Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.
Bioessays. 2013 Oct;35(10):853-61. doi: 10.1002/bies.201300059. Epub 2013 Jul 19.
The mammalian placenta exhibits elevated expression of endogenous retroviruses (ERVs), but the evolutionary significance of this feature remains unclear. I propose that ERV-mediated regulatory evolution was, and continues to be, an important mechanism underlying the evolution of placental development. Many recent studies have focused on the co-option of ERV-derived genes for specific functional adaptations in the placenta. However, the co-option of ERV-derived regulatory elements could potentially lead to the incorporation of entire gene regulatory networks, which, I argue, would facilitate relatively rapid developmental evolution of the placenta. I suggest a model in which an ancient retroviral infection led to the establishment of the ancestral placental developmental gene network through the co-option of ERV-derived regulatory elements. Consequently, placental development would require elevated tolerance to ERV activity. This in turn would expose a continuous stream of novel ERV mutations that may have catalyzed the developmental diversification of the mammalian placenta.
哺乳动物胎盘表现出内源性逆转录病毒 (ERVs) 的高表达，但这一特征的进化意义尚不清楚。我提出，ERV 介导的调控进化过去是，并且仍然是胎盘发育进化的重要机制。许多最近的研究都集中在 ERV 衍生基因的功能特化上，这些基因在胎盘中有特定的功能。然而，ERV 衍生调控元件的共选可能会导致整个基因调控网络的整合，我认为，这将促进胎盘的相对快速的进化。我提出一个模型，即一个古老的逆转录病毒感染通过共选 ERV 衍生的调控元件，导致了祖先胎盘发育基因网络的建立。因此，胎盘发育需要对 ERV 活性有更高的耐受性。这反过来又会暴露出一连串新的 ERV 突变，这些突变可能催化了哺乳动物胎盘的发育多样化。
