Chemokine Signaling and Colitis in Gia2 Deficient Mice

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DESCRIPTION (provided by applicant): Following MSTP-funded MD/ PhD training, residency and board certification in combined Anatomic and Clinical Pathology at Baylor College of Medicine, Dr. Edwards is currently conducting a year-long research fellowship at the University of Michigan. This revised application has been developed in the course of research performed at these two institutions. It address the role of G-protein coupled chemokine signaling in T-cell activation, trafficking, and polarized cytokine production in the Gia2-deficient mouse model of inflammatory bowel disease. Deletion of the G-protein alpha subunit Gia2 in mice produces diffuse colitis which can progress to invasive adenocarcinoma, mimicking human ulcerative colitis. Much evidence suggests a central role for G-protein coupled chemokine signaling in mucosal immunity. Before clincial disease is present, T-cells from Gia2 (-/-) mice spontaneously develop a Th1 phenotype, producing elevated levels of Th1-type cytokines (TNFa, IFNg, and IL12). Two new lines of transgenic mice expressing Gia2 only in CD4+ T-cells or colon epthelium are currently being produced and will be used to investigate the mechanisms whereby Gi alpha subunit- dependent signaling contribute to maintaining balanced T-cell responses to environmental antigen. T-lymphocyte subsets from wildtype, Gia2 (-/-), and transgenic mice as described above will be studied to identify whether they respond normally to Th1- or Th2- skewing conditions. These cells will also be used to determine whether particular Gi alpha subunits selectively couple with chemokine receptors known to be involved in T-cell activation and differentiation. Finally, these cells will be screened for changes in chemokine and chemokine receptor expression patterns using gene array, TagMan, and RPA analysis. The responses seen in vitro will be correlated with the development of disease in the strains of mice. These experiments will provide insight into the specificity with which chemokine receptors couple with individual G-protein alpha subunits, and how the loss of Gia2 may lead to alterations in chemokine signaling that predispose to colitis. This application has the support of outstanding mentors at two institutions, and funding of this application will foster Dr Edwards' continued development as a physician-scientist.