Temporal control of cell patterning, signaling, and movement in early embryos

果蝇胚胎背腹(DV)轴基因表达的调控 发展模式的范例。顺式调控元件的比较研究 许多研究小组在DV轴上的支持表达清楚地表明 多个转录因子对增强子的组合输入驱动不同 基因表达的空间输出。这种图案化过程的一个关键调节因素是 母系提供的转录因子背部(DL)，NFKB的同源物。DL的功能为 一种以浓度依赖的方式激活靶基因表达的形成剂 DV轴，有助于启动合子基因在 母体到受精卵的转变(MZT)。使用实时成像，我们量化了胚胎中的DL梯度 结果发现，令人惊讶的是，水平不仅在空间上变化，而且随着时间的推移而变化。我们的 上一次供资期间的重点是研究这些动态变化对目标的影响 使用包括活体成像或固定胚胎分析的定量方法进行基因表达 提供时间序列数据的洞察力。在目前的提案中，我们遵循三个新的和令人兴奋的 方向，与早期胚胎中细胞活动的时间有关，并因以下原因而产生 前人的工作。项目1涉及研究广泛表达的激活物和抑制物 配合控制MZT期间合子基因表达的开始。我们假设 广泛表达的抑制物对先驱激活物在控制 染色质的可及性，从而也调节合子基因表达的启动。项目2 重点剖析表达的长基因的短转录本的功能 特别是在合体早期胚胎中。我们假设这些简短的文字记录起到了 以显性-负性变异体的作用调节细胞信号通路激活的时间 信号分子。项目3侧重于确定成纤维细胞生长因子信号转导的机制 调节黏附连接(AJ)及其与肌动蛋白细胞骨架的相互作用 到胚胎中第一次上皮向间充质转化(EMT)；特别是要了解 与成纤维细胞生长因子配体Pyramus相关的退化子如何限制信号传递时间。首要目标是 拟议的研究计划的目的是了解这些细胞活动的时间是如何- 模式、信号和运动--在果蝇胚胎发育中受到控制 并提供适用于高等动物的一般见解。虽然许多研究都集中在 关于基因表达的空间输出，人们对图案形成的时间动态知之甚少。 果蝇胚胎是研究MZT的一个容易处理的系统，因为它在3-4小时内发生，在 相比之下，植入前的哺乳动物胚胎需要几天的时间。果蝇的胚胎是 也适合活体成像和跟踪分析，使其非常适合研究 新生转录和细胞形态。最后，我们建议的研究将提供一般性的 洞察高等动物的早期胚胎发育，因为可能有许多调节机制 保守的。

Regulation of gene expression along the dorsal-ventral (DV) axis of Drosophila embryos serves as a paradigm of developmental patterning. Comparative studies of cis-regulatory elements that support expression along the DV axis from many research groups have made it clear that combinatorial input into enhancers by multiple transcription factors drives distinct spatial-outputs of gene expression. A pivotal regulator of this patterning process is the maternally-provided transcription factor Dorsal (Dl), homolog of NFKB. Dl functions as a morphogen to activate target gene expression in a concentration-dependent manner along the DV axis, contributing to the initiation of zygotic gene expression at the maternal-to-zygotic transition (MZT). Using live imaging, we quantified the Dl gradient in embryos and found, surprisingly, that levels change not only in space but also build in time. Our focus during the previous funding period was to study the impact of these Dl dynamics on target gene expression using quantitative approaches involving analysis of live imaging or fixed embryo time-series data to provide insight. In the current proposal, we follow three new and exciting directions, which relate to the timing of cell actions in early embryos and arose as a result of the previous work. Project 1 involves studying how broadly-expressed activators and repressors cooperate to control the onset of zygotic gene expression during the MZT. We hypothesize that broadly-expressed repressors are equally important to pioneer activators in the control of chromatin accessibility and thereby also regulate initiation of zygotic gene expression. Project 2 focuses on dissecting the function of short-transcripts for long genes that are expressed specifically in the early syncytial embryo. We hypothesize that these short transcripts act to regulate timing of cell signaling pathway activation by functioning as dominant-negative variants of signaling molecules. Project 3 focuses on identifying the mechanism by which FGF signaling regulates adherens junctions (AJs) and their interaction with the actin cytoskeleton to contribute to the first epithelial-to-mesenchymal transition (EMT) in embryos; in particular, to understand how a degron associated with one FGF ligand, Pyramus, limits signaling time. The overarching goal of the proposed research program is to understand how the timing of these cell activities - patterning, signaling, and movement - are controlled in developing Drosophila embryos and to provide general insights applicable to higher animals. While many studies have focused on spatial outputs of gene expression, less is known about the temporal dynamics of patterning. Drosophila embryos are a tractable system to study MZT as it occurs in 3-4 hours, in contrast to taking days in preimplantation mammalian embryos. The Drosophila embryo is also amenable to live in vivo imaging and tracking analyses making it well-suited to the study of nascent transcription and cell morphology. Lastly, our proposed studies will provide general insight into early embryo development of higher animals as many regulatory mechanisms are likely conserved.