HNF-1 alpha and HNF-1 beta expression in mouse intestinal crypts.

Hepatocyte nuclear factors 1 alpha and 1 beta (HNF-1 alpha and HNF-1 beta) are homologous homeodomain-containing transcription factors that form homodimers or heterodimers that bind the same consensus sequence in the promoters of several genes expressed in liver. Many of these genes, including the mouse alpha-fetoprotein (AFP) gene, are also expressed in the intestinal epithelium. AFP expression is restricted to the enteroendocrine cell lineage in the adult small intestine, and we have investigated the distribution of HNF-1 alpha and HNF-1 beta mRNA in the mouse intestine to determine whether expression of either of these regulatory factors colocalizes with AFP. We found that transcripts encoding both factors are expressed at the highest levels in crypts of small and large intestine. Quantitation shows that the relative ratio of HNF-1 alpha to HNF-1 beta mRNAs appears lower in the colon, where AFP is not expressed. Alterations in the ratio of HNF-1 alpha to HNF-1 beta along the length of the intestine may influence HNF-1 dimer formation and expression of target genes. Although HNF-1 is necessary for transcription of the AFP gene, other factors must be involved in eliciting the cell type-specific pattern of AFP expression in the intestine.