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

Hepatocyte nuclear factor 4 alpha (HNF4 alpha) is a key transcription factor for liver development. Although HNF4 alpha is necessary for hepatoblast differentiation, the function of HNF4 alpha before the hepatoblast differentiation, such as in definitive endoderm differentiation, is not well known. In addition, it is known that there are nine HNF4 alpha isoforms, but the expression and function of each HNF4 alpha isoform during the definitive endoderm differentiation is also not clear. In this study, we examined the expression pattern of HNF4 alpha and its functions in the definitive endoderm differentiation from human induced pluripotent stem (iPS) cells. We found that the HNF4 alpha-1D isoform expression levels were significantly increased during the definitive endoderm differentiation, while the HNF4 alpha-1A isoform expression levels did not change. Therefore, we further examined the function of the HNF4 alpha-1D isoform in definitive endoderm differentiation. HNF4 alpha-1D overexpression or knockdown was found to promote or prevent the definitive endoderm differentiation, respectively. Interestingly, Lefty1 was directly regulated by HNF4 alpha-1D, and Lefty1 knockdown also prevented the definitive endoderm differentiation. These results suggest that HNF4 alpha-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 HNF4 alpha during the definitive endoderm differentiation.