Hepatocyte nuclear factor 3beta is involved in pancreatic beta-cell-specific transcription of the pdx-1 gene.
The mammalian homeobox gene pdx-1 is expressed in pluripotent precursor cells in the dorsal and ventral pancreatic bud and duodenal endoderm, which will produce the pancreas and the rostral duodenum. In the adult, pdr-1 is expressed principally within insulin-secreting pancreatic islet beta cells and cells of the duodenal epithelium. Our objective in this study was to localize sequences within the mouse pdx-1 gene mediating selective expression within the islet. Studies of transgenic mice in which a genomic fragment of the mouse pdx-1 gene from kb -4.5 to +8.2 was used to drive a beta-galactosidase reporter showed that the control sequences sufficient for appropriate developmental and adult specific expression were contained within this region. Three nuclease-hypersensitive sites, located between bp -2560 and -1880 (site 1), bp -1330 and -800 (site 2), and bp -260 and +180 (site 3), were identified within the 5'-flanking region of the endogenous pdx-1 gene. Pancreatic beta-cell-specific expression was shown to be controlled by sequences within site 1 from an analysis of the expression pattern of various pdr-1-herpes simplex virus thymidine kinase promoter expression constructs in transfected beta-cell and non-beta-cell lines. Furthermore, we also established that this region was important in vivo by demonstrating that expression from a site 1-driven beta-galactosidase reporter construct was directed to islet beta-cells in transgenic mice. The activity of the site 1-driven constructs was reduced substantially in beta-cell lines by mutating a hepatocyte nuclear factor 3 (HNF3)-like site located between nucleotides -2007 and -1996. Gel shift analysis indicated that HNF3beta present in islet beta cells binds to this element. Immunohistochemical studies revealed that HNF3beta was present within the nuclei of almost all islet beta cells and subsets of pancreatic acinar cells. Together, these results suggest that HNF3beta, a key regulator of endodermal cell lineage development, plays an essential role in the cell-type-specific transcription of the pdx-1 gene in the pancreas.
Wu
K L
KL
Department of Molecular Physiology and Biophysics, Vanderbilt Medical Center, Nashville, Tennessee 37232, USA.
Gannon
M
M
Peshavaria
M
M
Offield
M F
MF
Henderson
E
E
Ray
M
M
Marks
A
A
Gamer
L W
LW
Wright
C V
CV
Stein
R
R
D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D051542:Hepatocyte Nuclear Factor 3-beta; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007515:Islets of Langerhans / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000378:metabolism*; D009928:Organ Specificity; D010179:Pancreas / Q000737:chemistry / Q000166:cytology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011993:Recombinant Fusion Proteins; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics
D004268:DNA-Binding Proteins; C496502:FOXA2 protein, human; C496503:Foxa2 protein, mouse; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein; D051542:Hepatocyte Nuclear Factor 3-beta; D004247:DNA