ABSTRACT
Transforming growth factor beta1 (TGFbeta1) is a multifunctional growth factor involved in wound healing, tissue fibrosis, and in the pathogenesis of many syndromic diseases (e.g., Marfan syndrome, Camurati-Engelmann disease) and muscular, neurological, ophthalmic, cardiovascular and immunological disorders, and cancer. Since the generation of Tgfb1 knockout mice, there has been extraordinary progress in understanding its physiological and pathophysiological function. Here, we report the generation of a conditional knockout allele for Tgfb1 in which its exon 6 is flanked with LoxP sites. As proof of principle, we crossed these mice to LckCre transgenic mice and specifically disrupted Tgfb1 in T cells. The results indicate that T-cell-produced TGFbeta1 is required for normal in vivo regulation of peripheral T-cell activation, maintenance of T-cell homeostasis, and suppression of autoimmunity.
Subject(s)
Exons/genetics , Gene Targeting/methods , T-Lymphocytes/metabolism , Transforming Growth Factor beta1/genetics , Alleles , Animals , Cell Count , Female , Flow Cytometry , Gene Expression Profiling , Homeostasis/physiology , Male , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Inbred Strains , Mice, Knockout , Mice, Transgenic , Mutation , Reverse Transcriptase Polymerase Chain Reaction , Spleen/cytology , Spleen/metabolism , T-Lymphocytes/cytology , T-Lymphocytes/immunology , Thymus Gland/cytology , Thymus Gland/metabolism , Transforming Growth Factor beta1/physiologyABSTRACT
Patients with ulcerative colitis are at risk for colon cancer and frequently have microsatellite instability,which, in turn, is usually associated with inactivation of transforming growth factor (TGF) beta signaling. TGF-beta1 deficiency in mice can lead to colon cancer that is preceded by precancerous lesions having submucosal inflammation and hyperplastic crypts. Germ-free TGF-beta1-deficient mice are free of inflammation, hyperplasia, and cancer, but when reintroduced into a Helicobacter hepaticus-containing specific pathogen-free room, these lesions reappear. Because adenoma/carcinoma but not inflammation/hyperplasia is dependent on the genetic backgrounds tested, colitis is required, but not sufficient, for carcinogenesis. This animal model should provide insight into the protective role of TGF-beta1 in early stages of ulcerative colitis-associated human colon cancer.
Subject(s)
Colonic Neoplasms/genetics , Colonic Neoplasms/microbiology , Transforming Growth Factor beta/deficiency , Animals , Colitis, Ulcerative/complications , Colitis, Ulcerative/genetics , Colitis, Ulcerative/microbiology , Colonic Neoplasms/prevention & control , Disease Models, Animal , Female , Genetic Predisposition to Disease , Germ-Free Life , Humans , Male , Mice , Mice, Inbred C3H , Mice, Knockout , Transforming Growth Factor beta/genetics , Transforming Growth Factor beta1ABSTRACT
The ligand specificity of transforming growth factor beta (TGFbeta) in vivo in mouse cardiac cushion epithelial-to-mesenchymal transition (EMT) is poorly understood. To elucidate the function of TGFbeta in cushion EMT, we analyzed Tgfb1(-/-), Tgfb2(-/-), and Tgfb3(-/-) mice between embryonic day (E) 9.5 and E14.5 using both in vitro and in vivo approaches. Atrioventricular (AV) canal collagen gel assays at E9.5 indicated normal EMT in both Tgfb1(-/-) and Tgfb3(-/-) mice. However, analysis of Tgfb2(-/-) AV explants at E9.5 and E10.5 indicated that EMT, but not cushion cell proliferation, was initially delayed but later remained persistent. This was concordant with the observation that Tgfb2(-/-) embryos, and not Tgfb1(-/-) or Tgfb3(-/-) embryos, develop enlarged cushions at E14.5 with elevated levels of well-validated indicators of EMT. Collectively, these data indicate that TGFbeta2, and not TGFbeta1 or TGFbeta3, mediates cardiac cushion EMT by promoting both the initiation and cessation of EMT.