A number of placenta-specific genes (e.g., Tpbp, Plac1, Syncytin, and retrotransposon-associated genes such as Peg10, Rtl1, Endothelin B receptor, Insl4, Leptin, Midline1, and Pleiotrophin), enhancer elements (e.g., glycoprotein hormone alpha-subunit) and gene isoforms (e.g., 3betaHSD, Cyp19), as well as placenta-specific members of gene families (e.g., Gcm1, Mash2, Rhox, Esx1, Cathepsin, PAG, TKDP, Psg, Siglec) have been identified. This review summarizes their evolution, regulation, and biochemical functions and discusses their significance for placental development and function. Strikingly, the number of unique, truly placenta-specific genes that have been discovered to date is very small. The vast majority of placenta-specific gene products have resulted from one of three mechanisms: evolution of placenta-specific promoters, evolution of large gene families with several placenta-specific members, or adoption of functions associated with endogenous retroviruses and retroelements. Interestingly, nearly all the examples of placenta-specific genes that have been discovered to date are not present in all placental mammals.

中文翻译：

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胎盘特异性基因的进化，调控和功能。

许多胎盘特异性基因（例如，Tpbp，Plac1，Syncytin和逆转录转座子相关基因，例如Peg10，Rtl1，内皮素B受体，Insl4，瘦素，中线1和促卵磷脂），增强子元件（例如，糖蛋白激素α-亚型）和基因同工型（例如3betaHSD，Cyp19），以及基因家族的胎盘特异性成员（例如Gcm1，Mash2，Rhox，Esx1，Cathepsin，PAG，TKDP，Psg，Siglec）已被鉴定。这篇综述总结了它们的进化，调节和生化功能，并讨论了它们对胎盘发育和功能的重要性。令人惊讶的是，迄今为止发现的独特的，真正的胎盘特异性基因数量非常少。绝大多数胎盘特异性基因产物是由以下三种机制之一产生的：胎盘特异性启动子的进化，具有几个胎盘特异性成员的大基因家族的进化，或采用与内源性逆转录病毒和逆转录元件相关的功能。有趣的是，迄今发现的几乎所有胎盘特异性基因的例子都并非在所有胎盘哺乳动物中都存在。