Hepatocyte-specific deletion of hepatocyte nuclear factor-4α in adult mice results in increased hepatocyte proliferation

Abstract

Hepatocyte nuclear factor-4␣ (HNF4␣) is known as the master regulator of hepatocyte differentiation. Recent studies indicate that HNF4␣ may inhibit hepatocyte proliferation via mechanisms that have yet to be identified. Using a HNF4␣ knockdown mouse model based on delivery of inducible Cre recombinase via an adeno-associated virus 8 viral vector, we investigated the role of HNF4␣ in the regulation of hepatocyte proliferation. Hepatocyte-specific deletion of HNF4␣ resulted in increased hepatocyte proliferation. Global gene expression analysis showed that a majority of the downregulated genes were previously known HNF4␣ target genes involved in hepatic differentiation. Interestingly, Ն500 upregulated genes were associated with cell proliferation and cancer. Furthermore, we identified potential negative target genes of HNF4␣, many of which are involved in the stimulation of proliferation. Using chromatin immunoprecipitation analysis, we confirmed binding of HNF4␣ at three of these genes. Furthermore, overexpression of HNF4␣ in mouse hepatocellular carcinoma cells resulted in a decrease in promitogenic gene expression and cell cycle arrest. Taken together, these data indicate that, apart from its role in hepatocyte differentiation, HNF4␣ actively inhibits hepatocyte proliferation by repression of specific promitogenic genes. adeno-associated virus; Ect2; gene repression; hepatocyte proliferation; liver regeneration THE LIVER IS KNOWN for its exceptional capability to regenerate in response to surgical removal, as well as following druginduced liver injury. Liver regeneration is critical in maintaining liver health, because the liver is the major site of xenobiotic detoxification and is exposed to a variety of drugs and chemicals. The mechanisms of initiation and progression of liver regeneration are well studied, but the mechanisms of termination of regeneration are not completely understood (27). It is important to understand the mechanisms of termination of liver regeneration, because many of the pathways involved in stimulation of liver regeneration can be carcinogenic if left unchecked. It is known that the mechanisms of termination of regeneration are essential to maintain controlled liver growth and inhibit progression to hepatocellular carcinoma (HCC). However, the detailed mechanisms of termination of regeneration and their link to prevention of HCC are not completely clear.Hepatocyte nuclear factor-4␣ (HNF4␣, representative public ID NR2A1) is considered the master regulator of hepatocyte differentiation. It plays an important role in the regulation of many hepatocyte-specific genes, including those involved in glycolysis, gluconeogenesis, ureagenesis, fatty acid metabolism, bile acid synthesis, drug metabolism, apolipoprotein synthesis, and blood coagulation (11, 15, 18 -21). Recent studies suggest a novel role of HNF4␣ in the regulation of cell proliferation (8,9,11,12,15,23,26,29,36). Data indicate that HNF4␣ may have antiproliferative activity in human embryonic kidney cells and rat pancreatic beta cell...

Hepatitis C Virus Entry Is Impaired by Claudin-1 Downregulation in Diacylglycerol Acyltransferase-1-Deficient Cells

“…In DGAT1-silenced cells, we examined the expression of hepatocyte nuclear factor 4␣ (HNF4␣) because this factor has been reported to be associated with CLDN1 expression in mice (32)(33)(34). In fact, HNF4␣ expression was markedly reduced in DGAT1-silenced cell lines at both the mRNA and protein levels (Fig.…”

“…HNF4␣ is a central regulator of hepatocyte differentiation and function (33,34) and is a major transcription factor that regulates the expression of genes that are involved in lipid homeostasis (42). HNF4␣ is also known to regulate the expression of proteins that are required for hepatic and intestinal tight junction assembly, including CLDN1, in mice (30)(31)(32).…”

Advances in cholangiocarcinoma research: report from the third Cholangiocarcinoma Foundation Annual Conference

“…Specifically, he is focusing on potential interactions between the Wnt/β-catenin pathway and hepatocyte nuclear factor 4 alpha (HNF4α), molecules that are involved in the development of the liver as well as CCA (35)(36)(37)(38)(39)(40). Studies in the laboratory have shown that knockdown of HNF4α in the zebrafish leads to a reduction in hepatocyte differentiation while genetic or chemical increase in β-catenin results in a loss of HNF4α and a maintenance of cholangiocyte differentiation.…”

Differential Effects of Hepatocyte Nuclear Factor 4α Isoforms on Tumor Growth and T-Cell Factor 4/AP-1 Interactions in Human Colorectal Cancer Cells

“…P1-HNF4␣ acts as a tumor suppressor in the liver (24), inhibiting hepatocyte proliferation and inflammation (25)(26)(27). Several key players in proliferation, including p53, c-Myc, T-cell factor 4 (TCF4 [TCF7L2]), lymphoid enhancer factor 1 (LEF1 [LEF1]), and cyclin D1, have all been shown to physically interact with and antagonize P1-HNF4␣ (12,(28)(29)(30)(31)(32)(33).…”