title: Expression profiling of claudins in the human gastrointestinal tract in health and during inflammatory bowel disease.
abstract: BACKGROUND
  Claudins, being part of the tight junction protein family, partially determine the integrity and paracellular permeability of the intestinal epithelium. The aim of this study was twofold. First, the authors set out to create an overview of claudin mRNA expression along the proximal-distal axis of the healthy human intestine. Second, the authors aimed to analyze expression levels of claudins in patients with active and inactive inflammatory bowel diseases (IBD) such as Crohn's disease or ulcerative colitis (UC).
  
  
  METHODS
  mRNA expression levels of claudins were determined in gastrointestinal biopsies from healthy patients as well as patients diagnosed with IBD using SybrGreen real-time PCR.
  
  
  RESULTS
  Claudins show distinct expression patterns throughout the gastrointestinal tract. Some claudins show a proximal expression pattern, such as CLDN18 which is solely expressed in the stomach, and CLDN2 and -15 that are predominantly expressed in the proximal parts of the gastrointestinal tract. Other claudins, such as CLDN3, -4, -7 and -8, are predominantly expressed in the distal parts of the gastrointestinal tract or show a ubiquitous expression pattern throughout the entire gastrointestinal tract, which is the case for CLDN12. In addition, we show that changes in claudin expression in IBD are dependent on gastrointestinal location and inflammatory activity.
  
  
  CONCLUSIONS
  This study provides detailed mRNA expression patterns of various claudins throughout the human gastrointestinal tract. Analysis of expression levels of claudins in patients with CD, active and inactive UC shows that changes in expression are confined to specific intestinal segments and strongly depend on inflammatory activity.
authors.affiliation: Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre ,  The Netherlands.
authors.forename: Anke L
authors.initials: AL
authors.lastname: Lameris
authors.forename: Sylvie
authors.initials: S
authors.lastname: Huybers
authors.forename: Katri
authors.initials: K
authors.lastname: Kaukinen
authors.forename: Tuula H
authors.initials: TH
authors.lastname: Mäkelä
authors.forename: René J
authors.initials: RJ
authors.lastname: Bindels
authors.forename: Joost G
authors.initials: JG
authors.lastname: Hoenderop
authors.forename: Pasi I
authors.initials: PI
authors.lastname: Nevalainen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D057167:Claudins / Q000235:genetics / Q000378:metabolism*; D003093:Colitis, Ulcerative / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D003424:Crohn Disease / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D057167:Claudins; D020033:Protein Isoforms; D012333:RNA, Messenger