Department of Stem Cell and Developmental Biology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu 514-8507, Japan.
Int J Mol Sci. 2020 Dec 8;21(24):9346. doi: 10.3390/ijms21249346.
Primitive erythrocytes are the first hematopoietic cells observed during ontogeny and are produced specifically in the yolk sac. Primitive erythrocytes express distinct hemoglobins compared with adult erythrocytes and circulate in the blood in the nucleated form. Hematopoietic stem cells produce adult-type (so-called definitive) erythrocytes. However, hematopoietic stem cells do not appear until the late embryonic/early fetal stage. Recent studies have shown that diverse types of hematopoietic progenitors are present in the yolk sac as well as primitive erythroblasts. Multipotent hematopoietic progenitors that arose in the yolk sac before hematopoietic stem cells emerged likely fill the gap between primitive erythropoiesis and hematopoietic stem-cell-originated definitive erythropoiesis and hematopoiesis. In this review, we discuss the cellular origin of primitive erythropoiesis in the yolk sac and definitive hematopoiesis in the fetal liver. We also describe mechanisms for developmental switches that occur during embryonic and fetal erythropoiesis and hematopoiesis, particularly focusing on recent studies performed in mice.
原始红细胞是个体发生过程中最早观察到的造血细胞，专门在卵黄囊中产生。原始红细胞表达的血红蛋白与成体红细胞明显不同，并以有核形式在血液中循环。造血干细胞产生成体型（所谓的定型）红细胞。然而，造血干细胞直到胚胎晚期/胎儿早期才出现。最近的研究表明，卵黄囊以及原始红细胞中存在多种类型的造血祖细胞。在造血干细胞出现之前，可能在卵黄囊中出现的多能造血祖细胞填补了原始红细胞生成和造血干细胞起源的定型红细胞生成和造血之间的空白。在这篇综述中，我们讨论了卵黄囊原始红细胞生成和胎儿肝脏定型造血的细胞起源。我们还描述了胚胎和胎儿红细胞生成和造血过程中发生的发育开关的机制，特别是重点介绍了在小鼠中进行的最近的研究。
