Pdx-1 is not sufficient for repression of proglucagon gene transcription in islet or enteroendocrine cells. Endocrinology 146

Pdx-1 plays a key role in the development of the pancreas and the control of islet gene transcription and has also been pro-posedasadominant regulator of the- vs.-cell phenotypevia extinction of proglucagon expression. To ascertain the rela-tionship between Pdx-1 and proglucagon gene expression, we examined the effect of enhanced pdx-1 expression on proglu-cagon gene expression in murine islet TC-1 and GLUTag enteroendocrine cells. Although adenoviral transduction in-creased the levels of pdx-1 mRNA transcripts and nuclear Pdx-1 protein, overexpression of pdx-1 did not repress endog-enous proglucagon gene expression in TC-1 or GLUTag cells ormurine islets. Immunohistochemical analysis of cells trans-duced with Ad-pdx-1 demonstrated multiple individual islet or enteroendocrine cells exhibiting both nuclear Pdx-1 and cytoplasmic glucagon-like peptide-1 immunopositivity. Th