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Molecular and Cellular Biology, February 2001, p. 1393-1403, Vol. 21, No. 4
Laboratory of Metabolism, Division of Basic
Sciences, National Cancer Institute,1 and
Metabolic Disease Branch, National Heart, Lung and Blood
Institute,2 National Institutes of Health,
Bethesda, Maryland 20892, and Office of Laboratory Animal
Resources, National Cancer Institute, National Institutes of
Health, Frederick, Maryland 217023
Received 5 July 2000/Returned for modification 29 August
2000/Accepted 31 October 2000
The numerous functions of the liver are controlled primarily at the
transcriptional level by the concerted actions of a limited number of
hepatocyte-enriched transcription factors (hepatocyte nuclear factor
1
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.4.1393-1403.2001
Hepatocyte Nuclear Factor 4
(Nuclear Receptor
2A1) Is Essential for Maintenance of Hepatic Gene Expression
and Lipid Homeostasis

[HNF1
], -1
, -3
, -3
, -3
, -4
, and -6 and members
of the c/ebp family). Of these, only HNF4
(nuclear receptor 2A1) and
HNF1
appear to be correlated with the differentiated phenotype of
cultured hepatoma cells. HNF1
-null mice are viable, indicating that
this factor is not an absolute requirement for the formation of an
active hepatic parenchyma. In contrast, HNF4
-null mice die during
embryogenesis. Moreover, recent in vitro experiments using tetraploid
aggregation suggest that HNF4
is indispensable for hepatocyte
differentiation. However, the function of HNF4
in the maintenance of
hepatocyte differentiation and function is less well understood. To
address the function of HNF4
in the mature hepatocyte, a conditional
gene knockout was produced using the Cre-loxP system. Mice lacking
hepatic HNF4
expression accumulated lipid in the liver and exhibited
greatly reduced serum cholesterol and triglyceride levels and increased
serum bile acid concentrations. The observed phenotypes may be
explained by (i) a selective disruption of very-low-density lipoprotein
secretion due to decreased expression of genes encoding apolipoprotein
B and microsomal triglyceride transfer protein, (ii) an increase in
hepatic cholesterol uptake due to increased expression of the major
high-density lipoprotein receptor, scavenger receptor BI, and (iii) a
decrease in bile acid uptake to the liver due to down-regulation of the
major basolateral bile acid transporters sodium taurocholate
cotransporter protein and organic anion transporter protein 1. These
data indicate that HNF4
is central to the maintenance of hepatocyte
differentiation and is a major in vivo regulator of genes involved in
the control of lipid homeostasis.
*
Corresponding author. Mailing address: Building 37, Room 3E-24, National Institutes of Health, Bethesda, MD 20892. Phone: (301) 496-9067. Fax: (301) 496-8419. E-mail:
fjgonz{at}helix.nih.gov.
Present address: Institute of Molecular Biology, Academia Sinica,
Taipei 115, Taiwan.
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