouse
  • HNF4A protein, human
  • Hepatocyte Nuclear Factor 4
  • Hnf4a protein, mouse
  • X-Box Binding Protein 1
  • XBP1 protein, human
  • Xbp1 protein, mouse