Regulation of X-chromosome inactivation and imprinting by non-coding elements

项目总结 长的非编码RNA和表观遗传复合体之间的相互作用现在被越来越多地认识到 发展决策的重要监管者。一个经典的例子是X染色体失活(XCI)，一种 在早期胚胎中一条X染色体失活的表观遗传过程。XCI可以 随机或以印记的方式放置在父亲的X上。在小鼠中，随机的XCI在 胚胎本身(胞体)，胎盘印记XCI。两者都需要X-失活中心(XIC)，以及 含有几个重要的非编码基因的X连锁区域。一个关键基因是Xist，它产生一种 一种非编码的RNA，它“绘制”X染色体，并在顺式染色体中招募沉默因子。我们的工作表明 在随机XCI过程中，Xist受到XIC因素的正向和负向调节，JPX在 正向通路和负向通路中的tSix/Xite。我们还证明了同源X- 染色体配对坐标哪个X染色体将被灭活。在这个资金周期中，我们有 进一步加深对XIC在X染色体计数、等位基因选择和印记中的作用的理解。 对于计数机制，JPX RNA--一种Xist激活剂--通过滴定充当X-连接的分子 常染色体“分母”，CTCF.这种滴定考虑了X与常染色体(X：A)的比率，并创建了 XIST诱导的允许状态。我们还了解到，X-X配对需要一个新的长的非编码RNA 被称为“Par-Terra”，产生于X连锁的伪常染色体区域(PAR)。有趣的是，所有的配对 相互作用发生在由两个XIC和两个PAR组成的“四分体”内。然后，X-X配对由mRNA来解析 去包裹酶，DCP1a。对于印记的XCI，我们已经建立了一个体外细胞模型来研究XP 印记。我们已经证明了200kb的XIC区域足以指导Xist印记，并且Xist 印记要求雄性生殖系处于类似于减数分裂性染色体的未配对状态。 失活(MSCI)。我们的研究创造了新的机会和许多额外的机制 问题。在下一个资金周期中，我们的目标是(I)研究X-X配对和 X染色体对称性的破坏，(Ii)确定JPX-CTCF滴定如何调节XCI的启动， (3)阐明印迹XCI的作用机制。拟议的工作将需要五年时间才能完成 预计将为表观遗传学和RNA领域的学术生涯培训三名博士后研究员 生物学。

PROJECT SUMMARY Interactions between long noncoding RNAs and epigenetic complexes are now increasingly recognized as important regulators of developmental decisions. A classic example is X-chromosome inactivation (XCI), an epigenetic process by which one X-chromosome becomes inactivated in the early embryo. XCI can take place randomly or in an imprinted manner on the paternal X. In the mouse, random XCI is observed in the embryo proper (soma), and imprinted XCI in the placenta. Both require the ‘X-inactivation center’ (Xic), an X-linked region that harbors several essential noncoding genes. A key gene is Xist, which produces a noncoding RNA that ‘paints’ the X-chromosome and recruits silencing factors in cis. Our work has shown that, during random XCI, Xist is regulated both positively and negatively by Xic factors, with Jpx in the positive pathway and Tsix/Xite in the negative pathway. We have also shown that homologous X- chromosome pairing coordinates which X chromosome will be inactivated. In this funding cycle, we have further advanced understanding of the Xic’s role in X-chromosome counting, allelic choice, and imprinting. For the counting mechanism, Jpx RNA — an Xist activator — serves as an X-linked “numerator” by titrating the autosomal “denominator”, CTCF. This titration accounts for the X-to-autosome (X:A) ratio and creates a permissive state for Xist induction. We also learned that X-X pairing requires a new long noncoding RNA called “PAR-TERRA” produced from the X-linked pseudoautosomal region (PAR). Interestingly, all pairing interactions take place within a “tetrad” of two Xic’s and two PAR’s. X-X pairing is then resolved by mRNA decapping enzyme, DCP1A. For imprinted XCI, we have generated an ex vivo cellular model to study XP imprinting. We have demonstrated that a 200-kb Xic region is sufficient to direct Xist imprinting and that Xist imprinting requires an unpaired state in the male germ line that is akin to meiotic sex chromosome inactivation (MSCI). Our research has generated new opportunities and many additional mechanistic questions. In the next funding cycle, we aim to (i) investigate mechanisms underlying X-X pairing and breaking of X-chromosome symmetry, (ii) determine how Jpx-CTCF titration regulates the initiation of XCI, and (iii) elucidate the mechanisms of imprinted XCI. The proposed work will require five years to complete and is expected to train three postdoctoral fellows for academic careers in the fields of epigenetics and RNA biology.