The Mammalian Yolk Sac Placenta
The Mammalian Yolk Sac Placenta
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DOI：
10.1002/jez.b.21239
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发表时间：
2009-09-15
影响因子：
2.2
通讯作者：
Renfree, Marilyn B.
中科院分区：
文献类型：
--
作者：
Freyer, Claudia;Renfree, Marilyn B.
哺乳动物有三种胎膜，即卵黄囊、尿囊和羊膜，但只有前两种形成胎盘。在单孔动物（Monotremata）、有袋动物（Marsupialia）和胎盘动物（Placentalia）中，卵黄囊转移来自子宫腺分泌物或母体血液的营养物质。在个体发育上，大多数真兽目动物的卵黄囊与外周绒毛膜失去接触，形成一个游离的内脏胸膜卵黄囊，从外体腔转移物质，而不是像有袋动物和啮齿动物那样直接从子宫内膜转移物质。这种游离的卵黄囊在人类中被保存下来，来自腺分泌物的物质通过这一途径从外体腔转移到胚胎中。哺乳动物卵黄囊表达许多生长和转录因子，相关的结合蛋白和受体，控制其分化和功能，包括造血和血管生成。卵黄囊发育和功能的缺陷可能导致胚胎畸形、流产和生长疾病。调节转移和代谢的因子，特别是胰岛素和IGF 2，被印在人类卵黄囊中，就像迄今为止研究的所有兽亚目动物一样。这表明，通过这种胎膜，父母控制的资源分配给生长中的胚胎的强烈选择压力持续存在。人类卵黄囊保留了真兽目祖先胚胎干细胞卵黄囊的代谢和生物合成功能，以及真兽目祖先的造血功能。因此，人类的卵黄囊，像所有胎生哺乳动物一样，是一个真正的胎盘，对早期胚胎发育和生存至关重要。J. Exp. Zool.（Mol. Dev. Evol.）312 B：545-554，2009. (C)2008 Wiley-Liss，Inc.
There are three fetal membranes in mammals, namely the yolk sac, allantois and amnion, but only the first two form a placenta. In Monotremata (monotremes), Marsupialia (marsupials) and Placentalia (eutherians), the yolk sac transfers nutrients originating from uterine glandular secretion or the maternal blood. Ontogenetically, the yolk sac of most eutherians loses contact with the peripheral chorion and forms a free splanchnopleuric yolk sac that transfers substances from the exocoelomic cavity, not directly from the endometrium as in marsupials and rodents. This free yolk sac has been preserved in humans and substances originating from glandular secretions are transferred from the exocoelomic cavity to the embryo via this route. The therian yolk sac expresses numerous growth and transcription factors, associated binding proteins and receptors that control its differentiation and function, including hematopoiesis and angiogenesis. Errors in yolk sac development and function could contribute to embryonic malformation, miscarriage and growth diseases. Factors regulating transfer and metabolism, notably insulin and IGF2, are imprinted in the human yolk sac, as in all therians so far studied. This suggests persistence of a strong selective pressure for parentally controlled allocation of resources to the growing embryo via this fetal membrane. The metabolic and biosynthetic functions of the yolk sac of the ancestral therian stem species, as well as hematopoiesis in the eutherian ancestor, appear to have been retained by the human yolk sac. Thus, the yolk sac of humans, like that of all viviparous mammals, is a true placenta crucial for early embryonic development and survival. J. Exp. Zool. (Mol. Dev. Evol.) 312B:545-554, 2009. (C) 2008 Wiley-Liss, Inc.