Kay G F, Penny G D, Patel D, Ashworth A, Brockdorff N, Rastan S
Section of Comparative Biology, Medical Research Council Clinical Research Centre, Harrow, England.
Cell. 1993 Jan 29;72(2):171-82. doi: 10.1016/0092-8674(93)90658-d.
The mouse Xist gene maps to the X inactivation center (Xic) region and is expressed exclusively from the inactive X chromosome. It is thus a candidate gene for the Xic. We show that the onset of Xist expression in mouse development precedes X chromosome inactivation and may therefore be a cause rather than merely a consequence of X inactivation. The earliest Xist expression in morulae and blastocysts is imprinted, resulting in specific expression of the paternal Xist allele. Imprinted Xist expression may thus be the cause of nonrandom inactivation of the paternal X in trophectoderm. Strong Xce alleles can act to reduce the effect of imprinted Xist expression in the trophectoderm. The imprint on Xist expression is lost shortly before gastrulation when random X inactivation occurs. Our data support a direct role for Xist in the initiation of X inactivation.
小鼠的Xist基因定位于X染色体失活中心（Xic）区域，且仅从不活跃的X染色体上表达。因此，它是Xic的一个候选基因。我们发现，小鼠发育过程中Xist表达的起始先于X染色体失活，所以它可能是X染色体失活的原因，而不仅仅是其结果。桑椹胚和囊胚中最早的Xist表达是印记的，导致父本Xist等位基因的特异性表达。因此，印记的Xist表达可能是滋养外胚层中父本X染色体非随机失活的原因。强Xce等位基因可起到减少滋养外胚层中印记Xist表达的作用。当发生随机X染色体失活时，Xist表达上的印记在原肠胚形成前不久消失。我们的数据支持Xist在X染色体失活起始过程中起直接作用。
