Molecular drivers of tissue-specific morphogenetic programs

项目总结 先天畸形或先天缺陷是导致美国儿童死亡的主要原因 九个人中。神经管缺陷(NTD)是最常见和最具破坏性的先天性畸形之一， 这是由于神经管在早期胚胎发育过程中未能关闭所致。神经管闭合 不仅要求成对的神经皱折抬高并融合在一起，还要求神经外胚层 (神经管的前身)，缩窄到足以使神经皱褶沿着中线相遇。这一点至关重要 狭窄在原肠形成期间开始，并耦合到 神经外胚层，由细胞极化重排成更长更窄的排列而成。这 过程，恰当地称为收敛和扩张(C&E)，是一个高度保守的形态发生 在形成大量胚胎组织和制定动物身体计划方面具有重要作用的机制。 神经管的闭合和初级AP胚轴的延长是由 神经外胚层和潜在的中胚层，每一个都表现出一套不同的细胞行为和 积极促进中轴线延伸。然而，人们对组织同一性是如何协调的仍知之甚少 通过组织特定的细胞行为程序。 在这里，我们讨论了斑马鱼轴线延伸的组织特异性形态发生，一个模型 脊椎动物胚胎。我们最近报道，转化生长因子-家族的形态原结节不仅是 C&E在斑马鱼中的原肠运动，但也足以促进这些细胞的行为 幼稚的斑马鱼胚胎外植体。通过改变节点信号激活的方法，我们可以驱动组织- 这些外植体中的神经外胚层或中胚层的特异性C&E。重要的是，这使我们能够 分离单个组织层的形态发生并区分控制细胞特性的机制 与那些控制细胞运动的细胞不同。每一种C&E模式都与特定的发育高峰有关 结节活动和转录图谱，使我们假设结节活动的时间模式 通过不同的下游分子程序定义组织特定的形态发生。使用尖端技术 光遗传学方法精确地操纵节点活动，目标1中提出的实验将测试如何 时间信号动力学的变化在体内和体外都控制着组织特异性的C&E。在目标2和目标3中，我们 将定义每个节点依赖的基因表达程序所需的特定组件 和/或分别足以满足中胚层和神经外胚层的组织特异性C&E。这项建议 利用我们创新的外植体模型和光遗传方法的独特优势来识别 在轴延伸中具有新作用的基因，从而促进了对神经管的基本理解 封闭对于改善NTDS的诊断、预防和治疗策略至关重要。

Project summary Congenital malformations, or birth defects, are the leading cause of death of American children under the age of nine. Neural tube defects (NTDs) are among the most common and devastating congenital malformations, and result from a failure of the neural tube to close during early embryonic development. Neural tube closure requires not only that the paired neural folds raise and fuse together, but also that the neuroectoderm (precursor to the neural tube), narrows sufficiently for the neural folds to meet along the midline. This critical narrowing begins during gastrulation and is coupled to a concurrent anteroposterior (AP) extension of the neuroectoderm that results from the polarized rearrangement of cells into a longer and narrower array. This process, appropriately termed convergence & extension (C&E), is a highly conserved morphogenetic mechanism with essential roles in shaping numerous embryonic tissues and establishing the animal body plan. Neural tube closure and extension of the primary AP embryonic axis are driven by C&E of both the neuroectoderm and the underlying mesoderm, each of which exhibits a distinct suite of cell behaviors and contributes actively to axis extension. It remains poorly understood, however, how tissue identity is coordinated with tissue-specific cell behavior programs. Here, we address the tissue-specific morphogenesis underlying axis extension in zebrafish, a model vertebrate embryo. We recently reported that the TGF- family morphogen Nodal is not only necessary for C&E gastrulation movements in zebrafish, but also sufficient to promote these cell behaviors in otherwise naïve zebrafish embryonic explants. By varying the method of Nodal signaling activation, we can drive tissue- specific C&E of either the neuroectoderm or mesoderm within these explants. Importantly, this allows us to uncouple morphogenesis of individual tissue layers and distinguish the mechanisms that control cell identity from those that control cell movement. Each mode of C&E is associated with a specific developmental peak of Nodal activity and transcriptional profile, leading us to hypothesize that temporal patterns of Nodal activity define tissue-specific morphogenesis via distinct downstream molecular programs. Using cutting-edge optogenetic approaches to precisely manipulate Nodal activity, experiments proposed in Aim 1 will test how variations in temporal signaling dynamics control tissue-specific C&E both in and ex vivo. In Aims 2 and 3, we will define the specific components of each Nodal-dependent gene expression program that are necessary and/or sufficient for tissue-specific C&E of the mesoderm and neuroectoderm, respectively. This proposal leverages the unique advantages of our innovative explant model and optogenetic approaches to identify genes with novel roles in axis extension, thereby advancing a fundamental understanding of neural tube closure essential for improved diagnosis, prevention, and treatment strategies for NTDs.