Lee J T
Department of Molecular Biology, Massachusetts General Hospital, Boston 02114, USA.
Cell. 2000 Sep 29;103(1):17-27. doi: 10.1016/s0092-8674(00)00101-x.
In marsupials and in extraembryonic tissues of placental mammals, X inactivation is imprinted to occur on the paternal chromosome. Here, we find that imprinting is controlled by the antisense Xist gene, Tsix. Tsix is maternally expressed and mice carrying a Tsix deletion show normal paternal but impaired maternal transmission. Maternal inheritance occurs infrequently, with surviving progeny showing intrauterine growth retardation and reduced fertility. Transmission ratio distortion results from disrupted imprinting and postimplantation loss of mutant embryos. In contrast to effects in embryonic stem cells, deleting Tsix causes ectopic X inactivation in early male embryos and inactivation of both X chromosomes in female embryos, indicating that X chromosome counting cannot override Tsix imprinting. These results highlight differences between imprinted and random X inactivation but show that Tsix regulates both. We propose that an imprinting center lies within Tsix.
在有袋类动物以及胎盘哺乳动物的胚外组织中，X染色体失活被印记在父源染色体上。在此，我们发现这种印记是由反义Xist基因Tsix控制的。Tsix由母源表达，携带Tsix缺失的小鼠显示父源传递正常但母源传递受损。母源遗传很少发生，存活的后代表现出宫内生长迟缓以及生育力降低。传递率畸变是由印记破坏和突变胚胎植入后丢失导致的。与在胚胎干细胞中的效应相反，删除Tsix会导致早期雄性胚胎中出现异位X染色体失活，以及雌性胚胎中两条X染色体均失活，这表明X染色体计数无法超越Tsix印记。这些结果突出了印记X染色体失活和随机X染色体失活之间的差异，但表明Tsix对两者都有调节作用。我们提出一个印记中心位于Tsix内。
