Irie Naoko, Tang Walfred W C, Azim Surani M
Wellcome Trust/Cancer Research UK, Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QN UK.
Reprod Med Biol. 2014;13(4):203-215. doi: 10.1007/s12522-014-0184-2. Epub 2014 Jun 10.
Germ cells are unique cell types that generate a totipotent zygote upon fertilization, giving rise to the next generation in mammals and many other multicellular organisms. How germ cells acquire this ability has been of considerable interest. In mammals, primordial germ cells (PGCs), the precursors of sperm and oocytes, are specified around the time of gastrulation. PGCs are induced by signals from the surrounding extra-embryonic tissues to the equipotent epiblast cells that give rise to all cell types. Currently, the mechanism of PGC specification in mammals is best understood from studies in mice. Following implantation, the epiblast cells develop as an egg cylinder while the extra-embryonic ectoderm cells which are the source of important signals for PGC specification are located over the egg cylinder. However, in most cases, including humans, the epiblast cells develop as a planar disc, which alters the organization and the source of the signaling for cell fates. This, in turn, might have an effect on the precise mechanism of PGC specification in vivo as well as in vitro using pluripotent embryonic stem cells. Here, we discuss how the key early embryonic differences between rodents and other mammals may affect the establishment of the pluripotency network in vivo and in vitro, and consequently the basis for PGC specification, particularly from pluripotent embryonic stem cells in vitro.
生殖细胞是一类独特的细胞类型，受精时能产生全能合子，从而在哺乳动物和许多其他多细胞生物中孕育出下一代。生殖细胞如何获得这种能力一直备受关注。在哺乳动物中，原始生殖细胞（PGCs）是精子和卵子的前体，在原肠胚形成期左右被确定。PGCs由周围胚外组织发出的信号诱导产生，这些信号作用于能分化为所有细胞类型的全能上胚层细胞。目前，从对小鼠的研究中能最好地理解哺乳动物中PGCs确定的机制。着床后，上胚层细胞发育成卵圆柱状，而作为PGCs确定重要信号来源的胚外外胚层细胞位于卵圆柱上方。然而，在大多数情况下，包括人类，上胚层细胞发育成扁平盘状，这改变了细胞命运信号的组织和来源。反过来，这可能会影响体内以及使用多能胚胎干细胞在体外PGCs确定的精确机制。在此，我们讨论啮齿动物和其他哺乳动物早期胚胎的关键差异如何影响体内和体外多能性网络的建立，进而影响PGCs确定的基础，特别是体外多能胚胎干细胞的PGCs确定基础。
