title: Mice lacking myosin IXb, an inflammatory bowel disease susceptibility gene, have impaired intestinal barrier function and superficial ulceration in the ileum.
abstract: Genetic studies have implicated MYO9B, which encodes myosin IXb (Myo9b), a motor protein with a Rho GTPase activating domain (RhoGAP), as a susceptibility gene for inflammatory bowel disease (IBD). Moreover, we have recently shown that knockdown of Myo9b in an intestinal epithelial cell line impairs wound healing and barrier function. Here, we investigated whether mice lacking Myo9b have impaired intestinal barrier function and features of IBD. Myo9b knock out (KO) mice exhibit impaired weight gain and fecal occult blood (indicator of gastrointestinal bleeding), and increased intestinal epithelial cell apoptosis could be detected along the entire intestinal axis. Histologic analysis revealed intestinal mucosal damage, most consistently observed in the ileum, which included superficial ulceration and neutrophil infiltration. Focal lesions contained neutrophils and ultrastructural examination confirmed epithelial discontinuity and the deposition of extracellular matrix. We also observed impaired mucosal barrier function in KO mice. Transepithelial electrical resistance of KO ileum is >3 fold less than WT ileum. The intestinal mucosa is also permeable to high molecular weight dextran, presumably due to the presence of mucosal surface ulcerations. There is loss of tight junction-associated ZO-1, decreased lateral membrane associated E-cadherin, and loss of terminal web associated cytokeratin filaments. Consistent with increased Rho activity in the KO, there is increased subapical expression of activated myosin II (Myo2) based on localization of phosphorylated Myo2 regulatory light chain. Except for a delay in disease onset in the KO, no difference in dextran sulfate sodium-induced colitis and lethality was observed between wild-type and Myo9b KO mice.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Hegan
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut.
authors.forename: Surjit K
authors.initials: SK
authors.lastname: Chandhoke
authors.affiliation: Department of Respiratory Medicine, Yale School of Medicine, New Haven, Connecticut.
authors.forename: Christina
authors.initials: C
authors.lastname: Barone
authors.affiliation: Department of Respiratory Medicine, Yale School of Medicine, New Haven, Connecticut.
authors.forename: Marie
authors.initials: M
authors.lastname: Egan
authors.affiliation: Institute of Molecular Cell Biology, Westfalian Wilhelms University, Münster, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bähler
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut.|Departments of Cell Biology and Pathology, Yale School of Medicine, New Haven, Connecticut.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Mooseker
mesh_terms: D000818:Animals; D006801:Humans; D007082:Ileum / Q000473:pathology*; D015212:Inflammatory Bowel Diseases / Q000235:genetics* / Q000473:pathology; D007422:Intestines / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D024462:Myosin Type II / Q000378:metabolism*
chemical_list: D024462:Myosin Type II
keywords: DSS; ROCK; Rho GAP; myosin II; tight junction