Adrian Kee Keong Teo1,5,6,7, Norihiro Tsuneyoshi1, Shawn Hoon2, Ee Kim Tan1, Lawrence W. Stanton3, Christopher V.E. Wright4 and N. Ray Dunn1.
1 Institute of Medical Biology, A*STAR (Agency for Science, Technology and Research), 8A Biomedical Grove, #06-06 Immunos, Singapore 138648, Singapore.
2 Molecular Engineering Lab, A*STAR, 61 Biopolis Drive, Proteos #03-13, Singapore 138673, Singapore.
3 Genome Institute of Singapore, A*STAR, 60 Biopolis Street, #02-01 Genome, Singapore 138672, Singapore.
4 Department of Cell and Developmental Biology and Vanderbilt University Program in Developmental Biology, Vanderbilt University Medical Center, 3144 MRBIII, 465 21st Avenue South, Nashville, TN 37232, USA.
5 Present address: Discovery Research Division, Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Proteos #06-07, Singapore 138673, Singapore
6 Present affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.
7 Present affiliation: Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore.
Published in: Stem Cell Reports Vol 4 :1–13, April 14, 2015
Inactivation of the Pancreatic and Duodenal Homeobox 1 (PDX1) gene causes pancreatic agenesis, which places PDX1 high atop the regulatory network controlling development of this indispensable organ. However, little is known about the identity of PDX1 transcriptional targets. We simulated pancreatic development by differentiating human embryonic stem cells (hESCs) into early pancreatic progenitors and subjected this cell population to PDX1 chromatin immunoprecipitation sequencing (ChIP-seq). We identified more than 350 genes bound by PDX1, whose expression was upregulated on day 17 of differentiation. This group included known PDX1 targets and many genes not previously linked to pancreatic development. ChIP-seq also revealed PDX1 occupancy at hepatic genes.We hypothesized that simultaneous PDX1-driven activation of pancreatic and repression of hepatic programs underlie early divergence between pancreas and liver. In HepG2 cells and differentiating hESCs, we found that PDX1 binds and suppresses expression of endogenous liver genes. These findings rebrand PDX1 as a context-dependent transcriptional repressor and activator within the same cell type.
PDX1 represses liver marker genes. (A) AFP and PDX1 immunostaining on day 17 of pancreatic differentiation. AFP and PDX1 label distinct cell populations that are often observed in close proximity. Scale bar represents 100 μm. (B) Western blot analyses for PDX1 and AFP on days 0 and 17 of pancreatic differentiation in GFP- or human PDX1-overexpressing hESC clones.
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