Dunlap Kathrin A, Palmarini Massimo, Varela Mariana, Burghardt Robert C, Hayashi Kanako, Farmer Jennifer L, Spencer Thomas E
Center for Animal Biotechnology and Genomics, Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.
Proc Natl Acad Sci U S A. 2006 Sep 26;103(39):14390-5. doi: 10.1073/pnas.0603836103. Epub 2006 Sep 15.
Endogenous retroviruses (ERVs) are fixed and abundant in the genomes of vertebrates. Circumstantial evidence suggests that ERVs play a role in mammalian reproduction, particularly placental morphogenesis, because intact ERV envelope genes were found to be expressed in the syncytiotrophoblasts of human and mouse placenta and to elicit fusion of cells in vitro. We report here in vivo and in vitro experiments finding that the envelope of a particular class of ERVs of sheep, endogenous Jaagsiekte sheep retroviruses (enJSRVs), regulates trophectoderm growth and differentiation in the periimplantation conceptus (embryo/fetus and associated extraembryonic membranes). The enJSRV envelope gene is expressed in the trophectoderm of the elongating ovine conceptus after day 12 of pregnancy. Loss-of-function experiments were conducted in utero by injecting morpholino antisense oligonucleotides on day 8 of pregnancy that blocked enJSRV envelope protein production in the conceptus trophectoderm. This approach retarded trophectoderm outgrowth during conceptus elongation and inhibited trophoblast giant binucleate cell differentiation as observed on day 16. Pregnancy loss was observed by day 20 in sheep receiving morpholino antisense oligonucleotides. In vitro inhibition of the enJSRV envelope reduced the proliferation of mononuclear trophectoderm cells isolated from day 15 conceptuses. Consequently, these results demonstrate that the enJSRV envelope regulates trophectoderm growth and differentiation in the periimplantation ovine conceptus. This work supports the hypothesis that ERVs play fundamental roles in placental morphogenesis and mammalian reproduction.
内源性逆转录病毒（ERVs）在脊椎动物基因组中固定且丰富。间接证据表明，ERVs在哺乳动物繁殖中发挥作用，特别是在胎盘形态发生过程中，因为发现完整的ERV包膜基因在人和小鼠胎盘的合体滋养层细胞中表达，并在体外引发细胞融合。我们在此报告体内和体外实验结果，发现绵羊的一类特定ERVs，即内源性绵羊肺腺瘤逆转录病毒（enJSRVs）的包膜，可调节着床前孕体（胚胎/胎儿及相关的胚外膜）中滋养外胚层的生长和分化。enJSRV包膜基因在怀孕12天后伸长的绵羊孕体的滋养外胚层中表达。在怀孕第8天通过子宫内注射吗啉代反义寡核苷酸进行功能丧失实验，该寡核苷酸可阻断孕体滋养外胚层中enJSRV包膜蛋白的产生。如在第16天观察到的，这种方法减缓了孕体伸长过程中滋养外胚层的生长，并抑制了滋养层巨型双核细胞的分化。在接受吗啉代反义寡核苷酸的绵羊中，到第20天时观察到妊娠丢失。体外抑制enJSRV包膜可降低从第15天孕体分离的单核滋养外胚层细胞的增殖。因此，这些结果表明，enJSRV包膜调节着床前绵羊孕体中滋养外胚层的生长和分化。这项工作支持了ERVs在胎盘形态发生和哺乳动物繁殖中发挥重要作用的假说。
