During embryogenesis, the liver is the site of hepatogenesis and hematopoiesis and contains many cell lineages derived from the endoderm and mesoderm. However, the characteristics and developmental programs of many of these cell lineages remain unclear, especially in humans. Here, we performed single-cell RNA sequencing of whole human and mouse fetal livers throughout development. We identified four cell lineage families of endoderm-derived, erythroid, non-erythroid hematopoietic, and mesoderm-derived non-hematopoietic cells, and defined the developmental pathways of the major cell lineage families. In both humans and mice, we identified novel markers of hepatic lineages and an ID3⁺ subpopulation of hepatoblasts as well as verified that hepatoblast differentiation follows the “default-directed” model. Additionally, we found that human but not mouse fetal hepatocytes display heterogeneity associated with expression of metabolism-related genes. We described the developmental process of erythroid progenitor cells during human and mouse hematopoiesis. Moreover, despite the general conservation of cell differentiation programs between species, we observed different cell lineage compositions during hematopoiesis in the human and mouse fetal livers. Taken together, these results reveal the dynamic cell landscape of fetal liver development and illustrate the similarities and differences in liver development between species, providing an extensive resource for inducing various liver cell lineages in vitro.

在胚胎发生过程中，肝脏是肝发生和造血的场所，包含许多来自内胚层和中胚层的细胞谱系。然而，许多这些细胞谱系的特征和发育程序仍不清楚，尤其是在人类中。在这里，我们在整个发育过程中对整个人和小鼠胎儿肝脏进行了单细胞 RNA 测序。我们确定了内胚层衍生的、红系、非红系造血细胞和中胚层衍生的非造血细胞的四个细胞谱系家族，并确定了主要细胞谱系家族的发育途径。在人类和小鼠中，我们确定了肝脏谱系的新标记和 ID3 ⁺成肝细胞亚群以及证实肝细胞分化遵循“默认导向”模型。此外，我们发现人类而非小鼠胎儿肝细胞表现出与代谢相关基因表达相关的异质性。我们描述了人类和小鼠造血过程中红系祖细胞的发育过程。此外，尽管物种之间的细胞分化程序普遍保守，但我们在人和小鼠胎肝的造血过程中观察到了不同的细胞谱系组成。综上所述，这些结果揭示了胎肝发育的动态细胞图谱，并说明了物种之间肝脏发育的异同，为体外诱导各种肝细胞谱系提供了广泛的资源。