Hepatocyte nuclear factor 4alpha, a key factor for homeostasis, cell architecture, and barrier function of the adult intestinal epithelium. Mol Cell Biol. 2009;29:6294-6308. [PMID: 19805521 DOI: 10.1128/mcb.00939-09]

Yersinia pseudotuberculosis disrupts intestinal barrier integrity through hematopoietic TLR-2 signaling

Intestinal barrier function requires intricate cooperation between intestinal epithelial cells and immune cells. Enteropathogens are able to invade the intestinal lymphoid tissue known as Peyer's patches (PPs) and disrupt the integrity of the intestinal barrier. However, the underlying molecular mechanisms of this process are poorly understood. In mice infected with Yersinia pseudotuberculosis, we found that PP barrier dysfunction is dependent on the Yersinia virulence plasmid and the expression of TLR-2 by hematopoietic cells, but not by intestinal epithelial cells. Upon TLR-2 stimulation, Y. pseudotuberculosis-infected monocytes activated caspase-1 and produced IL-1β. In turn, IL-1β increased NF-κB and myosin light chain kinase activation in intestinal epithelial cells, thus disrupting the intestinal barrier by opening the tight junctions. Therefore, Y. pseudotuberculosis subverts intestinal barrier function by altering the interplay between immune and epithelial cells during infection.

Amelioration of diabesity-induced colorectal ontogenesis by omega-3 fatty acids in mice

Postnatal intestinal ontogenesis in an animal model of diabesity may recapitulate morphological and transduction features of diabesity-induced intestinal dysplasia and its amelioration by endogenous (n-3) polyunsaturated fatty acids (PUFA). Proliferation, differentiation, and transduction aspects of intestinal ontogenesis have been studied here in obese, insulin-resistant db/db mice, in fat-1 transgene coding for desaturation of (n-6) PUFA into (n-3) PUFA, in db/db crossed with fat-1 mice, and in control mice. Diabesity resulted in increased colonic proliferation and dedifferentiation of epithelial colonocytes and goblet cells, with increased colonic β-catenin and hepatocyte nuclear factor (HNF)-4α transcriptional activities accompanied by enrichment in HNF-4α-bound (n-6) PUFA. In contrast, in fat-1 mice, colonic proliferation was restrained, accompanied by differentiation of crypt stem cells into epithelial colonocytes and goblet cells and by decrease in colonic β-catenin and HNF-4α transcriptional activities, with concomitant enrichment in HNF-4α-bound (n-3) PUFA at the expense of (n-6) PUFA. Colonic proliferation and differentiation, the profile of β-catenin and HNF-4α-responsive genes, and the composition of HNF-4α-bound PUFA of db/db mice reverted to wild-type by introducing the fat-1 gene into the db/db context. Suppression of intestinal HNF-4α activity by (n-3) PUFA may ameliorate diabesity-induced intestinal ontogenesis and offer an effective preventive modality for colorectal cancer.

An HNF4α-miRNA inflammatory feedback circuit regulates hepatocellular oncogenesis

Hepatocyte nuclear factor 4α (HNF4α) is essential for liver development and hepatocyte function. Here, we show that transient inhibition of HNF4α initiates hepatocellular transformation through a microRNA-inflammatory feedback loop circuit consisting of miR-124, IL6R, STAT3, miR-24, and miR-629. Moreover, we show that, once this circuit is activated, it maintains suppression of HNF4α and sustains oncogenesis. Systemic administration of miR-124, which modulates inflammatory signaling, prevents and suppresses hepatocellular carcinogenesis by inducing tumor-specific apoptosis without toxic side effects. As we also show that this HNF4α circuit is perturbed in human hepatocellular carcinomas, our data raise the possibility that manipulation of this microRNA feedback-inflammatory loop has therapeutic potential for treating liver cancer.

Current and emerging approaches to define intestinal epithelium-specific transcriptional networks

Upon developmental or environmental cues, the composition of transcription factors in a transcriptional regulatory network is deeply implicated in controlling the signature of the gene expression and thereby specifies the cell or tissue type. Novel methods including ChIP-chip and ChIP-Seq have been applied to analyze known transcription factors and their interacting regulatory DNA elements in the intestine. The intestine is an example of a dynamic tissue where stem cells in the crypt proliferate and undergo a differentiation process toward the villus. During this differentiation process, specific regulatory networks of transcription factors are activated to target specific genes, which determine the intestinal cell fate. The expanding genomewide mapping of transcription factor binding sites and construction of transcriptional regulatory networks provide new insight into how intestinal differentiation occurs. This review summarizes the current overview of the transcriptional regulatory networks driving epithelial differentiation in adult intestine. The novel technologies that have been implied to study these networks are presented and their prospects for implications in future research are also addressed.

Src tyrosine kinase phosphorylation of nuclear receptor HNF4α correlates with isoform-specific loss of HNF4α in human colon cancer

Src tyrosine kinase has long been implicated in colon cancer but much remains to be learned about its substrates. The nuclear receptor hepatocyte nuclear factor 4α (HNF4α) has just recently been implicated in colon cancer but its role is poorly defined. Here we show that c-Src phosphorylates human HNF4α on three tyrosines in an interdependent and isoform-specific fashion. The initial phosphorylation site is a Tyr residue (Y14) present in the N-terminal A/B domain of P1- but not P2-driven HNF4α. Phospho-Y14 interacts with the Src SH2 domain, leading to the phosphorylation of two additional tyrosines in the ligand binding domain (LBD) in P1-HNF4α. Phosphomimetic mutants in the LBD decrease P1-HNF4α protein stability, nuclear localization and transactivation function. Immunohistochemical analysis of approximately 450 human colon cancer specimens (Stage III) reveals that P1-HNF4α is either lost or localized in the cytoplasm in approximately 80% of tumors, and that staining for active Src correlates with those events in a subset of samples. Finally, three SNPs in the human HNF4α protein, two of which are in the HNF4α F domain that interacts with the Src SH3 domain, increase phosphorylation by Src and decrease HNF4α protein stability and function, suggesting that individuals with those variants may be more susceptible to Src-mediated effects. This newly identified interaction between Src kinase and HNF4α has important implications for colon and other cancers.

Molecular mechanisms of Barrett's esophagus

Barrett's esophagus (BE) is defined as the metaplastic conversion of esophageal squamous epithelium to intestinalized columnar epithelium. As a premalignant lesion of esophageal adenocarcinoma (EAC), BE develops as a result of chronic gastroesophageal reflux disease (GERD). Many studies have been conducted to understand the molecular mechanisms of this disease. This review summarizes recent results involving squamous and intestinal transcription factors, signaling pathways, stromal factors, microRNAs, and other factors in the development of BE. A conceptual framework is proposed to guide future studies. We expect elucidation of the molecular mechanisms of BE to help in the development of improved management of GERD, BE, and EAC.

Nuclear receptor HNF4α binding sequences are widespread in Alu repeats

Background

Alu repeats, which account for ~10% of the human genome, were originally considered to be junk DNA. Recent studies, however, suggest that they may contain transcription factor binding sites and hence possibly play a role in regulating gene expression.

Results

Here, we show that binding sites for a highly conserved member of the nuclear receptor superfamily of ligand-dependent transcription factors, hepatocyte nuclear factor 4alpha (HNF4α, NR2A1), are highly prevalent in Alu repeats. We employ high throughput protein binding microarrays (PBMs) to show that HNF4α binds > 66 unique sequences in Alu repeats that are present in ~1.2 million locations in the human genome. We use chromatin immunoprecipitation (ChIP) to demonstrate that HNF4α binds Alu elements in the promoters of target genes (ABCC3, APOA4, APOM, ATPIF1, CANX, FEMT1A, GSTM4, IL32, IP6K2, PRLR, PRODH2, SOCS2, TTR) and luciferase assays to show that at least some of those Alu elements can modulate HNF4α-mediated transactivation in vivo (APOM, PRODH2, TTR, APOA4). HNF4α-Alu elements are enriched in promoters of genes involved in RNA processing and a sizeable fraction are in regions of accessible chromatin. Comparative genomics analysis suggests that there may have been a gain in HNF4α binding sites in Alu elements during evolution and that non Alu repeats, such as Tiggers, also contain HNF4α sites.

Conclusions

Our findings suggest that HNF4α, in addition to regulating gene expression via high affinity binding sites, may also modulate transcription via low affinity sites in Alu repeats.

Association of FCGR2A, JAK2 or HNF4A variants with ulcerative colitis in Koreans

BACKGROUND

Recent genome-wide association studies have identified over 40 candidate genes contributing to ulcerative colitis susceptibility. The goal of this study was to test the reported ulcerative colitis susceptibility genes including FCGR2A, SLC26A3, JAK2 and HNF4A in Korean patients with ulcerative colitis and Crohn's disease.

METHODS

Five single nucleotide polymorphisms from 4 loci including FCGR2A, SLC26A3, JAK2 and HNF4A were genotyped in 661 patients with ulcerative colitis, 642 patients with Crohn's disease and 601 healthy controls.

RESULTS

Statistically significant associations with ulcerative colitis were found at FCGR2A (rs1801274, p=2.3×10(-4), OR=0.70 (95% CI=0.57-0.84) under the allelic model), the JAK2 locus (rs10975003, p=6.7×10(-4), OR=1.43 (95% CI=1.16-1.77) under the allelic model) and HNF4A (rs6017342, p=0.002, OR=0.66 (95% CI=0.51-0.85) under the allelic model). The association of FCGR2A was much stronger in female patients with ulcerative colitis (p=5.7×10(-6)) than in males (p=0.50). Except rs10975003 from the JAK2 locus, none showed positive association with Crohn's disease.

CONCLUSIONS

Our data suggest that FCGR2A, JAK2 or HNF4A variants play a role in the pathogenesis of ulcerative colitis in Koreans.

Intestinal development and differentiation

In this review, we present an overview of intestinal development and cellular differentiation of the intestinal epithelium. The review is separated into two sections: Section one summarizes organogenesis of the small and large intestines, including endoderm and gut tube formation in early embryogenesis, villus morphogenesis, and crypt formation. Section two reviews cell fate specification and differentiation of each cell type within the intestinal epithelium. Growth factor and transcriptional networks that regulate these developmental processes are summarized.

Hepatocyte nuclear factor (HNF) 4α expression distinguishes ampullary cancer subtypes and prognosis after resection

OBJECTIVE

To investigate biological differences and prognostic indicators of different ampullary cancer (AC) subtypes.

BACKGROUND

AC is associated with a favorable prognosis compared with other periampullary carcinomas. Aside from other prognostic factors, the histological origin of AC may determine survival. Specifically, the pancreatobiliary subtype of AC displays worse prognosis compared with the intestinal subtype. However, knowledge of inherent molecular characteristics of different periampullary tumors and their effects on prognosis has been limited.

METHODS

Gene expression profiling was used to screen for differential gene expression between 6 PDAC cases and 12 AC cases. Among others, hepatocyte nuclear factor 4α (HNF4α) mRNA overexpression was observed in AC cases. Nuclear HNF4α protein expression was assessed using tissue microarrays consisting of 99 individual AC samples. The correlation of HNF4α expression with clinicopathological data (n = 99) and survival (n = 84) was assessed.

RESULTS

HNF4α mRNA is 7.61-fold up-regulated in AC compared with that in PDAC. Bioinformatics analyses indicated its key role in dysregulated signaling pathways. Nuclear HNF4α expression correlates with histological subtype, grading, CDX2 positivity, MUC1 negativity and presence of adenomatous components in the carcinoma. The presence of HNF4α is a univariate predictor of survival in AC mean survival (50 months versus 119 months, P = 0.002). Multivariate analysis revealed that HNF4α negativity (HR = 17.95, 95% CI: 2.35-136.93, P = 0.005) and lymph node positivity (HR = 3.33, 95% CI: 1.36-8.18, P = 0.009) are independent negative predictors of survival.

CONCLUSIONS

Immunohistochemical determination of HNF4α expression is an effective tool for distinguishing different AC subtypes. Similarly, HNF4α protein expression is an independent predictor of favorable prognosis in carcinoma of the papilla of Vater and may serve for risk stratification after curative resection.

HNF4α and CDH1 are associated with ulcerative colitis in a Dutch cohort

BACKGROUND

Inflammatory bowel diseases (IBDs), consisting of ulcerative colitis (UC) and Crohn's disease (CD), are complex disorders with multiple genes contributing to disease pathogenesis. A recent genome-wide association scan identified three novel susceptibility loci for UC: HNF4α, CDH1, and LAMB1. We performed an analysis of these three loci in an independent cohort.

METHODS

In all, 821 UC patients and 1260 healthy controls of central European Caucasian descent were genotyped for single nucleotide polymorphisms (SNPs): rs6017342 (HNF4α), rs1728785 (CDH1), and rs6949033 (LAMB1). Differences in allele and genotype distribution in cases and controls were tested for significance with the χ² test.

RESULTS

Allelic association analysis showed that SNP rs6017342 in the HNF4α locus was strongly associated with UC (P = 1,04 × 10(-11) , odds ratio [OR] = 1.56, 95% confidence interval [CI] = 1.37-1.77) and SNP rs1728785 (CDH1) was associated with P = 0.01 (OR = 1.23, 95% CI = 1.05-1.44). SNP rs6949033 in LAMB1 was not associated in our cohort (P = 0.12, OR = 1.11, 95% CI = 0.97-1.26). We found an association for SNP rs6949033 (LAMB1) for disease limited to the rectum (P = 0.02). However, this association was lost after correcting for multiple testing. No further specific subphenotype associations were identified.

CONCLUSIONS

This is the first independent study to replicate the HNF4α and CDH1 loci as susceptibility loci for UC. The main candidate genes in these risk loci play important roles in the maintenance of the integrity of the epithelial barrier, highlighting the importance of the mucosal barrier function for UC pathogenesis.

Genetics and pathogenesis of inflammatory bowel disease

Recent advances have provided substantial insight into the maintenance of mucosal immunity and the pathogenesis of inflammatory bowel disease. Cellular programs responsible for intestinal homeostasis use diverse intracellular and intercellular networks to promote immune tolerance, inflammation or epithelial restitution. Complex interfaces integrate local host and microbial signals to activate appropriate effector programs selectively and even drive plasticity between these programs. In addition, genetic studies and mouse models have emphasized the role of genetic predispositions and how they affect interactions with microbial and environmental factors, leading to pro-colitogenic perturbations of the host-commensal relationship.

Genetics and pathogenesis of inflammatory bowel disease

Recent advances have provided substantial insight into the maintenance of mucosal immunity and the pathogenesis of inflammatory bowel disease. Cellular programs responsible for intestinal homeostasis use diverse intracellular and intercellular networks to promote immune tolerance, inflammation or epithelial restitution. Complex interfaces integrate local host and microbial signals to activate appropriate effector programs selectively and even drive plasticity between these programs. In addition, genetic studies and mouse models have emphasized the role of genetic predispositions and how they affect interactions with microbial and environmental factors, leading to pro-colitogenic perturbations of the host-commensal relationship.

Hepatocyte nuclear factor 4α gene mutation associated with familial neonatal hyperinsulinism and maturity-onset diabetes of the young

Neonatal macrosomia and hyperinsulinemic hypoglycemia with strong family history of diabetes may indicate monogenic diabetes. Here we report a family in which 4 individuals in 3 generations were found to have a mutation (Arg80Gln) in hepatocyte nuclear factor 4α. Genetic testing was a factor in choosing sulfonylurea therapy for diabetes.

Genetics of ulcerative colitis

Ulcerative colitis (UC) and Crohn's disease (CD) are related polygenic inflammatory bowel diseases (IBDs), with distinct and overlapping susceptibility loci. Recently, hypothesis-free genome-wide association (GWA) studies have revolutionized the field of complex disease genetics. Substantial advances have been achieved in defining the genetic architecture of IBD. To date, over 60 published IBD susceptibility loci have been discovered and replicated, of which approximately a third are associated with both UC and CD, although 21 are specific to UC and 23 to CD. In CD, the breakthrough identification of NOD2 as a susceptibility gene was followed by a rapid phase of gene discovery from GWA studies between 2006 and 2008. Progress in UC was slower; however, by initially testing hits for CD in UC, and later scanning larger UC cohorts, significant new loci for UC have been discovered, with exciting novel insights into disease pathogenesis. Notably, genes implicated in mucosal barrier function (ECM1, CDH1, HNF4α, and laminin B1) confer risk of UC; furthermore, E-cadherin is the first genetic correlation between colorectal cancer and UC. Impaired IL10 signaling has reemerged as a key pathway in intestinal inflammation, and is perhaps the most amenable to therapeutic intervention in UC. Collaborative international efforts with large meta-analyses of GWA studies and replication will yield many new UC genes. Furthermore, a large effort is required to characterize the loci found. Fine-mapping, deep resequencing, and functional studies will be critical to translating these gene discoveries into pathogenic insights, and ultimately into clinical insights and novel therapeutics.

Vertebrate intestinal endoderm development

The endoderm gives rise to the lining of the esophagus, stomach and intestines, as well as associated organs. To generate a functional intestine, a series of highly orchestrated developmental processes must occur. In this review, we attempt to cover major events during intestinal development from gastrulation to birth, including endoderm formation, gut tube growth and patterning, intestinal morphogenesis, epithelial reorganization, villus emergence, as well as proliferation and cytodifferentiation. Our discussion includes morphological and anatomical changes during intestinal development as well as molecular mechanisms regulating these processes.

Hepatocyte nuclear factor-4alpha promotes gut neoplasia in mice and protects against the production of reactive oxygen species

Hepatocyte nuclear factor-4α (Hnf4α) is a transcription factor that controls epithelial cell polarity and morphogenesis. Hnf4α conditional deletion during postnatal development has minor effects on intestinal epithelium integrity but promotes activation of the Wnt/β-catenin pathway without causing tumorigenesis. Here, we show that Hnf4α does not act as a tumor-suppressor gene but is crucial in promoting gut tumorigenesis in mice. Polyp multiplicity in ApcMin mice lacking Hnf4α is suppressed compared with littermate ApcMin controls. Analysis of microarray gene expression profiles from mice lacking Hnf4α in the intestinal epithelium identifies novel functions of this transcription factor in targeting oxidoreductase-related genes involved in the regulation of reactive oxygen species (ROS) levels. This role is supported with the demonstration that HNF4α is functionally involved in the protection against spontaneous and 5-fluorouracil chemotherapy-induced production of ROS in colorectal cancer cell lines. Analysis of a colorectal cancer patient cohort establishes that HNF4α is significantly upregulated compared with adjacent normal epithelial resections. Several genes involved in ROS neutralization are also induced in correlation with HNF4A expression. Altogether, the findings point to the nuclear receptor HNF4α as a potential therapeutic target to eradicate aberrant epithelial cell resistance to ROS production during intestinal tumorigenesis.