Hepatocyte Nuclear Factor 4 Alpha Promotes Definitive Endoderm Differentiation from Human Induced Pluripotent Stem Cells.

Hepatocyte nuclear factor 4 alpha (HNF4α) is a key transcription factor for liver development. Although HNF4α is necessary for hepatoblast differentiation, the function of HNF4α before the hepatoblast differentiation, such as in definitive endoderm differentiation, is not well known. In addition, it is known that there are nine HNF4α isoforms, but the expression and function of each HNF4α isoform during the definitive endoderm differentiation is also not clear. In this study, we examined the expression pattern of HNF4α and its functions in the definitive endoderm differentiation from human induced pluripotent stem (iPS) cells. We found that the HNF4α-1D isoform expression levels were significantly increased during the definitive endoderm differentiation, while the HNF4α-1A isoform expression levels did not change. Therefore, we further examined the function of the HNF4α-1D isoform in definitive endoderm differentiation. HNF4α-1D overexpression or knockdown was found to promote or prevent the definitive endoderm differentiation, respectively. Interestingly, Lefty1 was directly regulated by HNF4α-1D, and Lefty1 knockdown also prevented the definitive endoderm differentiation. These results suggest that HNF4α-1D promotes definitive endoderm differentiation through the regulation of Lefty1. To our knowledge, this is the first report to clarify the expression pattern and function of HNF4α during the definitive endoderm differentiation.