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Wiebe PO, Kormish JD, Roper VT, Fujitani Y, Alston NI, Zaret KS, Wright CV, Stein RW, Gannon M
Ptf1a binds to and activates Area III, a highly conserved region of the Pdx1 promoter that mediates early pancreas-wide Pdx1 expression
Mol Cell Biol (2007) 27:4093-104.
The critical pancreatic transcription factor Pdx1 is expressed throughout the pancreas early, but selectively in insulin-producing beta cells postnatally. Previous studies showed that 5' conserved promoter regions Areas I and II (Pdx1(PB)) direct endocrine cell expression, while an adjacent region (Pdx1(XB)) containing the conserved Area III directs transient beta cell expression. Here we use Cre-mediated lineage tracing to track cells that activated these regions. Pdx1(PB)Cre mediated only endocrine cell recombination, while Pdx1(XB)Cre directed broad and early recombination in the developing pancreas. Also, a reporter transgene containing Areas I-II-III was expressed throughout the E10.5 pancreas, and gradually became beta cell selective, similar to endogenous Pdx1. These data suggested that sequences within Area III mediate early pancreas-wide Pdx1 expression. Area III contains a binding site for PTF1, a transcription factor complex essential for pancreas development. This site contributed to Area III-dependent reporter gene expression in the acinar AR42J cell line, while PTF1 specifically trans-activated Area III-containing reporter expression in a non-pancreatic cell line. Importantly, Ptf1a occupied sequences spanning the endogenous PTF1 site in Area III of E11.5 pancreatic buds. These data strongly suggest that PTF1 is an important early activator of Pdx1 in acinar and endocrine progenitor cells during pancreas development.
Publication Date: 2007-06-01.
Last updated on Saturday, August 22, 2020