In liver development, hepatoblasts that act as hepatic stem/progenitor cells proliferate and differentiate into both hepatocytes and cholangiocytes to form liver tissues. Although numerous factors contribute to this event, little is known about the roles of microRNAs in hepatoblast proliferation and differentiation. In this study, we focused on the lineage-28 (Lin28) family proteins, which are required for microRNA regulation in pluripotent stem cells and cancer cells, and investigated their roles as regulatory factors for the properties of hepatoblasts. Conclusion: Lin28b was specifically expressed in hepatoblasts, and its suppression induced growth arrest and cholangiocyte differentiation of hepatoblasts; mechanistically, Lin28b positively regulates the expression of Lin28b itself and cell cycle–related proteins in hepatoblasts by suppressing the maturation of target microRNAs, lethal-7b and miR-125a/b, enabling maintenance of the stem cell properties of hepatoblasts, such as their capabilities for proliferation and bi-lineage differentiation, during liver development. (Hepatology 2016;64:245–260).
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