The pancreatic homeodomain transcription factor, IDX-1, appears to be a key regulator of pancreatic development, islet cell differentiation, and insulin gene transcription. The IDX-1 gene is also upregulated during pancreatic regeneration. The hypothesis to be tested is that the beta cell-specific regulation of the IDX-1 gene is mediated by the complex coordinate interactions of several transcription factors on the IDX-1 promoter.
The aims of this proposal are; (1) To identify the cis-acting elements of the mouse IDX-1 gene promoter that are responsible for beta- cell regulated expression. The transcription initiation site(s) will be identified. Mutational analysis of the mouse IDX-1 regulatory region will be performed. Constructs will be assessed in beta cell and non-beta cell islet cell lines using a reporter vector containing the bacterial gene chloramphenical acetyl transferase (CAT). The role of selected cellular signalling pathways in the transcriptional regulation of the IDX-1 gene will be assessed. (2) To characterize the physical and functional interactions between DNA binding proteins and beta-cell regulated elements of the IDX-1 promoter. The DNA binding proteins in beta cells that initiate cell-specific transcription of the IDX-1 gene will be investigated by detailed mutational analysis, DNA footprinting, gel mobility shift assays, and antibody-mediated supershift. The possibility of an autoregulatory loop in which the IDX-1 protein regulates its own promoter will be investigated. If any novel DNA binding activities are identified, an attempt will be made to clone them. Understanding IDX01 gene regulation may be relevant to elucidating the pathogenesis of diabetes mellitus. Careful analysis of the IDX-1 promoter may identify signals that activate IDX-1 gene transcription during development and maintain expression in fully differentiated islet beta-cells. Once identified, these signals might eventually be used to induce formation of pancreatic islets in patients with beta-cell insufficiency. The candidate is completing subspeciality training in Endocrinology at Massachusetts General Hospital and has begun postdoctoral training in the laboratory of Molecular Endocrinology with the mentorship of Dr. Joel Habener. The Endocrine Division at the MGH has a rich history of investigation into the basic mechanisms of endocrine disease. The candidate's immediate career goal is the acquisition of state-of-the-art molecular biological techniques in order to allow her to pursue her long term goal, which is the study of gene regulation in endocrine systems in a setting which permits a limited degree of clinical involvement as well.
