Regulatory regions driving developmental and tissue-specific expression of the essential pancreatic gene pdx1.

Gannon M, Gamer LW, Wright CV
Dev Biol. 2001 238 (1): 185-201

PMID: 11784003 · DOI:10.1006/dbio.2001.0359

pdx1 (pancreatic and duodenal homeobox gene-1), which is expressed broadly in the embryonic pancreas and, later, in a more restricted manner in the mature beta cells in the islets of Langerhans, is essential both for organ formation and beta cell gene expression and function. We carried out a transgenic reporter gene analysis to identify region- and cell type-specific regulatory regions in pdx1. A 14.5-kb pdx1 genomic fragment corrected the glucose intolerance of pdx1(+/-) animals but, moreover, fully rescued the severe gut and pancreas defects in pdx1(-/-) embryos. Sequences sufficient to direct reporter expression to the entire endogenous pdx1 expression domain lie within 4.3 kb of 5' flanking DNA. In this region, we identified two distinct fragments that drive reporter gene expression to different sets of islet neuroendocrine cells. One shows pan-endocrine cell specificity, the other is selectively activated in insulin-producing beta cells. The endocrine-specific regulatory regions overlap a localized region of 5' flanking DNA that is remarkably conserved in sequence between vertebrate pdx1 genes, and which has been associated with beta cell-selective expression in cultured cell lines. This region contains potential binding sites for several transcription factors implicated in endodermal development and the pathogenesis of some forms of type-2 diabetes. These results are consistent with our previous proposal that conserved upstream pdx1 sequences exert control over pdx1 during embryonic organogenesis and islet endocrine cell differentiation. We propose that mutations affecting the expression and/or activity of transcription factors operating via these sequences may predispose towards diabetes, at least in part by direct effects on endocrine pdx1 expression.

Copyright 2001 Academic Press.

MeSH Terms (29)

Alleles Animals Binding Sites Blotting, Western Cells, Cultured Diabetes Mellitus, Type 2 Endoderm Female Gene Expression Regulation, Developmental Genes, Reporter Genetic Predisposition to Disease Heterozygote Homeodomain Proteins Humans Islets of Langerhans Lac Operon Male Mice Mice, Transgenic Models, Genetic Mutation Pancreas Protein Structure, Tertiary Sex Factors Time Factors Tissue Distribution Trans-Activators Transcription Factors Transgenes

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