Actin cytoskeleton from nucleus to organism

项目概要/摘要 教科书告诉我们，肌动蛋白丝赋予细胞形状，蛋白质的“零件清单”驱动着 当细胞改变形状时肌动蛋白重塑。但这种简单的讲述缺少的是一种整体的理解 上游基因表达和信号传导如何控制肌动蛋白重塑， 重塑肌动蛋白，以及下游细胞形状的变化如何转化为及时和可靠的生物体输出， 来了由于肌动蛋白为基础的失败可以源于事件之前，期间和之后重塑，我们需要一个 综合理解肌动蛋白在健康和疾病中的关键作用。 为了获得这种肌动蛋白的“全貌”，我的实验室研究了细胞化， 果蝇胚胎中发生的事件。我们开发了这个简单的实验系统， 驱动细胞化的重塑，同时也将重塑与基因水平的上游事件联系起来， 表达和信号传导，以及下游结果，包括形态发生保真度和胚胎活力。 我们的方法将联合收割机果蝇遗传学和胚胎学与mRNA，肌动蛋白， 和肌动蛋白调节蛋白，低至单分子分辨率。 我们的长期目标是了解肌动蛋白细胞骨架如何与亚细胞过程相互作用 (e.g.转录）和系统（例如细胞核）来协调具有“正确”动力学的细胞形状变化，鲁棒- 和机械性能，以实现成功的有机体结果。未来五年，我们将重点 关于我们正在进行的研究中提出的三个目标：目标1。确定基因表达如何调节肌动蛋白重构 eling -基因表达指导形态发生。然而，我们不知道转录动力学如何告知 肌动蛋白重塑对于细胞化，编码肌动蛋白调节因子的五个基因必须被转录。我们将测试 假设这些基因转录的数量特征支持了全球同步性和一致性， 胚胎细胞化的过程目标2.确定肌动球蛋白收缩的机制-肌动球蛋白收缩 是细胞形态改变所必需的，但其机制存在争议。在细胞化过程中， 在机械上不同的背靠背阶段收缩（肌球蛋白2依赖性与独立性）。我们 将决定肌动蛋白结合蛋白如何驱动每种机制。目标3.确定肌动蛋白细胞骨架 对环境压力的反应-肌动蛋白越来越多地被认为是压力反应的介质。我们- 在胚胎中发现了一种热诱导的肌动蛋白应激反应（ASR）。我们将测试假设， 通过改变细胞质和细胞核中游离肌动蛋白池之间的稳态，使胚胎的生存能力处于危险之中。 这些目标是相互建立的，这样我们就可以理解在此之前、期间和之后的机制 肌动蛋白重塑共同决定胚胎的结果。我们的努力得益于我的实验室 经证实的能力，量化表型和相关事件跨尺度和亚细胞系统。的蛋白质和 我们研究的过程在生物体中是保守的，因此我们的发现将具有广泛的相关性。

PROJECT SUMMARY/ABSTRACT Textbooks teach us that actin filaments give cells their shape, and that a “parts list” of proteins drives actin remodeling when cells change shape. But what is missing from this simple telling is a holistic understanding of how upstream gene expression and signaling control actin remodeling, how different proteins work together to remodel actin, and how downstream cell shape change is converted into timely and reliable organismal out- comes. Because actin-based failures can stem from events before, during and after remodeling, we need an integrated understanding to make sense of actin’s critical role in health and disease. To obtain this kind of “whole picture” view of actin, my lab studies cellularization, the first tissue-building event in Drosophila embryos. We developed this simple experimental system so that we can study the actin remodeling that drives cellularization, while also relating that remodeling to upstream events at the level of gene expression and signaling, and downstream outcomes including morphogenetic fidelity and embryonic viability. Our methods combine Drosophila genetics and embryology with quantitative live-cell imaging of mRNAs, actin, and actin regulatory proteins, down to single-molecule resolution. Our long-term objective is to understand how the actin cytoskeleton interacts with subcellular processes (e.g. transcription) and systems (e.g. nucleus) to orchestrate cell shape change with “the right” kinetics, robust- ness and mechanical properties to achieve successful organismal outcomes. In the next five years, we will focus on three goals arising from our ongoing studies: Goal 1. Determine how gene expression regulates actin remod- eling – Gene expression instructs morphogenesis. Yet, we do not know how transcriptional dynamics inform actin remodeling. For cellularization, five genes that encode actin regulators must be transcribed. We will test a hypothesis that quantitative features of transcription of these genes underpin the global synchrony and uniformity of cellularization in embryos. Goal 2. Determine mechanisms of actomyosin contraction – Actomyosin contraction is essential to cell shape change, but its mechanism is controversial. During cellularization, actomyosin rings contract in back-to-back phases that are mechanistically distinct (Myosin-2 dependent versus independent). We will determine how actin binding proteins drive each mechanism. Goal 3. Determine how the actin cytoskeleton responds to environmental stress – Actin is increasingly recognized as a mediator of stress response. We re- cently identified a heat inducible Actin Stress Response (ASR) in embryos. We will test the hypothesis that ASR puts embryo viability at risk by altering homeostasis between free actin pools in the cytoplasm and nucleus. These goals build on each other so that we will understand how mechanisms before, during and after actin remodeling work together to determine outcomes for the embryo. Our efforts are facilitated by my lab’s proven ability to quantify phenotypes and relate events across scales and subcellular systems. The proteins and processes we study are conserved across organisms so our findings will be broadly relevant.