title: Mouse Paneth cell antimicrobial function is independent of Nod2.
abstract: OBJECTIVE
  Although polymorphisms of the NOD2 gene predispose to the development of ileal Crohn's disease, the precise mechanisms of this increased susceptibility remain unclear. Previous work has shown that transcript expression of the Paneth cell (PC) antimicrobial peptides (AMPs) α-defensin 4 and α-defensin-related sequence 10 are selectively decreased in Nod2(-/-) mice. However, the specific mouse background used in this previous study is unclear. In light of recent evidence suggesting that mouse strain strongly influences PC antimicrobial activity, we sought to characterise PC AMP function in commercially available Nod2(-/-) mice on a C57BL/6 (B6) background. Specifically, we hypothesised that Nod2(-/-) B6 mice would display reduced AMP expression and activity.
  
  
  METHODS
  Wild-type (WT) and Nod2(-/-) B6 ileal AMP expression was assessed via real-time PCR, acid urea polyacrylamide gel electrophoresis and mass spectrometry. PCs were enumerated using flow cytometry. Functionally, α-defensin bactericidal activity was evaluated using a gel-overlay antimicrobial assay. Faecal microbial composition was determined using 454-sequencing of the bacterial 16S gene in cohoused WT and Nod2(-/-) littermates.
  
  
  RESULTS
  WT and Nod2(-/-) B6 mice displayed similar PC AMP expression patterns, equivalent α-defensin profiles, and identical antimicrobial activity against commensal and pathogenic bacterial strains. Furthermore, minimal differences in gut microbial composition were detected between the two cohoused, littermate mouse groups.
  
  
  CONCLUSIONS
  Our data reveal that Nod2 does not directly regulate PC antimicrobial activity in B6 mice. Moreover, we demonstrate that previously reported Nod2-dependent influences on gut microbial composition may be overcome by environmental factors, such as cohousing with WT littermates.
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill, , Chapel Hill, North Carolina, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Shanahan
authors.forename: Ian M
authors.initials: IM
authors.lastname: Carroll
authors.forename: Emily
authors.initials: E
authors.lastname: Grossniklaus
authors.forename: Andrew
authors.initials: A
authors.lastname: White
authors.forename: Richard J
authors.initials: RJ
authors.lastname: von Furstenberg
authors.forename: Roshonda
authors.initials: R
authors.lastname: Barner
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Fodor
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Henning
authors.forename: R Balfour
authors.initials: RB
authors.lastname: Sartor
authors.forename: Ajay S
authors.initials: AS
authors.lastname: Gulati
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D023082:Defensins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects; D005243:Feces / Q000382:microbiology*; D007082:Ileum / Q000166:cytology / Q000378:metabolism*; D037181:Lectins, C-Type / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008826:Microbial Sensitivity Tests; D009113:Muramidase / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism*; D000073718:Pancreatitis-Associated Proteins; D019879:Paneth Cells / Q000166:cytology / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D012259:Ribonuclease, Pancreatic / Q000235:genetics / Q000378:metabolism; D019779:Salmonella enterica / Q000187:drug effects; D014158:Transcription, Genetic; D023084:alpha-Defensins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C092570:CRS4C protein, mouse; D023082:Defensins; D037181:Lectins, C-Type; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; D000073718:Pancreatitis-Associated Proteins; D010455:Peptides; D011498:Protein Precursors; D012333:RNA, Messenger; D023084:alpha-Defensins; C519253:Ang4 protein, mouse; D012259:Ribonuclease, Pancreatic; D009113:Muramidase; C472773:lysozyme P, mouse
keywords: BACTERIAL INTERACTIONS; CROHN'S DISEASE; IBD - GENETICS; INFLAMMATORY BOWEL DISEASE; INTESTINAL EPITHELIUM