HNF-1-ALPHA AND HNF-1-BETA EXPRESSION IN MOUSE INTESTINAL CRYPTS

HepatocYte nuclear factors 1alpha and 1beta (HNF-1alpha and HNF-1beta) are homologous homeodomain-containing transcription factors that form homodimers or heterodimers that bind the same consensus sequence in t he 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 ente roendocrine cell lineage in the adult small intestine, and we have inv estigated the distribution of HNF-1alpha and HNF-1beta mRNA in the mou se intestine to determine whether expression of either of these regula tory factors colocalizes with AFP. We found that transcripts encoding both factors are expressed at the highest levels in crypts of small an d large intestine. Quantitation shows that the relative ratio of HNF-1 alpha to HNF-1beta mRNAs appears lower in the colon, where AFP is not expressed. Alterations in the ratio of HNF-1alpha to HNF-1beta along t he length of the intestine may influence HNF-1 dimer formation and exp ression 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.