Quantitative analysis of signaling dynamics across the BMP morphogen gradient

摘要 我们目前对BMP信号通路特异性的了解是基于基础遗传和体外实验 实验，但我们对细胞如何产生不同但特异的反应了解有限 体内也有类似的信号输入。在果蝇胚胎中，BMP信号的陡峭梯度是动态的 在原肠形成之前建立的。这种梯度由不同的细胞群体解释，以建立 胚胎的背腹轴，背中线上的细胞开启一组独特的转录本 与更多的侧向细胞相比。我们不知道梯度的形成和最终的动力学 胚胎中的一群细胞解释梯度模式，以产生正确的时空 转录反应。使用新的成像工具和量化系统级别的方法，我将能够 询问BMP信号通路的上游输入是如何在细胞核中解码以获得正确的 时空转录反应。 在这项研究中，我将探索BMP信号编码的两种潜在机制。一、新办法 将使我能够分析沿着BMP梯度的通路活动的信号动力学。有了这些数据我 我将建立一个输入-输出关系模型来预测驱动BMP反应的机制 转录动力学。其次，我将确定配基和受体对的不同组合是否会发挥作用 在说明和解释骨形态发生蛋白梯度中的作用。我将研究动态和组合 信号被用来在胚胎中产生BMP信号反应的野生型模式。然后，使用 在传播和塑造形态形成梯度的关键途径组件中的遗传扰动，我将 测试动态和组合信号中的这些输入-输出关系是否适用于不同的BMP 信令上下文。这项研究的成功完成将为如何保护 信号通路是由体内细胞跨越时间和空间进行解释的。

ABSTRACT Our current knowledge of BMP signaling pathway specificity is based upon foundational genetic and in vitro experiments, but we have limited understanding as to how cells produce diverse but specific responses to similar signaling inputs in vivo. In the Drosophila embryo, a steep gradient of BMP signaling is dynamically established prior to gastrulation. This gradient is interpreted by different populations of cells to establish the dorsal-ventral axis of the embryo, with cells at the dorsal midline turning on a unique set of transcripts compared to more lateral cells. We do not know how the dynamics of gradient formation and the final gradient pattern are interpreted by cohorts of cells in the embryo to produce the correct spatiotemporal transcriptional response. Using new imaging tools and a quantitative systems level approach, I will be able to interrogate how upstream inputs to the BMP signaling pathway are decoded in the nucleus to elicit correct spatiotemporal transcriptional responses. In this study I will explore two potential mechanisms by which BMP signaling is encoded. First, new methods will allow me to assay the signaling dynamics of pathway activity along the BMP gradient. With these data I will build an input-output relationship model to predict the mechanisms that drive BMP-responsive transcriptional dynamics. Second, I will determine if different combinations of ligand and receptor pairs play a role in specification and interpretation of the BMP gradient. I will study how both dynamic and combinatorial signaling are used to produce the wild type pattern of BMP signaling responses in the embryo. Then, using genetic perturbations in key pathway components that propagate and shape the morphogen gradient, I will test if these input-output relationships in dynamics and combinatorial signaling hold true across different BMP signaling contexts. Successful completion of this study will provide a quantitative view for how a conserved signaling pathway is interpreted by cells in vivo across time and space.