Epigenetic control of the human X chromosome

人类 X 染色体的表观遗传控制

• 批准号: 9921448
• 负责人: Kathrin Plath
• 金额: $ 43.61万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-05-01 至 2024-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9921448
• 关键词: 3-Dimensional; Behavior; Biological Assay; Cell physiology; Cells; Chromatin; Data; Development; Disease; Dosage Compensation (Genetics); Embryo; Embryonic Development; Epigenetic Process; Evolution; Female; Gene Dosage; Gene Expression; Gene Expression Regulation; Gene Silencing; Genes; Genetic Transcription; Genome; Goals; Human; Human Development; Human X Chromosome; In Vitro; Link; Mammals; Measures; Mediating; Molecular; Mus; Play; Primates; Problem Solving; Process; Proteins; Publishing; Regulation; Regulator Genes; Role; Sex Chromosomes; Site; Untranslated RNA; Work; X Chromosome; X Inactivation; autosome; base; blastocyst; cell type; dosage; experimental study; human embryonic stem cell; implantation; imprint; innovation; male; novel; pluripotency; preimplantation

PROJECT SUMMARY The overall goal of this proposal is to study the regulation of X-chromosome dosage compensation by long- noncoding (lnc) RNAs in human embryonic stem cells (hESCs) to fundamentally advance the understanding of early human development, the regulation of pluripotency states, and mechanisms of gene regulation by lncRNAs. X-chromosome dosage compensation is an essential process that equalizes X-linked gene expression between females and males and is initiated early in development. In mammals, it is mediated by X-chromosome inactivation (XCI), the transcriptional silencing of genes on one of the two X-chromosomes in females. Mechanistic studies of XCI have been carried out in mice and established that the lncRNA Xist, encoded on the X chromosome, spreads along the X chromosome to mediate XCI. Although XCI occurs in both mouse and human post-implantation development, the regulation of X-chromosome dosage in pre-implantation embryos has evolved differently between the two species. In pre-implantation development, mouse embryos undergo an imprinted form of XCI, while human embryos lack imprinted XCI and instead regulate gene expression by dampening transcription on both X-chromosomes. X-chromosome dampening (XCD) is different from XCI as it occurs on both X chromosomes in contrast to the complete transcriptional silencing of one X. Additional remarkable differences between human and mouse include the unprecedented expression and accumulation of XIST on the active (dampened) X-chromosomes and the expression of the primate- and pluripotency-specific lncRNA XACT from the X in human pre-implantation embryos. Thus, X-linked gene dosage in humans is regulated first by XCD and upon implantation by XCI, and remarkably, XIST expression is uncoupled from silencing when XCD takes place. A mechanistic understanding of XCD, lack of silencing by XIST in pre- implantation embryos, XIST's transition to mediating XCI, and the role of the lncRNA XACT is lacking, and it is not known if XIST has any role in human pre-implantation cells or XCD. We discovered that naïve hESCs recapitulate in vitro many of the unique features of human X-chromosome dosage compensation, including XCD, expression of XIST on active X-chromosomes, XACT expression, and initiation of XCI upon differentiation. Here, we will take advantage of naïve hESCs to investigate how XIST expression does not induce silencing early in development and later acquires the ability to silence, to reveal regulatory mechanisms of human XCD and XCI, and if XACT controls XIST functions. We have the following Specific Aims: 1) We will define the function of XIST in naïve hESCs, its requirement for XCD, and mechanisms of XCD. 2) We will define chromatin targets and protein interactors of XIST to understand its differential silencing ability in naïve and primed hESCs. 3) We will characterize the function and localization of the lncRNA XACT. Understanding the mechanisms of human X- chromosome dosage compensation will allow us to advance our understanding of epigenetic features unique to human development and reveal how key epigenetic processes are changing in evolution.

项目概要 该提案的总体目标是研究长链对X染色体剂量补偿的调节 人类胚胎干细胞 (hESC) 中的非编码 (lnc) RNA 从根本上促进对 早期人类发育、多能状态的调节以及 lncRNA 的基因调节机制。 X染色体剂量补偿是均衡X连锁基因表达的重要过程 在哺乳动物中，它由 X 染色体介导，在雌性和雄性中均存在。 失活（XCI），女性两条 X 染色体之一上的基因转录沉默。 XCI 的机制研究已在小鼠中进行，并确定 lncRNA Xist 编码于 X 染色体，沿着 X 染色体传播以介导 XCI，尽管 XCI 发生在小鼠和小鼠中。 人类植入后发育，植入前胚胎中X染色体剂量的调节 在植入前发育过程中，两个物种之间的进化有所不同。 XCI 的印迹形式，而人类胚胎缺乏印迹 XCI，而是通过 X 染色体抑制 (XCD) 与 XCI 不同。 与一条 X 染色体的完全转录沉默相反，该现象发生在两条 X 染色体上。 人类和小鼠之间的显着差异包括前所未有的表达和积累 活性（减弱）X 染色体上的 XIST 以及灵长类和多能性特异性的表达 lncRNA XACT 来自人类植入前胚胎中的 X 因此，人类中的 X 连锁基因剂量是。 首先由 XCD 调节，并在植入后由 XCI 调节，并且不常见的是，XIST 表达与 XCD 发生时的沉默 对 XCD 的机制理解，XIST 缺乏沉默。 着床胚胎，XIST向介导XCI的转变，缺乏lncRNA XACT的作用， 尚不清楚 XIST 在人类植入前细胞或 XCD 中是否有任何作用，我们发现了幼稚 hESC。 在体外重现人类 X 染色体剂量补偿的许多独特特征，包括 XCD、 XIST 在活性 X 染色体上的表达、XACT 表达以及分化时 XCI 的启动。 我们将利用幼稚 hESC 来研究 XIST 表达如何在早期不诱导沉默。 发展，后来获得沉默的能力，揭示人类 XCD 和 XCI 的调节机制， 如果 XACT 控制 XIST 功能，我们有以下具体目标： 1）我们将定义 XIST 的功能。 在幼稚 hESC 中，其对 XCD 的要求以及 XCD 的机制 2) 我们将定义染色质靶点和机制。 XIST 的蛋白质相互作用子，以了解其在幼稚和引发的 hESC 中的差异沉默能力 3) 我们将。 表征 lncRNA XACT 的功能和定位 了解人类 X- 的机制。 染色体剂量补偿将使我们能够加深对染色体独特的表观遗传特征的理解 人类发展并揭示关键的表观遗传过程在进化中如何变化。