Mechanisms of genomic reprogramming and transcriptional activation in the embryo

 描述（由申请人提供）：我们的长期目标是阐明控制基因组重组的分子机制，该基因组重组允许从特定细胞类型过渡到全能状态。这种转变在受精后立即迅速有效地发生，在胚胎发育的初始阶段。在这个关键的发育阶段，合子基因组是转录静止的。只有当细胞变得全能并准备分化时，广泛的合子转录才开始。尽管合子基因组的这种延迟的转录激活几乎是 这一过程在后生动物中具有普遍性，但支配这一过程的机制以及它与协调建立全能状态的关系仍不清楚。我们最近已经证明，果蝇蛋白塞尔达（ZLD）的全球行动，以促进合子基因组的激活，并提出它是这样做，通过建立一个允许的染色质环境。通过全基因组结合研究，我们已经表明ZLD在发育早期与数千个基因组区域结合，这些区域随后驱动合子转录的第一波。这些基因座后来被定义为开放染色质区域，并被大量控制胚胎模式的转录因子结合。通过我们的初步研究，我们很好地定位，以确定合子基因组被重塑，创造一个环境允许转录激活和细胞分化的机制。我们将使用遗传学，基因组学和生物化学策略来确定ZLD作为先驱因子塑造早期胚胎染色质环境的机制：1）确定ZLD在组织早期胚胎染色质结构中的作用，2）确定ZLD介导的基因组激活所需的辅助因子。我们将获得的ZLD功能的机械见解将促进我们对全能基因组如何建立的理解。最终，这项工作将产生全能哺乳动物干细胞在培养和体内的重要影响。

 DESCRIPTION (provided by applicant): Our long-term goal is to elucidate the molecular mechanisms governing the restructuring of the genome that allows for the transition from a specified cell type to a totipotent state. This transition occurs rapidly and efficiently immediatey following fertilization, during the initial stages of embryonic development. At this critical developmental stage, the zygotic genome is transcriptionally quiescent. Only when the cells have become totipotent and poised to differentiate does widespread zygotic transcription initiate. Despite the fact that this delayed transcriptional activation of zygotic genome is nearly universal among metazoans, the mechanisms governing this process and how it relates to the coordinated establishment of a totipotent state remain unknown. We have recently demonstrated that the Drosophila protein Zelda (ZLD) acts globally to facilitate the activation of the zygotic genome and propose that it is doing so by establishing a permissive chromatin environment. Through genome-wide binding studies, we have shown that ZLD is bound early in development to thousands of genomic regions that subsequently drive the first wave of zygotic transcription. These loci are later defined as regions of open chromatin and are bound by a large number of transcription factors that govern embryonic patterning. Through our initial studies, we are well positioned to define the mechanisms by which the zygotic genome is remodeled to create an environment permissive to transcriptional activation and cellular differentiation. We will use genetic, genomic, and biochemical strategies to determine the mechanism by which ZLD is acting as a pioneer factor to shape the chromatin environment of the early embryo by: 1) determining the role of ZLD in organizing the chromatin structure of the early embryo and 2) identifying cofactors required for ZLD-mediated genome activation. The mechanistic insights we will gain into ZLD function will advance our understanding of how totipotent genomes are established generally. Ultimately this work will have important implications for the generation of totipotent mammalian stem cells both in culture and in vivo.