Loss of Hepatocyte-Nuclear-Factor-4a Affects Colonic Ion Transport and Causes Chronic Inflammation Resembling Inflammatory Bowel Disease in Mice Mathieu Darsigny1,2, Jean-Philippe Babeu1,2, Andre´ e-Anne Dupuis1,2, Emma E. Furth3, Ernest G. Seidman1,4, E´ mile Le´ vy1,5, Elena F. Verdu6, Fernand-Pierre Gendron1,2, Fran c¸ois Boudreau1,2* 1 Canadian Institutes of Health Research Team on Digestive Epithelium, De´partement d’anatomie et biologie cellulaire, Faculte´ de Me´decine et des Sciences de la Sante´, Universite´ de Sherbrooke, Sherbrooke, Quebec, Canada, 2 De´partement d’anatomie et biologie cellulaire, Faculte´ de Me´decine et des Sciences de la Sante´, Universite´ de Sherbrooke, Sherbrooke, Quebec, Canada, 3 Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America, 4 Research Institute, McGill University Health Center, Montre´al, Quebec, Canada, 5 Department of Nutrition, CHU Ste-Justine, Universite´ de Montre´al, Quebec, Canada, 6 Division of Gastroenterology, McMaster University, Hamilton, Ontario, Canada Abstract Background: Hnf4a, an epithelial specific transcriptional regulator, is decreased in inflammatory bowel disease and protects against chemically-induced colitis in mice. However, the precise role of this factor in maintaining normal inflammatory homeostasis of the intestine remains unclear. The aim of this study was to evaluate the sole role of epithelial Hnf4a in the maintenance of gut inflammatory homeostasis in mice. Methodology/Principal Findings: We show here that specific epithelial deletion of Hnf4a in mice causes spontaneous chronic intestinal inflammation leading to focal areas of crypt dropout, increased cytokines and chemokines secretion, immune cell infiltrates and crypt hyperplasia. A gene profiling analysis in diseased Hnf4a colon confirms profound genetic changes in cell death and proliferative behaviour related to cancer. Among the genes involved in the immune protection through epithelial barrier function, we identify the ion transporter claudin-15 to be down-modulated early in the colon of Hnf4a mutants. This coincides with a significant decrease of mucosal ion transport but not of barrier permeability in young animals prior to the manifestation of the disease. We confirm that claudin-15 is a direct Hnf4a gene target in the intestinal epithelial context and is down-modulated in mouse experimental colitis and inflammatory bowel disease. Conclusion: Our results highlight the critical role of Hnf4a to maintain intestinal inflammatory homeostasis during mouse adult life and uncover a novel function for Hnf4a in the regulation of claudin-15 expression. This establishes Hnf4a as a mediator of ion epithelial transport, an important process for the maintenance of gut inflammatory homeostasis. Citation: Darsigny M, Babeu J-P, Dupuis A-A, Furth EE, Seidman EG, et al. (2009) Loss of Hepatocyte-Nuclear-Factor-4a Affects Colonic Ion Transport and Causes Chronic Inflammation Resembling Inflammatory Bowel Disease in Mice. PLoS ONE 4(10): e7609. doi:10.1371/journal.pone.0007609 Editor: Stefan Bereswill, Charite´-Universita¨tsmedizin Berlin, Germany Received September 16, 2009; Accepted October 2, 2009; Published October 29, 2009 Copyright: 2009 Darsigny et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the Canadian Institute of Health Research (CIHR) (MOP-89770 to F.B.) and a CIHR team grant (CTP-82942). F.B. and F.P.G. are scholars from the ‘‘Fonds de la Recherche en Sante´ du Que´bec’’ and members of the FRSQ-funded ‘‘Centre de Recherche Clinique E´tienne Lebel’’. E.S. is a recipient of a Canadian Research Chair in Immune-Mediated Gastrointestinal Disorders. M.D. and J.-P.B. are recipients of NSERC fellowships. E. Verdu holds a McMaster University Dept. of Medicine Internal Career Research Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: Francois.Boudreau@usherbrooke.ca Introduction Hepatocyte-nuclear-factor-4a (Hnf4a) was originally identified as an endoderm specific transcriptional regulator detectable in the liver, pancreas and intestine, essential for embryonic development [1]. Conditional genetic removal of Hnf4a function in the liver results in impaired lipid metabolism and gluconeogenesis [2] and disorganization of morphological and functional differentiation in the hepatic epithelium [3]. One critical set of gene products found to be disrupted in hepatocytes that have lost Hnf4a is related to epithelial cell adhesion and junction formation [4]. Thus, Hnf4 a represents a potent transcriptional regulator with a strong impact on endodermal development and metabolism related pathophysiology. HNF4a has recently emerged as being a potential regulator of intestinal epithelial function. In vitro studies suggest that it stimulates intestinal epithelial cell differentiation, resulting in the formation of a tight epithelial barrier [5]. These features are central to the differentiated epithelium to ensure nutrient metabolism [6] and barrier protection against pathogens [7]. Another fundamental characteristic of the epithelial barrier is to regulate appropriate ion selectivity, for which impairment contributes to the manifestation of inflammatory bowel disease (IBD) [8,9]. Hnf4a is important during early embryonic colon development and regulation of genes related to epithelial functions [10]. The intestinal epithelial role of Hnf4a is of less importance when disrupted during post-embryonic development of the gut [11]. Hnf4a is required to protect the epithelium during PLoS ONE | www.plosone.org 1 October 2009 | Volume 4 | Issue 10 | e7609