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Human germline in vitro models for development and the epigenetic program

人类种系体外发育模型和表观遗传程序

基本信息

批准号：
MR/P009948/1
负责人：
Azim Surani
金额：
$ 81.21万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=MR%2FP009948%2F1
关键词：
Human germline vitro models development

项目摘要

Germ cells, the precursors of sperm and egg, are unique and considered to be immortal in the sense that they generate a new organism, and theoretically at least, give rise to endless generations. By contrast, somatic (body) cells perish with each generation. Germ cells transmit genetic instructions that are passed on from one generation to the next. The germline also transmits non-genetic (epigenetic) information, which can regulate gene expression in developing embryos and adults, but without alterations to the genetic information. Epigenetic modifications can be induced and erased but some can persist intergenerationally, and potentially, transgenerationally. The parent-of-origin specific genomic imprints that have an essential role in human development persist intergenerationally. Faulty imprints result in a number of diseases that affect behavior, growth and obesity. Environmental factors, including diet can also apparently induce epigenetic modifications in germ cells according to some studies, which could be transmitted transgenerationally with potential consequences for human health. To gain insight into mechanisms of induction and transmission of epigenetic information, it is essential to understand the underlying mechanisms of how the information might accrue, and evade the robust germline reprogramming to be transmitted through the germline. Studies on human germ cells are challenging. Since many dynamic events for germ cell development occur in early developmental stages in the uterus, where human germ cells are not readily accessible or testable experimentally, except for the rare germ cells that can be obtained from aborted fetuses. Moreover, the extensively used mouse model for germ cell development does not accurately reflect mechanisms of human germline development, since critical differences have become evident recently. For this reason, it is essential to develop tractable experimental models in culture that can be manipulated and tested in culture.Aberrant germ cells and mutations can also be the cause of infertility and germ cell tumors. Purification of mitochondria also occurs in early germ cells before their transmission through eggs. An increase in the proportion of defective mitochondria causes many human diseases. Research on germ cells is required to understand the underlying mechanisms, for the development of diagnostic methods, and potential treatment of germline associated diseases. A robust and quantitative culture model for human germline development using induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), including some derived from affected patients would represent a major advance. Patient derived iPSCs provide a powerful tool if they carry mutations affecting genomic and epigenomic information that might be the cause of specific germline disorders. Recently, we established a robust culture system for early PGCs differentiation using human iPSCs and ESCs (Irie et al., 2015); this provided information on the key regulators of the human germline for the first time. This also showed that extrapolation from studies in mice to humans may not provide valid information for the latter. However, under the current culture system, PGCs develop up to the early stages of initiation of the epigenetic program but not its completion. With the additional information we now have on later stages of germ cells isolated from aborted fetuses, we can exploit this knowledge to develop efficient culture model for more advanced PGC development.The latest efficient genome editing (CRISPR/Cas9) technique combined with the patient specific iPSCs will allow us to confirm the precise genomic evidence for the diseases. These studies may also be informative for the causes of germ cell tumors such as seminomas, embryonal carcinomas, and the pediatric brain tumors called germinomas that originate from early germ cells.

生殖细胞是精子和卵子的前体，是独特的，并且被认为是不朽的，因为它们产生了新的有机体，并且至少在理论上，可以产生无穷无尽的后代。相比之下，体细胞随着每一代的发生而死亡。生殖细胞传递遗传指令，并代代相传。种系还传递非遗传（表观遗传）信息，可以调节发育中的胚胎和成人的基因表达，但不会改变遗传信息。表观遗传修饰可以被诱导和消除，但有些可以在代际间持续存在，甚至可能跨代持续存在。在人类发育中具有重要作用的亲本特异性基因组印记在代际间持续存在。错误的印记会导致许多影响行为、生长和肥胖的疾病。根据一些研究，包括饮食在内的环境因素显然也可以诱导生殖细胞的表观遗传修饰，这种修饰可能会跨代传播，对人类健康产生潜在影响。为了深入了解表观遗传信息的诱导和传递机制，有必要了解信息如何产生的潜在机制，并逃避通过种系传递的强大种系重编程。对人类生殖细胞的研究具有挑战性。由于生殖细胞发育的许多动态事件发生在子宫的早期发育阶段，除了可以从流产胎儿获得的稀有生殖细胞外，人类生殖细胞不易通过实验获得或测试。此外，广泛使用的生殖细胞发育小鼠模型并不能准确反映人类生殖细胞发育的机制，因为最近已经变得明显的关键差异。因此，有必要开发易于处理的培养实验模型，以便在培养中进行操作和测试。异常的生殖细胞和突变也可能是不孕症和生殖细胞肿瘤的原因。在早期生殖细胞通过卵子传播之前，线粒体的纯化也发生在早期生殖细胞中。有缺陷的线粒体比例的增加会导致许多人类疾病。需要对生殖细胞进行研究，以了解其潜在机制，以开发诊断方法以及生殖系相关疾病的潜在治疗方法。使用诱导多能干细胞（iPSC）和胚胎干细胞（ESC）（包括一些来自受影响患者的细胞）建立用于人类生殖系发育的稳健且定量的培养模型将代表着一项重大进展。如果患者来源的 iPSC 携带影响基因组和表观基因组信息的突变，而这些信息可能是特定种系疾病的原因，那么它们就提供了一个强大的工具。最近，我们利用人类 iPSC 和 ESC 建立了一个强大的用于早期 PGC 分化的培养系统（Irie 等，2015）；这首次提供了有关人类种系关键调节因子的信息。这也表明，从小鼠研究推断到人类可能无法为后者提供有效信息。然而，在当前的培养体系下，PGC 发育到表观遗传程序启动的早期阶段，但尚未完成。有了我们现在从流产胎儿中分离出的生殖细胞后期阶段的更多信息，我们可以利用这些知识来开发高效的培养模型，以实现更先进的 PGC 开发。最新的高效基因组编辑 (CRISPR/Cas9) 技术与患者特异性 iPSC 相结合，将使我们能够确认疾病的精确基因组证据。这些研究也可能为生殖细胞肿瘤的病因提供信息，例如精原细胞瘤、胚胎癌和源自早期生殖细胞的被称为生殖细胞瘤的小儿脑肿瘤。