Understanding how RIF1 and KAP1 enable the choice of the future active and inactive X chromosomes: the establishment of functional asymmetry.

了解 RIF1 和 KAP1 如何选择未来的活性和非活性 X 染色体：功能不对称的建立。

• 批准号: BB/W015544/1
• 负责人: Sara Buonomo
• 金额: $ 85.29万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FW015544%2F1
• 关键词: Understanding; how; RIF1; KAP1; enable

In humans, every chromosome is present in two copies, except in men, where there is one copy of each of the sex chromosomes, the X and the Y. Women have two copies of the X chromosome. One of the two X chromosomes in women is inactivated (silenced), so that male and female cells have the same amounts of the gene products coming from the X chromosomes. This process of silencing is called X-inactivation. Either of the two X chromosomes can be inactivated randomly. This means that, in every tissue, half of the cells would have one X chromosome inactive (A) and half would have the other one inactive (B). How is the random choice of one of the two X chromosome initially made? What are the mechanisms that inform one chromosome that other has been chosen? How is a different choice stably maintained in the progeny of each cell, throughout the life of an individual? These are all still unanswered or only partially-answered questions. In addition, in reality, the two copies of the X chromosome are never completely identical and the small differences in their DNA sequences can result in one of the two copies being silenced more easily. As a consequence, for example, if it is easier to silence X chromosome A, then most of the cells in a human organ will have an active B X chromosome, rather than a mixture of cells with an active A and cells with an active B. This is very important when one of the two X chromosomes contains a completely or partially defective gene which can cause a disease. If the X chromosome that is preferentially silenced carries the disease version of the gene, the organ will be functional and the woman will be healthy. But if, instead, the X chromosome, which is preferentially silenced, is the one carrying the normal version of the gene, the organ will not be able to function properly and the woman will suffer from the disease. Identifying the features of the DNA sequences that drive this skew and understanding how X-inactivation works are therefore very important, as they will allow the early identification of the patients at risk of developing severe symptoms, among the women carriers of X-linked diseases. An example of such a disease, where skewed X-inactivation plays a role in the severity of the symptoms, is Duchenne muscular dystrophy, where some female patients are completely asymptomatic and others are severely ill.In our project, we use mouse embryonic stem cells to investigate three molecules, an RNA and two proteins, that we have shown to be essential for the initial choice of which X chromosome will be inactivated. By studying how these three molecules interact with each other and with the X chromosome DNA, we will identify the molecular mechanism that establishes the choice of the identity of the future active and inactive X chromosomes. In addition, we will explore the role of DNA sequences that can determine skewed X chromosome silencing and investigate how these sequences relate to the unbalanced X chromosome inactivation observed in patients.

在人类中，每个染色体都有两个副本，除了男人，其中每个性别染色体，X和Y。女人都有两个X染色体的副本。女性中的两个X染色体之一被灭活（沉默），因此雄性和雌性细胞具有来自X染色体的相同量的基因产物。这种沉默的过程称为X灭活。两个X染色体中的任何一个都可以随机灭活。这意味着，在每个组织中，一半的细胞将具有一个X染色体无活性（A），而一半的细胞将具有另一个无活性（B）。两种X染色体之一的随机选择最初是如何进行的？哪些机制告知另一种染色体？在一个人的整个生命中，如何在每个细胞的后代中稳定地保持不同的选择？这些都是未解决的，或者只是部分提出的问题。此外，实际上，X染色体的两个副本永远不会完全相同，其DNA序列的小差异可能会导致两个副本之一更容易被沉默。因此，例如，如果更容易沉默X染色体A，那么人体器官中的大多数细胞将具有活性B X染色体，而不是与活性A的细胞混合物和具有活性B的细胞的混合物。当两个X染色体中的一个包含可能引起疾病的完全或部分有缺陷的基因时，这一点非常重要。如果优先沉默的X染色体带有该基因的疾病版本，则器官将是功能性的，女性将保持健康。但是，如果优先沉默的X染色体是携带基因正常版本的X染色体，则器官将无法正常运行，并且女性将患有该疾病。因此，在X连锁疾病的女性携带者中，确定驱动这一偏斜并了解X灭活的DNA序列的特征非常重要。 duchenne肌肉营养不良症是这种疾病的一个例子，其中偏斜的X灭活在症状的严重程度中起作用，其中一些女性患者完全无症状，而另一些女性则严重病了。在我们的项目中，我们使用小鼠胚胎干细胞为了研究三个分子，即RNA和两种蛋白，我们已证明对X染色体的初始选择至关重要。通过研究这三个分子如何相互相互作用以及与X染色体DNA相互作用，我们将确定建立未来活性和不活跃X染色体身份的选择的分子机制。此外，我们将探讨可以确定偏斜的X染色体沉默的DNA序列的作用，并研究这些序列与患者中观察到的不平衡X染色体失活的不平衡。