Cellular differentiation is associated with transcriptional induction of distinct sets of tissue-specific genes whose expression is required for organ function. Deciphering the mechanisms that control tissue-specific transcription is, thus, critical to understanding cellular differentiation. We have utilized the transthyretin (TTR) DNA regulatory regions as a model in seeking to understand hepatocyte-specific gene transcription. Studies of the TTR promoter suggest that hepatocyte- specific gene regulation relies on combinatorial interaction of multiple DNA binding sites by several distinct families of hepatocyte nuclear factors (HNF). One of these regulatory proteins is the winged helix HNF- 3beta in regulating these genes remains unknown, because homozygous null HNF3beta mice die in utero prior to liver formation. The in vivo role of HNF-3beta in regulating these genes remains unknown, however, because homozygous null HNF-3beta mice die in utero prior to liver formation. In order to examine the regulatory function of HNF-3beta, we inhibited its activity in transgenic mice by increasing hepatocyte expression of the HNF-3beta protein, thus generating a mouse model of liver disease. The mice also display significant reductions in liver glycogen storage and increases in serum bile acid levels. We propose to use them to identify HNF-3beta genes whose altered expression is responsible for this liver phenotype. We recently cloned a Cut-Homeodomain transcription factor, HNF-6, which significantly enhances HNF-3beta and TTR promoter expression. Embryonic expression studies demonstrate that HNF-6 is first expressed in the murine hepatic diverticulum at the onset of liver organogenesis. Although the expression pattern of Hnf-6 and it potential target genes suggest that HNF-6 plays an important role in the induction of liver morphogenesis and hepatocyte differentiation, the exact nature of that role remains unknown. A mouse Hnf6 gene replacement targeting vector will be use to disrupt the murine gene by homologous recombination in embryonic stem (ES) cells, which will then be used to create homozygous null Hnf6 mice. We will use the Hnf6 deficient mice to test the hypothesis that HNF-6 expression is required for liver morphogenesis, hepatocyte differentiation and inn vivo target gene expression. Analysis of the phenotypes in these mice may provide information regarding human birth defects and liver disease resulting from altered expression of differentiating transcription factors.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM043241-11
Application #
6179669
Study Section
Metabolic Pathology Study Section (MEP)
Program Officer
Anderson, James J
Project Start
1990-07-01
Project End
2003-06-30
Budget Start
2000-07-01
Budget End
2001-06-30
Support Year
11
Fiscal Year
2000
Total Cost
$287,636
Indirect Cost
Name
University of Illinois at Chicago
Department
Biochemistry
Type
Schools of Medicine
DUNS #
121911077
City
Chicago
State
IL
Country
United States
Zip Code
60612
Tan, Yongjun; Yoshida, Yuichi; Hughes, Douglas E et al. (2006) Increased expression of hepatocyte nuclear factor 6 stimulates hepatocyte proliferation during mouse liver regeneration. Gastroenterology 130:1283-300
Yoshida, Yuichi; Hughes, Douglas E; Rausa 3rd, Francisco M et al. (2006) C/EBPalpha and HNF6 protein complex formation stimulates HNF6-dependent transcription by CBP coactivator recruitment in HepG2 cells. Hepatology 43:276-86
Costa, Robert H; Kalinichenko, Vladimir V; Major, Michael L et al. (2005) New and unexpected: forkhead meets ARF. Curr Opin Genet Dev 15:42-8
Wang, Minhua; Tan, Yongjun; Costa, Robert H et al. (2004) In vivo regulation of murine CYP7A1 by HNF-6: a novel mechanism for diminished CYP7A1 expression in biliary obstruction. Hepatology 40:600-8
Rausa 3rd, Francisco M; Hughes, Douglas E; Costa, Robert H (2004) Stability of the hepatocyte nuclear factor 6 transcription factor requires acetylation by the CREB-binding protein coactivator. J Biol Chem 279:43070-6
Sheng, Wanyun; Yan, Hong; Rausa 3rd, Francisco M et al. (2004) Structure of the hepatocyte nuclear factor 6alpha and its interaction with DNA. J Biol Chem 279:33928-36
Rausa, Francisco M; Tan, Yongjun; Costa, Robert H (2003) Association between hepatocyte nuclear factor 6 (HNF-6) and FoxA2 DNA binding domains stimulates FoxA2 transcriptional activity but inhibits HNF-6 DNA binding. Mol Cell Biol 23:437-49
Costa, Robert H; Kalinichenko, Vladimir V; Holterman, Ai-Xuan L et al. (2003) Transcription factors in liver development, differentiation, and regeneration. Hepatology 38:1331-47
Hughes, Douglas E; Stolz, Donna Beer; Yu, Songtao et al. (2003) Elevated hepatocyte levels of the Forkhead box A2 (HNF-3beta) transcription factor cause postnatal steatosis and mitochondrial damage. Hepatology 37:1414-24
Guo, Ying; Costa, Robert; Ramsey, Heather et al. (2002) The embryonic stem cell transcription factors Oct-4 and FoxD3 interact to regulate endodermal-specific promoter expression. Proc Natl Acad Sci U S A 99:3663-7

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