Epigenetic Mechanisms of X-chromosome Inactivation

描述(由申请人提供)：X染色体失活(XCI)是表观遗传基因调控的一种范例。XCI导致雌性哺乳动物两条X染色体中的一条的基因转录沉默，并导致X连锁基因剂量与XY雄性相当。一旦在早期女性胚胎的单个细胞中发生XCI，XCI就会稳定地传播，从而使所有后代细胞保持该X染色体的沉默。由于整个染色体被灭活，因此很容易被检测到，XCI是一个模型系统，可以深入了解维持转录记忆的机制。重要的是，在XCI期间运行的记忆机制通常适用于其他地方的基因沉默，并被发现在人类疾病中出现错误。 由Polycomb group(PcG)编码的蛋白质调节基因的长期抑制，包括在XCI期间。PCG在XCI早期被发现富含在XI上，导致了它们有助于启动XCI的想法。在这项应用中，候选人将测试PCGS是否需要在胚胎发育的早期启动印记XCI。他最近通过免疫荧光检测到一种新的蛋白质在XI上浓缩；在这里，他建议鉴定这种蛋白质，表征其在表观遗传中的生化功能，并定义其在XCI期间的需求。 该奖项将大大促进候选人建立一个独立实验室的目标，该实验室的重点是遗传和生物化学定义因子及其在表观遗传基因调控中的功能。导师的实验室为在哺乳动物系统中进行表观遗传学研究提供了一个刺激的环境。在奖项的指导阶段，候选人将确定PCGS是否启动印迹XCI，并识别和表征一种富含在XI上的新蛋白质。这将包括在确定植入前阶段胚胎的XCI缺陷和蛋白质鉴定方面的改进技术。在奖项的独立阶段，候选人将描述新的富含XI的蛋白质的功能，并确定相互作用的成分。在这一阶段，他还将定义新基因在XCI特定阶段的需求。 新出现的证据越来越多地表明，表观遗传机制的错误调控是人类疾病的一个原因或一个重要因素。识别和描绘新的表观遗传因子及其功能将提供对人类疾病(包括各种癌症)中被绕过或被增选的机制的洞察。

DESCRIPTION (provided by applicant): X-chromosome inactivation (XCI) is a paradigm of epigenetic gene regulation. XCI results in transcriptional silencing of genes along one of the two X-chromosomes in female mammals and leads to equivalence of X-linked gene dosage with that of XY males. Once enacted in individual cells of the early female embryo, XCI is stably transmitted such that all descendant cells maintain silencing of that X chromosome. Since an entire chromosome is inactivated and therefore easily detected, XCI is a model system to gain insights into the machinery that maintains transcriptional memory. Importantly, the memory mechanisms that operate during XCI often apply to gene silencing elsewhere and are being found to go awry in human disorders. Proteins encoded by the Polycomb group (PcG) mediate long-term repression of genes, including during XCI. PcGs are found enriched on the Xi early during XCI, leading to the idea that they help initiate XCI. In this application, the candidate will test if PcGs are required to initiate imprinted XCI during early embryogenesis. He has recently detected the enrichment of a novel protein on the Xi by immunofluorescence; here he proposes to identify the protein, characterize its biochemical function in epignenetic inheritance, and define its requirement during XCI. The award will considerably facilitate the candidate's goal of establishing an independent laboratory with the focus of genetically and biochemically defining factors and their function in epigenetic gene regulation. The mentor's laboratory provides a stimulating environment for conducting epigenetic research in the mammalian system. During the mentored phase of the award, the candidate will determine if PcGs initiate imprinted XCI and also identify as well as characterize a novel protein that is enriched on the Xi. This will involve refining techniques in defining XCI defects in pre-implantation stage embryos and in protein identification. In the independent phase of the award, the candidate will delineate a function to the novel Xi-enriched protein and identify interacting components. In this phase, he will also define the requirement of the novel gene in specific phases of XCI. Emerging evidence increasingly implicates the misregulation of the epigenetic machinery as a cause of or a significant contributor to human disease. The identification and delineation of novel epigenetic factors and their function will provide insight into the mechanisms that are either bypassed or co-opted in human disorders, including various cancers.