Single-cell murine genetic fate mapping reveals bipotential hepatoblasts and novel multi-organ endoderm progenitors

Abstract

The definitive endoderm (DE) is the embryonic germ layer that forms the gut tube and associated organs including thymus, lungs, liver and pancreas. To understand how individual DE cells furnish gut organs, genetic fate mapping was performed using the Rosa26LacZ Cre-reporter paired with a tamoxifen inducible DE-specific Cre-expressing transgene. We established a low tamoxifen dose that infrequently induced heritable LacZ-expression in a single cell of individual E8.5 embryos to identify clonal cell descendants at E16.5. As expected, only a fraction of the E16.5 embryos contained LacZ-positive clonal descendants and a subset of these contained descendants in multiple organs, revealing novel ontogeny. Furthermore, immunohistochemical analysis was used to identify LacZ-positive hepatocytes and biliary epithelial cells, the cholangiocyte precursor, in each clonally populated liver. Together these data not only uncover novel and suspected lineage relationships between DE-derived organs but also illustrate the bipotential nature of individual hepatoblasts, by demonstrating that single hepatoblasts contribute to both the hepatocyte and the cholangiocyte lineage in vivo.