Cooperation between HNF-1alpha, Cdx2, and GATA-4 in initiating an enterocytic differentiation program in a normal human intestinal epithelial progenitor cell line

GATA4 Forms a Positive Feedback Loop with CDX2 to Transactivate MUC2 in Bile Acids-Induced Gastric Intestinal Metaplasia

Background/Aims

Gastric intestinal metaplasia (GIM), a common precancerous lesion of gastric cancer, can be caused by bile acid reflux. GATA binding protein 4 (GATA4) is an intestinal transcription factor involved in the progression of gastric cancer. However, the expression and regulation of GATA4 in GIM has not been clarified.

Methods

The expression of GATA4 in bile acid-induced cell models and human specimens was examined. The transcriptional regulation of GATA4 was investigated by chromatin immunoprecipitation and luciferase reporter gene analysis. An animal model of duodenogastric reflux was used to confirm the regulation of GATA4 and its target genes by bile acids.

Results

GATA4 expression was elevated in bile acid-induced GIM and human specimens. GATA4 bound to the promoter of mucin 2 (MUC2) and stimulate its transcription. GATA4 and MUC2 expression was positively correlated in GIM tissues. Nuclear transcription factor-κB activation was required for the upregulation of GATA4 and MUC2 in bile acid-induced GIM cell models. GATA4 and caudal-related homeobox 2 (CDX2) reciprocally transactivated each other to drive the transcription of MUC2. In chenodeoxycholic acid-treated mice, MUC2, CDX2, GATA4, p50, and p65 expression levels were increased in the gastric mucosa.

Conclusions

GATA4 is upregulated and can form a positive feedback loop with CDX2 to transactivate MUC2 in GIM. NF-κB signaling is involved in the upregulation of GATA4 by chenodeoxycholic acid.

Cingulin family: Structure, function and clinical significance

Cingulin and its paralog paracingulin are vital components of the apical junctional complex in vertebrate epithelial and endothelial cells. They are both found in tight junctions (TJ), and paracingulin is also detectable in adherens junctions (AJ) as TJ cytoplasmic plaque proteins. Cingulin and paracingulin interact with other proteins to perform functions. They interact with cytoskeletal proteins, modulate the activity of small GTPases, such as RhoA and Rac1, and regulate gene expression. In addition, cingulin and paracingulin regulate barrier function and many pathological processes, including inflammation and tumorigenesis. In this review, we summarize the discovery and structure, expression and subcellular distribution, and molecular interactions of cingulin family proteins and discuss their role in development, physiology, and pathological processes.

The dopamine transporter antagonist vanoxerine inhibits G9a and suppresses cancer stem cell functions in colon tumors

Cancer stem cells (CSCs), functionally characterized by self-renewal and tumor-initiating activity, contribute to decreased tumor immunogenicity, while fostering tumor growth and metastasis. Targeting G9a histone methyltransferase (HMTase) effectively blocks CSC functions in colorectal tumors by altering pluripotent-like molecular networks; however, existing molecules directly targeting G9a HMTase activity failed to reach clinical stages due to safety concerns. Using a stem cell-based phenotypic drug-screening pipeline, we identified the dopamine transporter (DAT) antagonist vanoxerine, a compound with previously demonstrated clinical safety, as a cancer-specific downregulator of G9a expression. Here we show that gene silencing and chemical antagonism of DAT impede colorectal CSC functions by repressing G9a expression. Antagonizing DAT also enhanced tumor lymphocytic infiltration by activating endogenous transposable elements and type-I interferon response. Our study unveils the direct implication of the DAT-G9a axis in the maintenance of CSC populations and an approach to improve antitumor immune response in colon tumors.

Gastric Intestinal Metaplasia: Real Culprit or Innocent Bystander as a Precancerous Condition for Gastric Cancer?

Gastric intestinal metaplasia (GIM), which denotes conversion of gastric mucosa into an intestinal phenotype, can occur in all regions of the stomach, including cardiac, fundic, and pyloric mucosa. Since the earliest description of GIM, its association with gastric cancer of the differentiated (intestinal) type has been a well-recognized concern. Many epidemiologic studies have confirmed GIM to be significantly associated with subsequent gastric cancer development. Helicobacter pylori, the principal etiologic factor for gastric cancer, plays the most important role in predisposing to GIM. Although the role of GIM in the stepwise progression model of gastric carcinogenesis (the so-called "Correa cascade") has come into question recently, we review the scientific evidence that strongly supports this long-standing model and propose a new progression model that builds on the Correa cascade. Eradication of H pylori is the most important method for preventing gastric cancer globally, but the effect of eradication on established GIM, is limited, if any. Endoscopic surveillance for GIM may, therefore, be necessary, especially when there is extensive corpus GIM. Recent advances in image-enhanced endoscopy with integrated artificial intelligence have facilitated the identification of GIM and neoplastic lesions, which will impact preventive strategies in the near future.

Integrin α7β1 represses intestinal absorptive cell differentiation

Intestinal epithelial cell differentiation is a highly controlled and orderly process occurring in the crypt so that cells migrating out to cover the villi are already fully functional. Absorptive cell precursors, which originate from the stem cell population located in the lower third of the crypt, are subject to several cycles of amplification in the transit amplifying (TA) zone, before reaching the terminal differentiation compartment located in the upper third. There is a large body of evidence that absorptive cell differentiation is halted in the TA zone through various epigenetic, transcriptional and intracellular signalling events or mechanisms allowing the transient expansion of this cell population but how these mechanisms are themself regulated remains obscure. One clue can be found in the epithelial cell-matrix microenvironment located all along the crypt-villus axis. Indeed, a previous study from our group revealed that α5-subunit containing laminins such as lamimin-511 and 512 inhibit early stages of differentiation in Caco-2/15 cells. Among potential receptors for laminin 511/512 is the integrin α7β1, which has previously been reported to be expressed in the human intestinal crypts and in early stages of Caco-2/15 cell differentiation. In this study, the effects of knocking down ITGA7 in Caco-2/15 cells were studied using shRNA and CRISPR/Cas9 strategies. Abolition of the α7 integrin subunit resulted in a significant increase in the level of differentiation and polarization markers as well as the morphological features of intestinal cells. Activities of focal adhesion kinase and Src kinase were both reduced in α7-knockdown cells while the three major intestinal pro-differentiation factors CDX2, HNFα1 and HNF4α were overexpressed. Two epigenetic events associated with intestinal differentiation, the reduction of tri-methylated lysine 27 on histone H3 and the increase of acetylation of histone H4 were also observed in α7-knockdown cells. On the other hand, the ablation of α7 had no effect on cell proliferation. In conclusion, these data indicate that integrin α7β1 acts as a major repressor of absorptive cell terminal differentiation in the Caco-2/15 cell model and suggest that the laminin-α7β1 integrin interaction occurring in the transit amplifying zone of the adult intestine is involved in the transient halting of absorptive cell terminal differentiation.

The Combination of Gold and Silver Food Nanoparticles with Gluten Peptides Alters the Autophagic Pathway in Intestinal Crypt-like Cells

Metallic nanoparticles (mNPs) are widely used as food additives and can interact with gliadin triggering an immune response, but evaluation of the effects on crypts, hypertrophic in celiac subjects, is still lacking. This study evaluated the effects of gold and silver mNPs in combination with gliadin on crypt-like cells (HIEC-6). Transmission electron microscopy (TEM) was used to evaluate gliadin-mNP aggregates in cells. Western blot and immunofluorescence analysis assessed autophagy-related molecule levels (p62, LC3, beclin-1, EGFR). Lysosome functionality was tested with acridine orange (AO) and Magic Red assays. TEM identified an increase in autophagic vacuoles after exposure to gliadin + mNPs, as also detected by significant increments in LC3-II and p62 expression. Immunofluorescence confirmed the presence of mature autophagosomes, showing LC3 and p62 colocalization, indicating an altered autophagic flux, further assessed with EGFR degradation, AO and Magic Red assays. The results showed a significant reduction in lysosomal enzyme activity and a modest reduction in acidity. Thus, gliadin + mNPs can block the autophagic flux inducing a lysosomal defect. The alteration of this pathway, essential for cell function, can lead to cell damage and death. The potential effects of this copresence in food should be further characterized to avoid a negative impact on celiac disease subjects.

Primary Cilium Identifies a Quiescent Cell Population in the Human Intestinal Crypt

Primary cilia are sensory antennae located at the cell surface which mediate a variety of extracellular signals involved in development, tissue homeostasis, stem cells and cancer. Primary cilia are found in an extensive array of vertebrae cells but can only be generated when cells become quiescent. The small intestinal epithelium is a rapidly self-renewing tissue organized into a functional unit called the crypt–villus axis, containing progenitor and differentiated cells, respectively. Terminally differentiated villus cells are notoriously devoid of primary cilia. We sought to determine if intestinal crypts contain a quiescent cell population that could be identified by the presence of primary cilia. Here we show that primary cilia are detected in a subset of cells located deep in the crypts slightly above a Paneth cell population. Using a normal epithelial proliferative crypt cell model, we show that primary cilia assembly and activity correlate with a quiescent state. These results provide further evidence for the existence of a quiescent cell population in the human small intestine and suggest the potential for new modes of regulation in stem cell dynamics.

A Kaleidoscope of Keratin Gene Expression and the Mosaic of Its Regulatory Mechanisms

Keratins are a family of intermediate filament-forming proteins highly specific to epithelial cells. A combination of expressed keratin genes is a defining property of the epithelium belonging to a certain type, organ/tissue, cell differentiation potential, and at normal or pathological conditions. In a variety of processes such as differentiation and maturation, as well as during acute or chronic injury and malignant transformation, keratin expression undergoes switching: an initial keratin profile changes accordingly to changed cell functions and location within a tissue as well as other parameters of cellular phenotype and physiology. Tight control of keratin expression implies the presence of complex regulatory landscapes within the keratin gene loci. Here, we highlight patterns of keratin expression in different biological conditions and summarize disparate data on mechanisms controlling keratin expression at the level of genomic regulatory elements, transcription factors (TFs), and chromatin spatial structure.

Weaning stress and intestinal health of piglets: A review

Weaning is considered to be one of the most critical periods in pig production, which is related to the economic benefits of pig farms. However, in actual production, many piglets are often subjected to weaning stress due to the sudden separation from the sow, the changes in diet and living environment, and other social challenges. Weaning stress often causes changes in the morphology and function of the small intestine of piglets, disrupts digestion and absorption capacity, destroys intestinal barrier function, and ultimately leads to reduced feed intake, increased diarrhea rate, and growth retardation. Therefore, correctly understanding the effects of weaning stress on intestinal health have important guiding significance for nutritional regulation of intestinal injury caused by weaning stress. In this review, we mainly reviewed the effects of weaning stress on the intestinal health of piglets, from the aspects of intestinal development, and intestinal barrier function, thereby providing a theoretical basis for nutritional strategies to alleviate weaning stress in mammals in future studies.

Differential influence of YAP1 and TAZ on differentiation of intestinal epithelial cell: A review

Intestinal cell stemness, proliferation and differentiation are complex processes all occurring in distinct compartments of the crypt that need to be closely regulated to ensure proper epithelial renewal. The involvement of the Hippo pathway in intestinal epithelial proliferation and regeneration after injury via the regulation of its effectors YAP1 and TAZ has been well-documented over the last decade. The implication of YAP1 and TAZ on intestinal epithelial cell differentiation is less clear. Using intestinal cell models in which the expression of YAP1 and TAZ can be modulated, our group showed that YAP1 inhibits differentiation of the two main intestinal epithelial cell types, goblet and absorptive cells through a specific mechanism involving the repression of prodifferentiation transcription factor CDX2 expression. Further analysis provided evidence that the repressive effect of YAP1 on intestinal differentiation is mediated by regulation of the Hippo pathway by Src family kinase activity. Interestingly, the TAZ paralog does not seem to be involved in this process, which provides another example of the lack of perfect complementarity of the two main Hippo effectors.

Epithelial de-differentiation triggered by co-ordinate epigenetic inactivation of the EHF and CDX1 transcription factors drives colorectal cancer progression

Colorectal cancers (CRCs) often display histological features indicative of aberrant differentiation but the molecular underpinnings of this trait and whether it directly drives disease progression is unclear. Here, we identify co-ordinate epigenetic inactivation of two epithelial-specific transcription factors, EHF and CDX1, as a mechanism driving differentiation loss in CRCs. Re-expression of EHF and CDX1 in poorly-differentiated CRC cells induced extensive chromatin remodelling, transcriptional re-programming, and differentiation along the enterocytic lineage, leading to reduced growth and metastasis. Strikingly, EHF and CDX1 were also able to reprogramme non-colonic epithelial cells to express colonic differentiation markers. By contrast, inactivation of EHF and CDX1 in well-differentiated CRC cells triggered tumour de-differentiation. Mechanistically, we demonstrate that EHF physically interacts with CDX1 via its PNT domain, and that these transcription factors co-operatively drive transcription of the colonic differentiation marker, VIL1. Compound genetic deletion of Ehf and Cdx1 in the mouse colon disrupted normal colonic differentiation and significantly enhanced colorectal tumour progression. These findings thus reveal a novel mechanism driving epithelial de-differentiation and tumour progression in CRC.

Simian Immunodeficiency Virus Infection Mediated Changes in Jejunum and Peripheral SARS-CoV-2 Receptor ACE2 and Associated Proteins or Genes in Rhesus Macaques

Angiotensin converting enzyme-2 (ACE2) and associated proteins play a pivotal role in various physiological and pathological events, such as immune activation, inflammation, gut barrier maintenance, intestinal stem cell proliferation, and apoptosis. Although many of these clinical events are quite significant in SIV/HIV infection, expression profiling of these proteins has not been well reported. Considering the different pathological consequences in the gut after HIV infection, we hypothesized that the expression of ACE2 and associated proteins of the Renin-angiotensin system (RAS) could be compromised after SIV/HIV infection. We quantified the gene expression of ACE2 as well as AGTR1/2, ADAM17, and TMPRSS2, and compared between SIV infected and uninfected rhesus macaques (Macaca mulatta; hereafter abbreviated RMs). The gene expression analysis revealed significant downregulation of ACE2 and upregulation of AGTR2 and inflammatory cytokine IL-6 in the gut of infected RMs. Protein expression profiling also revealed significant upregulation of AGTR2 after infection. The expression of ACE2 in protein level was also decreased, but not significantly, after infection. To understand the entirety of the process in newly regenerated epithelial cells, a global transcriptomic study of enteroids raised from intestinal stem cells was performed. Interestingly, most of the genes associated with the RAS, such as DPP4, MME, ANPEP, ACE2, ENPEP, were found to be downregulated in SIV infection. HNFA1 was found to be a key regulator of ACE2 and related protein expression. Jejunum CD4+ T cell depletion and increased IL-6 mRNA, MCP-1 and AGTR2 expression may signal inflammation, monocyte/macrophage accumulation and epithelial apoptosis in accelerating SIV pathogenesis. Overall, the findings in the study suggested a possible impact of SIV/HIV infection on expression of ACE2 and RAS-associated proteins resulting in the loss of gut homeostasis. In the context of the current COVID-19 pandemic, the outcome of SARS-CoV-2 and HIV co-infection remains uncertain and needs further investigation as the significance profile of ACE2, a viral entry receptor for SARS-CoV-2, and its expression in mRNA and protein varied in the current study. There is a concern of aggravated SARS-CoV-2 outcomes due to possible serious pathological events in the gut resulting from compromised expression of RAS- associated proteins in SIV/HIV infection.

Pharmacological targeting of Sam68 functions in colorectal cancer stem cells

Cancer stem cells (CSCs) are documented to play a key role in tumorigenesis and therapy resistance. Despite significant progress in clinical oncology, CSC reservoirs remain elusive and difficult to eliminate. Reverse-turn peptidomimetics were characterized as disruptors of CBP/beta-Catenin interactions and represent a promising avenue to curb hyperactive canonical Wnt/beta-Catenin signaling in CSCs. Recent studies suggested Sam68 as a critical mediator of reverse-turn peptidomimetics response in CSC populations. Using computational and biochemical approaches we confirmed Sam68 as a primary target of reverse-turn peptidomimetics. Furthermore, we executed an in silico drug discovery pipeline to identify yet uncharacterized reverse-turn peptidomimetic structures displaying superior anti-CSC activity in transformed pluripotent and colorectal cancer cell models. Thus, we identified YB-0158 as a reverse-turn peptidomimetic small molecule with enhanced translational potential, altering key hallmarks of human colorectal CSCs in patient-derived ex vivo organoids and in vivo serial tumor transplantation.

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Sam68 is a direct protein target of reverse-turn peptidomimetic small molecules

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YB-0158 is a peptidomimetic structure with high predicted affinity for Sam68

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YB-0158 elicits a cancer-selective response impeding main cancer stem cell hallmarks

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YB-0158 blocks cancer stem cell activity in tumor organoids and in vivo systems

P63 Deficiency and CDX2 Overexpression Lead to Barrett's-Like Metaplasia in Mouse Esophageal Epithelium

BACKGROUND

The cellular origin and molecular mechanisms of Barrett's esophagus (BE) are still controversial. Trans-differentiation is a mechanism characterized by activation of the intestinal differentiation program and inactivation of the squamous differentiation program.

AIMS

Renal capsule grafting (RCG) was used to elucidate whether CDX2 overexpression on the basis of P63 deficiency in the esophageal epithelium may generate intestinal metaplasia.

METHODS

P63^-/-;Villin-Cdx2 embryos were generated by crossing P63^+/- mice with Villin-Cdx2 mice. E18.5 esophagus was xenografted in a renal capsule grafting (RCG) model. At 1, 2, or 4 weeks after RCG, the mouse esophagus was immunostained for a proliferation marker (BrdU), squamous transcription factors (SOX2, PAX9), squamous differentiation markers (CK5, CK4, and CK1), intestinal transcription factors (CDX1, HNF1α, HNF4α, GATA4, and GATA6), intestinal columnar epithelial cell markers (A33, CK8), goblet cell marker (MUC2, TFF3), Paneth cell markers (LYZ and SOX9), enteroendocrine cell marker (CHA), and Tuft cell marker (DCAMKL1).

RESULTS

The P63^-/-;Villin-Cdx2 RCG esophagus was lined with proliferating PAS/AB+ cuboidal cells and formed an intestinal crypt-like structure. The goblet cell markers (TFF3 and MUC2) and intestinal transcription factors (CDX1, HNF1α, HNF4α, GATA4, and GATA6) were expressed although no typical morphology of goblet cells was observed. Other intestinal cell markers including enteroendocrine cell marker (CHA), Paneth cell markers (LYZ and Sox9), and intestinal secretory cell marker (UEA/WGA) were also expressed in the P63^-/-;Villin-Cdx2 RCG esophagus. Squamous cell markers (PAX9 and SOX2) were also expressed, suggesting a transitional phenotype.

CONCLUSION

CDX2 overexpression on the basis of P63 deficiency in esophageal epithelial cells induces Barrett's-like metaplasia in vivo. Additional factors may be needed to drive this transitional phenotype into full-blown BE.

Src family kinases inhibit differentiation of intestinal epithelial cells through the Hippo effector YAP1

Intestinal cell lineage differentiation is a tightly regulated mechanism that involves several intracellular signaling pathways affecting the expression of a variety of transcription factors, which ultimately regulate cell specific gene expression. Absorptive and goblet cells are the two main epithelial cell types of the intestine. Previous studies from our group using an shRNA knockdown approach have shown that YAP1, one of the main Hippo pathway effectors, inhibits the differentiation of these two cell types. In the present study, we show that YAP1 activity is regulated by Src family kinases (SFKs) in these cells. Inhibition of SFKs led to a sharp reduction in YAP1 expression at the protein level, an increase in CDX2 and the P1 forms of HNF4α and of absorptive and goblet cell differentiation specific markers. Interestingly, in Caco-2/15 cells which express both YAP1 and its paralog TAZ, TAZ was not reduced by the inhibition of SFKs and its specific knockdown rather impaired absorptive cell differentiation indicating that YAP1 and TAZ are not always interchangeable for regulating cell functions.

This article has an associated First Person interview with the first author of the paper.

Summary: Inhibition of Src family kinases leads to a sharp reduction in YAP1 expression and an increase in CDX2 and HNF4α, two regulators of intestinal cell differentiation, while its paralog TAZ appears not to be directly involved.

Loss of mismatch repair signaling impairs the WNT-bone morphogenetic protein crosstalk and the colonic homeostasis

The fine balance between proliferation, differentiation, and apoptosis in the colonic epithelium is tightly controlled by the interplay between WNT, Notch, and bone morphogenetic protein (BMP) signaling. How these complex networks coordinate the colonic homeostasis, especially if cancer predisposing mutations such as mutations in the DNA mismatch repair (MMR) are present, is unclear. Inactivation of the MMR system has long been linked to colorectal cancer; however, little is known about its role in the regulation of the colonic homeostasis. It has been shown that loss of MMR promotes the proliferation of colon epithelial cells that renders them highly susceptible to transformation. The mechanism through which MMR mediates this effect, yet, remains to be determined. Using an MMR-deficient mouse model, we show that increased methylation of Dickkopf1 impacts its expression, and consequently, the ability to negatively regulate WNT signaling. As a result, excessive levels of active β-catenin promote strong crypt progenitor-like phenotype and abnormal proliferation. Under these settings, the development and function of the goblet cells are affected. MMR-deficient mice have fewer goblet cells with enlarged mucin-loaded vesicles. We further show that MMR inactivation impacts the WNT–BMP signaling crosstalk.

miR-802 regulates Paneth cell function and enterocyte differentiation in the mouse small intestine

The intestinal epithelium is a complex structure that integrates digestive, immunological, neuroendocrine, and regenerative functions. Epithelial homeostasis is maintained by a coordinated cross-talk of different epithelial cell types. Loss of integrity of the intestinal epithelium plays a key role in inflammatory diseases and gastrointestinal infection. Here we show that the intestine-enriched miR-802 is a central regulator of intestinal epithelial cell proliferation, Paneth cell function, and enterocyte differentiation. Genetic ablation of mir-802 in the small intestine of mice leads to decreased glucose uptake, impaired enterocyte differentiation, increased Paneth cell function and intestinal epithelial proliferation. These effects are mediated in part through derepression of the miR-802 target Tmed9, a modulator of Wnt and lysozyme/defensin secretion in Paneth cells, and the downstream Wnt signaling components Fzd5 and Tcf4. Mutant Tmed9 mice harboring mutations in miR-802 binding sites partially recapitulate the augmented Paneth cell function of mice lacking miR-802. Our study demonstrates a broad miR-802 network that is important for the integration of signaling pathways of different cell types controlling epithelial homeostasis in the small intestine.

Targeting SUMOylation dependency in human cancer stem cells through a unique SAE2 motif revealed by chemical genomics

Natural products (NPs) encompass a rich source of bioactive chemical entities. Here, we used human cancer stem cells (CSCs) in a chemical genomics campaign with NP chemical space to interrogate extracts from diverse strains of actinomycete for anti-cancer properties. We identified a compound (McM25044) capable of selectively inhibiting human CSC function versus normal stem cell counterparts. Biochemical and molecular studies revealed that McM025044 exerts inhibition on human CSCs through the small ubiquitin-like modifier (SUMO) cascade, found to be hyperactive in a variety of human cancers. McM025044 impedes the SUMOylation pathway via direct targeting of the SAE1/2 complex. Treatment of patient-derived CSCs resulted in reduced levels of SUMOylated proteins and suppression of progenitor and stem cell capacity measured in vitro and in vivo. Our study overcomes a barrier in chemically inhibiting oncogenic SUMOylation activity and uncovers a unique role for SAE2 in the biology of human cancers.

Chromatin Dynamics in Intestinal Epithelial Homeostasis: A Paradigm of Cell Fate Determination versus Cell Plasticity

The rapid renewal of intestinal epithelium is mediated by a pool of stem cells, located at the bottom of crypts, giving rise to highly proliferative progenitor cells, which in turn differentiate during their migration along the villus. The equilibrium between renewal and differentiation is critical for establishment and maintenance of tissue homeostasis, and is regulated by signaling pathways (Wnt, Notch, Bmp…) and specific transcription factors (TCF4, CDX2…). Such regulation controls intestinal cell identities by modulating the cellular transcriptome. Recently, chromatin modification and dynamics have been identified as major actors linking signaling pathways and transcriptional regulation in the control of intestinal homeostasis. In this review, we synthesize the many facets of chromatin dynamics involved in controlling intestinal cell fate, such as stemness maintenance, progenitor identity, lineage choice and commitment, and terminal differentiation. In addition, we present recent data underlying the fundamental role of chromatin dynamics in intestinal cell plasticity. Indeed, this plasticity, which includes dedifferentiation processes or the response to environmental cues (like microbiota’s presence or food ingestion), is central for the organ’s physiology. Finally, we discuss the role of chromatin dynamics in the appearance and treatment of diseases caused by deficiencies in the aforementioned mechanisms, such as gastrointestinal cancer, inflammatory bowel disease or irritable bowel syndrome.

The Hippo Pathway Effector YAP1 Regulates Intestinal Epithelial Cell Differentiation

The human intestine is covered by epithelium, which is continuously replaced by new cells provided by stem cells located at the bottom of the glands. The maintenance of intestinal stem cells is supported by a niche which is composed of several signaling proteins including the Hippo pathway effectors YAP1/TAZ. The role of YAP1/TAZ in cell proliferation and regeneration is well documented but their involvement on the differentiation of intestinal epithelial cells is unclear. In the present study, the role of YAP1/TAZ on the differentiation of intestinal epithelial cells was investigated using the HT29 cell line, the only multipotent intestinal cell line available, with a combination of knockdown approaches. The expression of intestinal differentiation cell markers was tested by qPCR, Western blot, indirect immunofluorescence and electron microscopy analyses. The results show that TAZ is not expressed while the abolition of YAP1 expression led to a sharp increase in goblet and absorptive cell differentiation and reduction of some stem cell markers. Further studies using double knockdown experiments revealed that most of these effects resulting from YAP1 abolition are mediated by CDX2, a key intestinal cell transcription factor. In conclusion, our results indicate that YAP1/TAZ negatively regulate the differentiation of intestinal epithelial cells through the inhibition of CDX2 expression.

The H2A.Z histone variant integrates Wnt signaling in intestinal epithelial homeostasis

The Tip60/p400 chromatin-modifying complex, which is involved in the incorporation and post-translational modification of the H2A.Z histone variant, regulates cell proliferation and important signaling pathways, such as Wnt. Here, we study the involvement of H2A.Z in intestinal epithelial homeostasis, which is dependent on the finely-tuned equilibrium between stem cells renewal and differentiation, under the control of such pathway. We use cell models and inducible knock-out mice to study the impact of H2A.Z depletion on intestinal homeostasis. We show that H2A.Z is essential for the proliferation of human cancer and normal intestinal crypt cells and negatively controls the expression of a subset of differentiation markers, in cultured cells and mice. H2A.Z impairs the recruitment of the intestine-specific transcription factor CDX2 to chromatin, is itself a target of the Wnt pathway and thus, acts as an integrator for Wnt signaling in the control of intestinal epithelial cell fate and homeostasis.

The histone variant, H2A.Z is known to regulate gene expression and cell proliferation. Here the authors show that H2A.Z has a central role in the control of intestinal epithelial homeostasis in mice, by preventing terminal differentiation of intestinal progenitors.

Tight junction proteins in gastrointestinal and liver disease

Over the past two decades a growing body of evidence has demonstrated an important role of tight junction (TJ) proteins in the physiology and disease biology of GI and liver disease. On one side, TJ proteins exert their functional role as integral proteins of TJs in forming barriers in the gut and the liver. Furthermore, TJ proteins can also be expressed outside TJs where they play important functional roles in signalling, trafficking and regulation of gene expression. A hallmark of TJ proteins in disease biology is their functional role in epithelial-to-mesenchymal transition. A causative role of TJ proteins has been established in the pathogenesis of colorectal cancer and gastric cancer. Among the best characterised roles of TJ proteins in liver disease biology is their function as cell entry receptors for HCV-one of the most common causes of hepatocellular carcinoma. At the same time TJ proteins are emerging as targets for novel therapeutic approaches for GI and liver disease. Here we review our current knowledge of the role of TJ proteins in the pathogenesis of GI and liver disease biology and discuss their potential as therapeutic targets.

Identification of Novel Molecules Targeting Cancer Stem Cells

Multiple studies focused on tumor heterogeneity and cellular hierarchies have demonstrated the role of cancer stem cells (CSC) in tumor initiation and recurrence. Colorectal cancer is one of the leading causes of cancer-related death and is hierarchically organized, with the majority of tumor cells descending from a small population of colon cancer stem cells (CCSCs). Such a rare self-renewing population is marked by the acquisition of distinct chromatin regulation and transcriptional programs. Fundamental molecular deviations between CCSCs and bulk tumor cells as well as normal tissues represent a unique therapeutic access to develop novel, selective anticancer therapies.In this chapter, we describe a methodological pipeline to identify novel molecules to selectively target human CCSC. We present a point-by-point description of a typical phenotypic molecular screening experiment, aiming to identify selective modulators of human CCSCs vs. normal intestinal progenitor cells.

Knockdown of laminin α5 stimulates intestinal cell differentiation

Interactions between cells and the extracellular matrix regulate a wide range of cell processes such as proliferation and differentiation. Laminins are major components of the basement membrane that actively participate in most biological functions via their interactions with a variety of specific cell receptors. The α5-containing laminins (LAMA5) are one of the three main types of laminins identified at the epithelial basal lamina in the adult intestine. The aim of the present study was to investigate the role of α5-containing laminins on intestinal cell proliferation and differentiation. Using an shRNA targeting approach, the effects of knocking down the expression of LAMA5 were investigated in the enterocytic-like Caco-2/15 cell line, a well-characterized model for intestinal cell differentiation. Surprisingly, the abolition of the laminin α5 chain resulted in a drastic increase in the differentiation marker sucrase-isomaltase which was correctly expressed at the apical pole of the cells as observed by indirect immunofluorescence. Transient increases of dipeptidylpeptidase IV, villin, CDX2, HNF-1α, HNF-4α and transepithelial resistance as well as an apparent redistribution of the junctional components ZO-1 and E-cadherin were also observed at early stages of differentiation but no specific effect was observed on cell proliferation as evaluated by BrdU incorporation. Taken together, these data suggest that α5-containing laminins repress intestinal differentiation in its early stages.

CDX2 Stimulates the Proliferation of Porcine Intestinal Epithelial Cells by Activating the mTORC1 and Wnt/β-Catenin Signaling Pathways

Caudal type homeobox 2 (CDX2) is expressed in intestinal epithelial cells and plays a role in gut development and homeostasis by regulating cell proliferation. However, whether CDX2 cooperates with the mammalian target of rapamycin complex 1 (mTORC1) and Wnt/β-catenin signaling pathways to stimulate cell proliferation remains unknown. The objective of this study was to investigate the effect of CDX2 on the proliferation of porcine jejunum epithelial cells (IPEC-J2) and the correlation between CDX2, the mTORC1 and Wnt/β-catenin signaling pathways. CDX2 overexpression and knockdown cell culture models were established to explore the regulation of CDX2 on both pathways. Pathway-specific antagonists were used to verify the effects. The results showed that CDX2 overexpression increased IPEC-J2 cell proliferation and activated both the mTORC1 and Wnt/β-catenin pathways, and that CDX2 knockdown decreased cell proliferation and inhibited both pathways. Furthermore, the mTORC1 and Wnt/β-catenin pathway-specific antagonist rapamycin and XAV939 (3,5,7,8-tetrahydro-2-[4-(trifluoromethyl)]-4H -thiopyrano[4,3-d]pyrimidin-4-one) both suppressed the proliferation of IPEC-J2 cells overexpressing CDX2, and that the combination of rapamycin and XAV939 had an additive effect. Regardless of whether the cells were treated with rapamycin or XAV939 alone or in combination, both mTORC1 and Wnt/β-catenin pathways were down-regulated, accompanied by a decrease in CDX2 expression. Taken together, our data indicate that CDX2 stimulates porcine intestinal epithelial cell proliferation by activating the mTORC1 and Wnt/β-catenin signaling pathways.

Acute myeloid leukaemia disrupts endogenous myelo-erythropoiesis by compromising the adipocyte bone marrow niche

Acute myeloid leukaemia (AML) is distinguished by the generation of dysfunctional leukaemic blasts, and patients characteristically suffer from fatal infections and anaemia due to insufficient normal myelo-erythropoiesis. Direct physical crowding of bone marrow (BM) by accumulating leukaemic cells does not fully account for this haematopoietic failure. Here, analyses from AML patients were applied to both in vitro co-culture platforms and in vivo xenograft modelling, revealing that human AML disease specifically disrupts the adipocytic niche in BM. Leukaemic suppression of BM adipocytes led to imbalanced regulation of endogenous haematopoietic stem and progenitor cells, resulting in impaired myelo-erythroid maturation. In vivo administration of PPARγ agonists induced BM adipogenesis, which rescued healthy haematopoietic maturation while repressing leukaemic growth. Our study identifies a previously unappreciated axis between BM adipogenesis and normal myelo-erythroid maturation that is therapeutically accessible to improve symptoms of BM failure in AML via non-cell autonomous targeting of the niche.

Histone deacetylase inhibition impairs normal intestinal cell proliferation and promotes specific gene expression

Mechanisms that maintain proliferation and delay cell differentiation in the intestinal crypt are not yet fully understood. We have previously shown the implication of histone methylation in the regulation of enterocytic differentiation. In this study, we investigated the role of histone deacetylation as an important epigenetic mechanism that controls proliferation and differentiation of intestinal cells using the histone deacetylase inhibitor suberanilohydroxamic acid (SAHA) on the proliferation and differentiation of human and mouse intestinal cells. Treatment of newly confluent Caco‐2/15 cells with SAHA resulted in growth arrest, increased histone acetylation and up‐regulation of the expression of intestine‐specific genes such as those encoding sucrase‐isomaltase, villin and the ion exchanger SLC26A3. Although SAHA has been recently used in clinical trials for cancer treatment, its effect on normal intestinal cells has not been documented. Analyses of small and large intestines of mice treated with SAHA revealed a repression of crypt cell proliferation and a higher expression of sucrase‐isomaltase in both segments compared to control mice. Expression of SLC26A3 was also significantly up‐regulated in the colons of mice after SAHA administration. Finally, SAHA was also found to strongly inhibit normal human intestinal crypt cell proliferation in vitro. These results demonstrate the important implication of epigenetic mechanisms such as histone acetylation/deacetylation in the regulation of normal intestinal cell fate and proliferation. J. Cell. Biochem. 116: 2695–2708, 2015. © 2015 The Authors. Journal of Cellular Biochemistry published by Wiley Periodicals, Inc.

Epigenetics in Intestinal Epithelial Cell Renewal

A controlled balance between cell proliferation and differentiation is essential to maintain normal intestinal tissue renewal and physiology. Such regulation is powered by several intracellular pathways that are translated into the establishment of specific transcription programs, which influence intestinal cell fate along the crypt-villus axis. One important check-point in this process occurs in the transit amplifying zone of the intestinal crypts where different signaling pathways and transcription factors cooperate to manage cellular proliferation and differentiation, before secretory or absorptive cell lineage terminal differentiation. However, the importance of epigenetic modifications such as histone methylation and acetylation in the regulation of these processes is still incompletely understood. There have been recent advances in identifying the impact of histone modifications and chromatin remodelers on the proliferation and differentiation of normal intestinal crypt cells. In this review we discuss recent discoveries on the role of the cellular epigenome in intestinal cell fate, development, and tissue renewal. J. Cell. Physiol. 231: 2361-2367, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

Hepatocyte nuclear factor 1 coordinates multiple processes in a model of intestinal epithelial cell function

Mutations in hepatocyte nuclear factor 1 transcription factors (HNF1α/β) are associated with diabetes. These factors are well studied in the liver, pancreas and kidney, where they direct tissue-specific gene regulation. However, they also have an important role in the biology of many other tissues, including the intestine. We investigated the transcriptional network governed by HNF1 in an intestinal epithelial cell line (Caco2). We used chromatin immunoprecipitation followed by direct sequencing (ChIP-seq) to identify HNF1 binding sites genome-wide. Direct targets of HNF1 were validated using conventional ChIP assays and confirmed by siRNA-mediated depletion of HNF1, followed by RT-qPCR. Gene ontology process enrichment analysis of the HNF1 targets identified multiple processes with a role in intestinal epithelial cell function, including properties of the cell membrane, cellular response to hormones, and regulation of biosynthetic processes. Approximately 50% of HNF1 binding sites were also occupied by other members of the intestinal transcriptional network, including hepatocyte nuclear factor 4A (HNF4A), caudal type homeobox 2 (CDX2), and forkhead box A2 (FOXA2). Depletion of HNF1 in Caco2 cells increases FOXA2 abundance and decreases levels of CDX2, illustrating the coordinated activities of the network. These data suggest that HNF1 plays an important role in regulating intestinal epithelial cell function, both directly and through interactions with other intestinal transcription factors.

DNA Methylation Dynamics During Differentiation, Proliferation, and Tumorigenesis in the Intestinal Tract

DNA methylation, an epigenetic control mechanism in mammals, is widely present in the intestinal tract during the differentiation and proliferation of epithelial cells. Cells in stem cell pools or villi have different patterns of DNA methylation. The process of DNA methylation is dynamic and occurs at many relevant regulatory elements during the rapid transition of stem cells into fully mature, differentiated epithelial cells. Changes in DNA methylation patterns most often take place in enhancer and promoter regions and are associated with transcription factor binding. During differentiation, enhancer regions associated with genes important to enterocyte differentiation are demethylated, activating gene expression. Abnormal patterns of DNA methylation during differentiation and proliferation in the intestinal tract can lead to the formation of aberrant crypt foci and destroy the barrier and absorptive functions of the intestinal epithelium. Accumulation of these epigenetic changes may even result in tumorigenesis. In the current review, we discuss recent findings on the association between DNA methylation and cell differentiation and proliferation in the small intestine and highlight the possible links between dysregulation of this process and tumorigenesis.

Glucose Tolerance Is Improved in Mice Invalidated for the Nuclear Receptor HNF-4γ: A Critical Role for Enteroendocrine Cell Lineage

Intestine contributes to energy homeostasis through the absorption, metabolism, and transfer of nutrients to the organism. We demonstrated previously that hepatocyte nuclear receptor-4α (HNF-4α) controls intestinal epithelium homeostasis and intestinal absorption of dietary lipids. HNF-4γ, the other HNF-4 form highly expressed in intestine, is much less studied. In HNF-4γ knockout mice, we detect an exaggerated insulin peak and improvement in glucose tolerance during oral but not intraperitoneal glucose tolerance tests, highlighting the involvement of intestine. Moreover, the enteroendocrine L-type cell lineage is modified, as assessed by the increased expression of transcription factors Isl1, Foxa1/2, and Hnf4a, leading to an increase of both GLP-1-positive cell number and basal and stimulated GLP-1 plasma levels potentiating the glucose-stimulated insulin secretion. Using the GLP-1 antagonist exendin (9-39), we demonstrate a direct effect of GLP-1 on improved glucose tolerance. GLP-1 exerts a trophic effect on pancreatic β-cells, and we report an increase of the β-cell fraction correlated with an augmented number of proliferative islet cells and with resistance to streptozotocin-induced diabetes. In conclusion, the loss of HNF-4γ improves glucose homeostasis through a modulation of the enteroendocrine cell lineage.

Cryosectioning the intestinal crypt-villus axis: an ex vivo method to study the dynamics of epigenetic modifications from stem cells to differentiated cells

The intestinal epithelium is a particularly attractive biological adult model to study epigenetic mechanisms driving adult stem cell renewal and cell differentiation. Since epigenetic modifications are dynamic, we have developed an original ex vivo approach to study the expression and epigenetic profiles of key genes associated with either intestinal cell pluripotency or differentiation by isolating cryosections of the intestinal crypt-villus axis. Gene expression, DNA methylation and histone modifications were studied by qRT-PCR, methylation-specific PCR and micro-chromatin immunoprecipitation, respectively. Using this approach, it was possible to identify segment-specific methylation and chromatin profiles. We show that (i) expression of intestinal stem cell markers (Lgr5, Ascl2) exclusively in the crypt is associated with active histone marks, (ii) promoters of all pluripotency genes studied and transcription factors involved in intestinal cell fate (Cdx2) harbour a bivalent chromatin pattern in the crypts and (iii) expression of differentiation markers (Muc2, Sox9) along the crypt-villus axis is associated with DNA methylation. Hence, using an original model of cryosectioning along the crypt-villus axis that allows in situ detection of dynamic epigenetic modifications, we demonstrate that regulation of pluripotency and differentiation markers in healthy intestinal mucosa involves different and specific epigenetic mechanisms.

Transcription factors GATA4 and HNF4A control distinct aspects of intestinal homeostasis in conjunction with transcription factor CDX2

Distinct groups of transcription factors (TFs) assemble at tissue-specific cis-regulatory sites, implying that different TF combinations may control different genes and cellular functions. Within such combinations, TFs that specify or maintain a lineage and are therefore considered master regulators may play a key role. Gene enhancers often attract these tissue-restricted TFs, as well as TFs that are expressed more broadly. However, the contributions of the individual TFs to combinatorial regulatory activity have not been examined critically in many cases in vivo. We address this question using a genetic approach in mice to inactivate the intestine-specifying and intestine-restricted factor CDX2 alone or in combination with its more broadly expressed partner factors, GATA4 and HNF4A. Compared with single mutants, each combination produced significantly greater defects and rapid lethality through distinct anomalies. Intestines lacking Gata4 and Cdx2 were deficient in crypt cell replication, whereas combined loss of Hnf4a and Cdx2 specifically impaired viability and maturation of villus enterocytes. Integrated analysis of TF binding and of transcripts affected in Hnf4a;Cdx2 compound-mutant intestines indicated that this TF pair controls genes required to construct the apical brush border and absorb nutrients, including dietary lipids. This study thus defines combinatorial TF activities, their specific requirements during tissue homeostasis, and modules of transcriptional targets in intestinal epithelial cells in vivo.

Comparison of bioactivities of talactoferrin and lactoferrins from human and bovine milk

OBJECTIVES

Lactoferrin (Lf) is an iron-binding glycoprotein present in high concentration in human milk. It is a pleiotropic protein and is involved in diverse bioactivities, such as stimulation of cell proliferation and differentiation, immune competence, antimicrobial activities, anti-infection, and anticancer activities. Lf has been shown to be partly resistant to proteolysis in the gastrointestinal tract and may thus play important roles in the intestine and liver during infancy. Talactoferrin alfa (TLf) is a recombinant human Lf shown to protect against sepsis and necrotizing enterocolitis as well as cancer. Because bovine Lf (bLf) and human Lf have different amino acid composition and all 3 Lfs differ in glycosylation, they may have different functions/potency. The objective of the present study was to investigate and compare bioactivities of TLf and Lfs from human and bovine milk and thus to provide a better understanding of the bioactivities of different forms of Lf and their potential applications.

METHODS

In the present study, Caco-2 and C3A cells were used as intestine and liver models to evaluate internalization of Lfs by intestine and liver cells, effects of Lfs on cell proliferation and differentiation, growth of enteropathogenic Escherichia coli (EPEC), chemokine (C-C motif) ligand 20 (CCL20) secretion, and transforming growth factor (TGF)-β1 expression. In addition, HT-29 cells were used as a colon cancer cell model to examine the effects of Lfs on apoptosis.

RESULTS

All Lfs significantly enhanced cell proliferation and differentiation, apoptosis, CCL20 secretion, and TGF-β1 expression. They also markedly suppressed growth of EPEC. Compared with bLf, TLf showed stronger effects on suppression of EPEC growth and enhancement of TGF-β1 secretion, whereas bLf exhibited more potent effects on cell differentiation, apoptosis, and CCL20 secretion.

CONCLUSIONS

Our results demonstrate that TLf has several bioactivities similar to human Lf and bLf from milk and may play critical roles in immune and intestinal development in infants as well as having anti-cancer activities in adults. TLf and bLf may be used for different applications owing to their various potencies. TLf may preferentially be used for anti-bacterial applications, whereas bLf may be used for cancer therapy because it exhibits stronger effects on CCL20 secretion, cell differentiation, and apoptosis.

Induction of histone H3K4 methylation at the promoter, enhancer, and transcribed regions of the Si and Sglt1 genes in rat jejunum in response to a high-starch/low-fat diet

OBJECTIVE

Histone methylation patterns are associated with various aspects of biology, including transcriptional regulation. Methylation of histone H3 at lysine 4 (H3K4) leads to transcriptional activation through recruitment of transcription activation complexes onto target genes; in contrast, methylation of histone H3K9, or histone H4K20, leads to transcriptional inactivation attracting heterochromatin protein 1 (HP1). It is not yet known whether jejunal induction of sucrase-isomaltase (Si) and sodium-dependent glucose cotransporter (Sglt1) genes by intake of a high-starch/low-fat diet in rats is regulated by coordinated changes of these histone methylation events. In the present study, we investigated whether these histone modifications at the promoter, enhancer, and transcribed regions of Si and Sglt1 genes in rat jejunum are affected by consumption of a high-starch/low-fat diet.

METHODS

Chromatin immunoprecipitation assays using antibodies against methylated-histone H3K4, H3K9, H4K20, and HP1 were performed at various regions associated with the Si and Sglt1 genes in jejunum of rats fed a high-starch/low-fat diet or a low-starch/high-fat diet for 7 d.

RESULTS

Feeding rats the high-starch/low-fat diet induced mono-, di-, and trimethylation of histone H3K4 on the promoter and transcribed regions of the Si and Sglt1 genes. In contrast, methylation of histones H3K9 and H4K20, and binding of HP1 at these gene regions, were not affected by the high-starch/low-fat diet.

CONCLUSION

These observations suggest that induction of Si and Sglt1 gene expression in rat jejunum by a high-starch/low-fat diet intake is positively associated with histone H3K4 methylation, but not with histone H3K9/H4K20 methylation, or with binding of HP1.

DNA methylation is required for the control of stem cell differentiation in the small intestine

There is a tight correlation between the epigenetic status of genes and expression changes during differentiation. Sheaffer et al. used acute deletion of Dnmt1 to reduce DNA methylation maintenance in the intestinal epithelium. This caused crypt expansion and decreased differentiation. DNA methylation was dynamic at enhancers during the rapid transition from stem to differentiated epithelial cells. These findings reveal that the loss of DNA methylation at intestinal stem cell gene enhancers causes inappropriate gene expression and delayed differentiation.

The mammalian intestinal epithelium has a unique organization in which crypts harboring stem cells produce progenitors and finally clonal populations of differentiated cells. Remarkably, the epithelium is replaced every 3–5 d throughout adult life. Disrupted maintenance of the intricate balance of proliferation and differentiation leads to loss of epithelial integrity or barrier function or to cancer. There is a tight correlation between the epigenetic status of genes and expression changes during differentiation; however, the mechanism of how changes in DNA methylation direct gene expression and the progression from stem cells to their differentiated descendants is unclear. Using conditional gene ablation of the maintenance methyltransferase Dnmt1, we demonstrate that reducing DNA methylation causes intestinal crypt expansion in vivo. Determination of the base-resolution DNA methylome in intestinal stem cells and their differentiated descendants shows that DNA methylation is dynamic at enhancers, which are often associated with genes important for both stem cell maintenance and differentiation. We establish that the loss of DNA methylation at intestinal stem cell gene enhancers causes inappropriate gene expression and delayed differentiation.

Modulation of stemness in a human normal intestinal epithelial crypt cell line by activation of the WNT signaling pathway

The small intestine consists of two histological compartments composed of the crypts and the villi. The function of the adult small intestinal epithelium is mediated by four different types of mature cells: enterocytes, goblet, enteroendocrine and Paneth. Undifferentiated cells reside in the crypts and produce these four types of mature cells. The niche-related Wnt and Bmp signaling pathways have been suggested to be involved in the regulation and maintenance of the stem cell microenvironment. In our laboratory, we isolated the first normal human intestinal epithelial crypt (HIEC) cell model from the human fetal intestine and in this study we investigated the expression of a panel of intestinal stem cell markers in HIEC cells under normal culture parameters as well as under conditions that mimic the stem cell microenvironment. The results showed that short term stimulation of HIEC cells with R-spondin 1 and Wnt-3a±SB-216763, a glycogen synthase kinase 3β (GSK3β) inhibitor, induced β-catenin/TCF activity and expression of the WNT target genes, cyclin D2 and LGR5. Treatment of HIEC cells with noggin, an antagonist of BMP signaling, abolished SMAD2/5/8 phosphorylation. Inducing a switch from inactive WNT/active BMP toward active WNT/inactive BMP pathways was sufficient to trigger a robust intestinal primordial stem-like cell signature with predominant LGR5, PHLDA1, PROM1, SMOC2 and OLFM4 expression. These findings demonstrate that even fully established cultures of intestinal cells can be prompted toward a CBC stem cell-like phenotype. This model should be useful for studying the regulation of human intestinal stem cell self-renewal and differentiation.

Enterocyte-specific regulation of the apical nutrient transporter SLC6A19 (B(0)AT1) by transcriptional and epigenetic networks

Enterocytes are specialized to absorb nutrients from the lumen of the small intestine by expressing a select set of genes to maximize the uptake of nutrients. They develop from stem cells in the crypt and differentiate into mature enterocytes while moving along the crypt-villus axis. Using the Slc6a19 gene as an example, encoding the neutral amino acid transporter B(0)AT1, we studied regulation of the gene by transcription factors and epigenetic factors in the intestine. To investigate this question, we used a fractionation method to separate mature enterocytes from crypt cells and analyzed gene expression. Transcription factors HNF1a and HNF4a activate transcription of the Slc6a19 gene in villus enterocytes, whereas high levels of SOX9 repress expression in the crypts. CpG dinucleotides in the proximal promoter were highly methylated in the crypt and fully de-methylated in the villus. Furthermore, histone modification H3K27Ac, indicating an active promoter, was prevalent in villus cells but barely detectable in crypt cells. The results suggest that Slc6a19 expression in the intestine is regulated at three different levels involving promoter methylation, histone modification, and opposing transcription factors.

Laminin receptor 37/67LR regulates adhesion and proliferation of normal human intestinal epithelial cells

Interactions between the cell basal membrane domain and the basement membrane are involved in several cell functions including proliferation, migration and differentiation. Intestinal epithelial cells can interact with laminin, a major intestinal basement membrane glycoprotein, via several cell-surface laminin-binding proteins including integrin and non-integrin receptors. The 37/67kDa laminin receptor (37/67LR) is one of these but its role in normal epithelial cells is still unknown. The aim of this study was to characterise the expression pattern and determine the main function of 37/67LR in the normal human small intestinal epithelium. Immunolocalization studies revealed that 37/67LR was predominantly present in the undifferentiated/proliferative region of the human intestinal crypt in both the immature and adult intestine. Using a human intestinal epithelial crypt (HIEC) cell line as experimental model, we determined that 37/67LR was expressed in proliferative cells in both the cytoplasmic and membrane compartments. Small-interfering RNA-mediated reduction of 37/67LR expression led to HIEC cell-cycle reduction and loss of the ability to adhere to laminin-related peptides under conditions not altering ribosomal function. Taken together, these findings indicate that 37/67LR regulates proliferation and adhesion in normal intestinal epithelial cells independently of its known association with ribosomal function.

Inhibition of PRC2 histone methyltransferase activity increases TRAIL-mediated apoptosis sensitivity in human colon cancer cells

Colorectal cancer is ranked among the top leading causes of cancer death in industrialized populations. Polycomb group proteins, including Suz12 and Ezh2, are epigenetic regulatory proteins that act as transcriptional repressors of many differentiation-associated genes and are overexpressed in a large subset of colorectal cancers. Retinoic acid (RA) acts as a negative regulator of PcG actions in stem cells, but has shown limited therapeutic potential in some solid tumors, including colorectal cancer, in part because of retinoic acid receptor β silencing. Through treatment with RA, Suz12 shRNA knockdown, or Ezh2 pharmacological inhibition with 3-deazaneplanocin A (DZNep), we increased TRAIL-mediated apoptosis in human colorectal cancer cell lines. This increased apoptosis in human colon cancer cells after RA or DZNep treatment was associated with a ~2.5-fold increase in TNFRSF10B (DR5) transcript levels and a 42% reduction in the H3K27me3 epigenetic mark at the TNFRSF10B promoter after DZNep addition. Taken together, our findings indicate that pharmacological inhibition of Polycomb repressive complex 2 histone methyltransferase activity may constitute a new epigenetic therapeutic strategy to overcome RA non-responsiveness in a subset of colorectal tumors by increasing TRAIL-mediated apoptosis sensitivity.

Circadian regulation of epithelial functions in the intestine

Many physiological functions exhibit a diurnal rhythmicity that is influenced by biological clocks and feeding rhythms. In this review, we discuss the growing evidence showing the important role of circadian rhythms in regulating intestinal mucosa. First, we introduce the molecular timing system and the interrelationship between the master biological clock in the suprachiasmatic nuclei of the brain and the peripheral intestinal clock and provide evidence that the intestinal clock is entrained with the external environment. Second, we review the circadian rhythmicity of enterocyte proliferation and the largely unknown regulatory mechanisms behind these rhythms. Finally, we focus on the circadian clock control of food processing that functions by regulating the expression of digestive enzymes and intestinal nutrient and salt transporters. The concepts to be discussed highlight the ability of the intestinal epithelium to utilize self-sustained clock signals together with signals associated with changes in the cellular environment and to use endogenous temporal control of the gastrointestinal functions to meet varying physiological and pathophysiological demands. The fact that internal de-synchronizations within the body, such as those that occur in shift workers or with changes in food intake behaviour, are often associated with malfunctions of the gastrointestinal tract indicates that more information about the connections between the circadian clock and intestinal mucosa/transporting enterocytes could provide clues for future therapies.

Pharmacological inhibition of polycomb repressive complex-2 activity induces apoptosis in human colon cancer stem cells

Colorectal cancer is among the leading causes of cancer death in the USA. The polycomb repressive complex 2 (PRC2), including core components SUZ12 and EZH2, represents a key epigenetic regulator of digestive epithelial cell physiology and was previously shown to promote deleterious effects in a number of human cancers, including colon. Using colon cancer stem cells (CCSC) isolated from human primary colorectal tumors, we demonstrate that SUZ12 knockdown and treatment with DZNep, one of the most potent EZH2 inhibitors, increase apoptosis levels, marked by decreased Akt phosphorylation, in CCSCs, while embryonic stem (ES) cell survival is not affected. Moreover, DZNep treatments lead to increased PTEN expression in these highly tumorigenic cells. Taken together, our findings suggest that pharmacological inhibition of PRC2 histone methyltransferase activity may constitute a new, epigenetic therapeutic strategy to target highly tumorigenic and metastatic colon cancer stem cells.

The junctional proteins cingulin and paracingulin modulate the expression of tight junction protein genes through GATA-4

The cytoplamic junctional proteins cingulin and paracingulin have been implicated in the regulation of gene expression in different cultured cell models. In renal epithelial MDCK cells, depletion of either protein results in a Rho-dependent increase in the expression of claudin-2. Here we examined MDCK cell clones depleted of both cingulin and paracingulin (double-KD cells), and we found that unexpectedly the expression of claudin-2, and also the expression of ZO-3 and claudin-3, were decreased, while RhoA activity was still higher than in control cells. The decreased expression of claudin-2 and other TJ proteins in double–KD cells correlated with reduced levels of the transcription factor GATA-4, and was rescued by overexpression of GATA-4, but not by inhibiting RhoA activity. These results indicate that in MDCK cells GATA-4 is required for the expression of claudin-2 and other TJ proteins, and that maintenance of GATA-4 expression requires either cingulin or paracingulin. These results and previous studies suggest a model whereby cingulin and paracingulin redundantly control the expression of specific TJ proteins through distinct GATA-4- and RhoA-dependent mechanisms, and that in the absence of sufficient levels of GATA-4 the RhoA-mediated upregulation of claudin-2 is inhibited.

Src family kinase inhibitor PP2 accelerates differentiation in human intestinal epithelial cells

The proto-oncogene Src is an important protein tyrosine kinase involved in signaling pathways that control cell adhesion, growth, migration and survival. Here, we investigated the involvement of Src family kinases (SFKs) in human intestinal cell differentiation. We first observed that Src activity peaked in early stages of Caco-2/15 cell differentiation. Inhibition of SFKs with PP2, a selective SFK inhibitor, accelerated the overall differentiation program. Interestingly, all polarization and terminal differentiation markers tested, including sucrase-isomaltase, lactase-phlorizin hydrolase and E and Li-cadherins were found to be significantly up-regulated after only 3 days of treatment in the newly differentiating cells. Further investigation of the effects of PP2 revealed a significant up-regulation of the two main intestinal epithelial cell-specific transcription factors Cdx2 and HNF1α and a reduction of polycomb PRC2-related epigenetic repressing activity as measured by a decrease in H3K27me3, two events closely related to the control of cell terminal differentiation in the intestine. Taken together, these data suggest that SFKs play a key role in the control of intestinal epithelial cell terminal differentiation.

CDX2 is an amplified lineage-survival oncogene in colorectal cancer

The mutational activation of oncogenes drives cancer development and progression. Classic oncogenes, such as MYC and RAS, are active across many different cancer types. In contrast, "lineage-survival" oncogenes represent a distinct and emerging class typically comprising transcriptional regulators of a specific cell lineage that, when deregulated, support the proliferation and survival of cancers derived from that lineage. Here, in a large collection of colorectal cancer cell lines and tumors, we identify recurrent amplification of chromosome 13, an alteration highly restricted to colorectal-derived cancers. A minimal region of amplification on 13q12.2 pinpoints caudal type homeobox transcription factor 2 (CDX2), a regulator of normal intestinal lineage development and differentiation, as a target of the amplification. In contrast to its described role as a colorectal tumor suppressor, CDX2 when amplified is required for the proliferation and survival of colorectal cancer cells. Further, transcriptional profiling, binding-site analysis, and functional studies link CDX2 to Wnt/β-catenin signaling, itself a key oncogenic pathway in colorectal cancer. These data characterize CDX2 as a lineage-survival oncogene deregulated in colorectal cancer. Our findings challenge a prevailing view that CDX2 is a tumor suppressor in colorectal cancer and uncover an additional piece in the multistep model of colorectal tumorigenesis.

RGD-Dependent Epithelial Cell-Matrix Interactions in the Human Intestinal Crypt

Interactions between the extracellular matrix (ECM) and integrin receptors trigger structural and functional bonds between the cell microenvironment and the cytoskeleton. Such connections are essential for adhesion structure integrity and are key players in regulating transduction of specific intracellular signals, which in turn regulate the organization of the cell microenvironment and, consequently, cell function. The RGD peptide-dependent integrins represent a key subgroup of ECM receptors involved in the maintenance of epithelial homeostasis. Here we review recent findings on RGD-dependent ECM-integrin interactions and their roles in human intestinal epithelial crypt cells.

Constitutive expression of an antioxidant enzyme, glutathione S-transferase P1, during differentiation of human intestinal Caco-2 cells

In this study, we investigated the molecular mechanism of the constitutive expression of an antioxidant enzyme, glutathione S-transferase (GST), during differentiation of human intestinal epithelial Caco-2 cells. We observed that the class π GST isozyme (GST P1) expression correlated with the increased expression of caudal-related homeodomain protein 2 (CDX2), a member of the mammalian homeobox family of transcription factors. In addition, transfection of Caco-2 cells with the human CDX2 cDNA resulted in enhanced expression of the GST P1 gene and protein. Chromatin immunoprecipitation assay demonstrated that CDX2 binds to the GST P1 promoter containing the putative consensus CDX-binding element, TTTAC, located at -247 upstream from the established site for transcription initiation. Using the dsDNA pull-down assay, it was revealed that CDX2 recognized and bound to the putative consensus CDX-binding element within the human GST P1 promoter region and that the amount of the CDX2 bound to the putative consensus CDX-binding element increased during Caco-2 cell differentiation. Furthermore, we demonstrated that CDX2 formed the transcriptional complex with Sp1 and bound to the putative consensus CDX-binding element within the human GST P1 promoter region. These data suggest that CDX2 binds to the human GST P1 promoter via complex formation with Sp1 and controls the constitutive expression of GST P1 during Caco-2 cell differentiation.

Autophagy is active in normal colon mucosa

Recently, autophagy has been found to be strongly activated in colon cancer cells, but few studies have addressed the normal colon mucosa. The aim of this study was to characterize autophagy in normal human intestinal cells. We used the expression of LC3-II and BECN1 as well as SQSTM1 as markers of autophagy activity. Using the normal human intestinal epithelial crypt (HIEC) cell experimental model, we found that autophagy was much more active in undifferentiated cells than in differentiated cells. In the normal adult colonic mucosa, BECN1 was found in the proliferative epithelial cells of the lower part of the gland while SQSTM1 was predominantly found in the differentiated cells of the upper part of the gland and surface epithelium. Interestingly, the weak punctate pattern of SQSTM1 expression in the lower gland colocalized with BECN1-labeled autophagosomes. The usefulness of SQSTM1 as an active autophagy marker was confirmed in colon cancer specimens at the protein and transcript levels. In conclusion, our results show that autophagy is active in the colonic gland and is associated with the intestinal proliferative/undifferentiated and progenitor cell populations.