Palis James, Malik Jeffrey, McGrath Kathleen E, Kingsley Paul D
University of Rochester Medical Center, Department of Pediatrics, Center for Pediatric Biomedical Research, New York 14642, USA.
Int J Dev Biol. 2010;54(6-7):1011-8. doi: 10.1387/ijdb.093056jp.
Erythropoiesis in adult mammals is characterized by the progressive maturation of hematopoietic stem cells to lineage-specific progenitors, to morphologically identifiable precursors which enucleate to form mature erythrocytes. In contrast, primitive erythropoiesis is characterized by the appearance within the yolk sac of a transient, lineage-restricted progenitor population which generates a wave of erythroid precursors. These precursors undergo progressive maturation in the bloodstream, characterized by nuclear condensation and embryonic hemoglobin accumulation. This process is dependent on erythropoietin signaling through its cognate receptor, as well as the function of several erythroid-specific transcription factors, including GATA1 and EKLF. Targeted disruption of genes in the mouse that result in failure of the emergence or maturation of the primitive erythroid lineage leads to early fetal death, indicating that the primitive erythroid lineage is necessary for survival of the mammalian embryo. While it was thought for over a century that primitive erythroid cells were uniquely nucleated mammalian red cells, it is now recognized that they, like their definitive erythroid counterparts, enucleate to form reticulocytes and pyrenocytes. This surprising finding indicates that the primitive erythroid lineage is indeed mammalian, rather than non-mammalian, in character.
成年哺乳动物的红细胞生成的特征是造血干细胞逐步成熟为谱系特异性祖细胞，再成熟为形态上可识别的前体细胞，这些前体细胞通过去核形成成熟红细胞。相比之下，原始红细胞生成的特征是在卵黄囊中出现一群短暂的、谱系受限的祖细胞群体，该群体产生一波红细胞前体。这些前体在血液中经历逐步成熟，其特征是核浓缩和胚胎血红蛋白积累。这个过程依赖于促红细胞生成素通过其同源受体发出的信号，以及几种红细胞特异性转录因子的功能，包括GATA1和EKLF。在小鼠中对导致原始红细胞谱系出现或成熟失败的基因进行靶向破坏会导致早期胎儿死亡，这表明原始红细胞谱系对于哺乳动物胚胎的存活是必需的。虽然一个多世纪以来人们一直认为原始红细胞是唯一有核的哺乳动物红细胞，但现在人们认识到，它们与成熟红细胞一样，通过去核形成网织红细胞和核残体。这一惊人发现表明，原始红细胞谱系在本质上确实是哺乳动物的，而不是非哺乳动物的。
