Genomic reprogramming in the early embryo

项目摘要 我们的长期目标是阐明重组基因组的分子机制， 从特定细胞类型到多能状态的转变。在胚胎发育的最初阶段， 特定生殖细胞的基因组被快速和有效地重编程以产生多能细胞， 早期胚胎在早期胚胎中发生的高效重编程和 以及在培养中发生的效率更低的重编程。产生多能干细胞的能力 在疾病建模和治疗方面具有巨大潜力。了解基本的分子 驱动重编程的机制将对我们快速和可重复地 诱导多能状态。无论是在培养物中还是在早期胚胎中，重编程都需要 专门的转录因子，称为先锋因子。先锋因素的独特之处在于， 转录因子，它们可以在核小体的背景下结合到DNA。这一特点使他们独特的 访问基因组，并有助于重新定义染色质可及性景观。尽管如此， 尚不清楚先驱因子的哪些特定功能需要驱动重编程，以及障碍是什么 开创因子介导的重编程。在果蝇中，转录因子塞尔达是启动 合子基因组的转录激活。我们已经证明了塞尔达拥有 的先驱转录因子，这种活动是需要在整个过程合子基因组 activation.然而，塞尔达不太可能独立工作，我们已经牵连到另一个开拓者， 因子，GAGA因子，作为功能与塞尔达一起定义可访问的染色质结构域在早期 胚胎通过结合我们开发的新工具来询问转录因子在早期的功能， 凭借经过充分研究的苍蝇系统的优势，我们处于独特的地位，可以确定基本的 重编程的特点。我们将使用遗传学、基因组学、生物化学和成像策略来1）确定如何 先锋因子合作重新编程合子基因组，2）识别先锋因子的染色质屏障- 介导的重编程和3）确定内在无序区域在建立染色质中的作用 在早期胚胎中。我们提出的研究是重要的，因为通过定义基本特征， 我们将确定有效重编程转录因子所需的统一原则。 特定细胞的多能性。

PROJECT SUMMARY Our long-term goal is to elucidate the molecular mechanisms that restructure the genome to allow for the transition from a specified cell type to a pluripotent state. During the initial stages of embryonic development, the genomes of the specified germ cells are rapidly and efficiently reprogrammed to generate the pluripotent cells of the early embryo. Many features are shared between the efficient reprogramming that occurs in the early embryo and the much less efficient reprogramming that occurs in culture. The capacity to generate pluripotent stem cells has great potential in the modelling and treatment of disease. Understanding the fundamental molecular mechanisms that drive reprogramming will have important implications in our ability to rapidly and reproducibly induce the pluripotent state. Both in culture and in the early embryo, reprogramming requires the activity of specialized transcription factors, termed pioneer factors. Pioneer factors are distinctive in that, unlike other transcription factors, they can bind to DNA in the context of nucleosomes. This feature allows them unique access to the genome and helps to redefine the chromatin accessibility landscape. Nonetheless, it remains unclear what specific functions of pioneer factors are required to drive reprogramming and what the barriers are to pioneer factor-mediated reprogramming. In Drosophila the transcription factor Zelda is required for the initial transcriptional activation of the zygotic genome. We have demonstrated that Zelda possesses essential features of pioneer transcription factors and that this activity is required throughout the process of zygotic genome activation. However, Zelda is unlikely to be working independently, and we have implicated another pioneering factor, GAGA factor, as functioning together with Zelda to define accessible chromatin domains in the early embryo. By combining our development of novel tools to interrogate transcription factor function in the early embryo with the strengths of the well-studied fly system, we are uniquely positioned to determine essential features of reprogramming. We will use genetic, genomic, biochemical, and imaging strategies to 1) define how pioneering factors cooperate to reprogram the zygotic genome, 2) identify chromatin barriers to pioneer factor- mediated reprogramming and 3) determine the role of intrinsically disordered regions in establishing chromatin domains in the early embryo. Our proposed research is significant because by defining essential characteristics of pioneering transcription factors we will identify unifying principles required for efficient reprogramming of specified cells to pluripotency.