The Transcription Factor Hepatocyte Nuclear Factor-6/Onecut-1 Controls the Expression of Its Paralog Onecut-3 in Developing Mouse Endoderm

Abstract

During development, the endoderm gives rise to several organs, including the pancreas and liver. This differentiation process requires spatial and temporal regulation of gene expression in the endoderm by a network of tissue-specific transcription factors whose elucidation is far from complete. These factors include the Onecut protein hepatocyte nuclear factor-6 (HNF-6), which controls pancreas and liver development as shown in our previous work on Hnf6 knock-out embryos. In mammals, HNF-6 has two paralogs, Onecut-2 (OC-2) and OC-3, whose patterns of expression in the adult overlap with that of HNF-6. In the present work, we examine the expression profile of the three Onecut factors in the developing mouse endoderm. We show that HNF-6, OC-2, and OC-3 are expressed sequentially, which defines new steps in endoderm differentiation. By analyzing Hnf6 knock-out embryos we find that HNF-6 is required for expression of the Oc3 gene in the endoderm. We show that OC-3 colocalizes with HNF-6 in the endoderm and in embryonic pancreas and liver. Based on transfection, chromatin immunoprecipitation, and whole embryo electroporation experiments, we demonstrate that HNF-6 can bind to and stimulate the expression of the Oc3 gene. This study identifies a regulatory cascade between two paralogous transcription factors, sheds new light on the interpretation of the Hnf6 knock-out phenotype, and broadens the transcription factors network operating during development of the endoderm, liver, and pancreas.

Transcription factor onecut3 regulates intrahepatic biliary development in zebrafish

“…Comparison of the onset of liver expression of hnf6 and oc3 demonstrated no difference in the timing of initiation of liver expression (data not shown). The timing and widespread expression of hnf6 and oc3 in the larval zebrafish liver suggest that both genes are expressed in hepatoblasts, as similarly reported for the mouse orthologs (Rausa et al, 1997;Clotman et al, 2002;Pierreux et al, 2004).…”

“…In mouse, Oc3 is expressed in developing brain, liver, stomach, proximal intestine, and pancreas, similar to the expression pattern of Hnf6 ( Vanhorenbeeck et al, 2002;Pierreux et al, 2004). The timing of expression, however, is different, with Hnf6 expression preceding Oc3 expression (Pierreux et al, 2004).…”

“…In mice, Onecut3 (Oc3) is the last in the sequence of onecut genes to be active in endodermal development, and its expression appears to be directly activated by Hnf6 (Pierreux et al, 2004). A role for Oc3 in biliary development, however, has not been reported.…”

“…The timing of expression, however, is different, with Hnf6 expression preceding Oc3 expression (Pierreux et al, 2004). We examined the expression of oc3 in developing zebrafish embryos and larvae by in situ hybridization.…”

Ngn3 expression during postnatal in vitro beta cell neogenesis induced by the JAK/STAT pathway

“…Madsen, Hagedorn Research Institute, Gentofte, Denmark), 38 polyclonal anti-Pdx1 (O.D. Madsen) 8 , polyclonal anti-Ngn3, 16 monoclonal anti-cytokeratin-20 (CK20) (Novocastra, Newcastle-upon-Tyne, UK), 36,37 monoclonal anti-b-catenin (BD Biosciences, Erembodegem, Belgium), 39 polyclonal anti-Hnf6 (Santa Cruz Biotechnology, CA, USA) 40 and polyclonal anti-lipase (Biodesign International, Maine, USA). Secondary antibodies conjugated with fluorescein isothiocyanate, tetramethylrodamine isothiocyanate or Cy5 (Jackson Immunoresearch, West Grove, PA) were used as described previously.…”