Roberts R M, Ealy A D, Alexenko A P, Han C S, Ezashi T
Department of Animal Sciences, University of Missouri, Columbia 65211-5300, USA.
Placenta. 1999 May;20(4):259-64. doi: 10.1053/plac.1998.0381.
The mechanisms responsible for prevention of corpus luteum regression during early pregnancy are diverse and appear to have arisen in concert with the evolutionary divergence of placental structure. That used by the sub-order Ruminantia is unique and involves the production of a Type I interferon (IFN), IFN-tau (tau). Although IFN-tau resembles other Type I IFNs (such as IFN-alpha, -beta, and -omega) in structure as well as in many of its biological properties, it is not virally inducible and is instead produced constitutively by embryonic trophectoderm during the period immediately prior to implantation. The transcription factor Ets-2 is a component of the regulatory mechanism involved in transcription of IFN-tau. These genes probably arose as the result of a duplication of an IFN-omega gene, 36 million years ago, at about the time the Ruminantia sub-order emerged. They have duplicated extensively since then and there may be 10 or more genes in some present-day species. The expression of different IFN-tau is unequal and they differ in biological potency. The rapid evolution of IFN-tau genes possibly reflects the placenta as a site of considerable genetic experimentation.
妊娠早期防止黄体退化的机制多种多样，而且似乎是与胎盘结构的进化分歧协同出现的。反刍亚目动物所采用的机制独一无二，涉及一种I型干扰素（IFN），即τ干扰素（IFN-τ）的产生。尽管IFN-τ在结构以及许多生物学特性上与其他I型干扰素（如IFN-α、-β和-ω）相似，但它不是病毒诱导产生的，而是在植入前的这段时间由胚胎滋养外胚层组成型产生。转录因子Ets-2是参与IFN-τ转录的调控机制的一个组成部分。这些基因可能是3600万年前一个IFN-ω基因复制的结果，大约在反刍亚目出现的时候。从那时起它们就大量复制，在一些现代物种中可能有10个或更多的基因。不同IFN-τ的表达是不平等的，它们的生物学效力也不同。IFN-τ基因的快速进化可能反映出胎盘是一个进行大量基因实验的场所。
