CCAAT/enhancer binding protein-mediated regulation of TGFβ receptor 2 expression determines the hepatoblast fate decision

Human embryonic stem cells (hESCs) and their derivatives are expected to be used in drug discovery, regenerative medicine and the study of human embryogenesis. Because hepatocyte differentiation from hESCs has the potential to recapitulate human liver development in vivo, we employed this differentiation method to investigate the molecular mechanisms underlying human hepatocyte differentiation. A previous study has shown that a gradient of transforming growth factor beta (TGF beta) signaling is required to segregate hepatocyte and cholangiocyte lineages from hepatoblasts. Although CCAAT/enhancer binding proteins (c/EBPs) are known to be important transcription factors in liver development, the relationship between TGF beta signaling and c/EBP-mediated transcriptional regulation in the hepatoblast fate decision is not well known. To clarify this relationship, we examined whether c/EBPs could determine the hepatoblast fate decision via regulation of TGF beta receptor 2 (TGFBR2) expression in the hepatoblast-like cells differentiated from hESCs. We found that TGFBR2 promoter activity was negatively regulated by c/EBP alpha and positively regulated by c/EBP beta. Moreover, c/EBP alpha overexpression could promote hepatocyte differentiation by suppressing TGFBR2 expression, whereas c/EBP beta overexpression could promote cholangiocyte differentiation by enhancing TGFBR2 expression. Our findings demonstrated that c/EBP alpha and c/EBP beta determine the lineage commitment of hepatoblasts by negatively and positively regulating the expression of a common target gene, TGFBR2, respectively.