Molecular control of mechanical forces driving buckling morphogenesis of the small intestine

项目总结/摘要 这项工作的广泛目标是了解分子线索如何与物质协调和相互作用 驱动脊椎动物形态发生的力量。具体来说，我们专注于循环的小肠，一个过程 必不可少的包装的冗长的肠道内的腹部，当有缺陷导致毁灭性的 先天性疾病由于肠管弯曲，当它抵抗肠壁的约束而伸长时， 其附着的肠系膜。由此产生的环路波长和曲率可以从一些 实验测量的物理性质，包括组织几何形状、生长速率和硬度。屈曲 已经成为塑造胚胎中各种组织和器官的核心机制。然而，优雅的 屈曲力学的简单性往往暴露了产生和限制这种屈曲的生物学复杂性。 物理过程。事实上，对屈曲形态发生的理解，将物理学与物理学相结合， 在大多数情况下，缺乏潜在的分子线索和动态细胞行为。我们最近发现骨形态发生蛋白 信号传导是控制肠道循环的关键途径。利用这一途径，本申请利用了一种方法， 对相关力学的良好理解，以研究分子和细胞生物控制， 屈曲形态发生，以及如何在发展过程中产生的力量反馈，以调节这些 对照我们开始通过询问肠系膜中BMP依赖的肌动蛋白活性如何促进组织 力学通过操纵细胞外基质组织（目的1），重点是这种能力， 组织在硬化之前适应大应变（>100%）;这种行为，称为组成性 非线性，是一个关键的决定因素循环形态，但其生物学基础和形态功能， 在发展中往往被忽视。接下来，我们以BMP建立的惊人观察为基础 通过以增殖非依赖性方式限制肠系膜伸长的差异生长（目标2），测试 假设BMP调节细胞大小以建立差异生长，从而驱动屈曲。目标1 和2集中于肠系膜内的弹性能量储存的BMP依赖性机制。这种能量 存储必须与能量耗散精确平衡以产生定型循环。为了解决这一问题， 我们研究了肠系膜增殖生长的控制（Aim 3），重点是Hippo信号传导， 途径以及差异生长产生的力量如何反馈增殖。这些十字架- 学科研究结合了联合收割机逆转录病毒基因的错误表达，细胞行为，力和刚度的分析 测量、拉伸生物反应器研究和数学建模。长远目标是建立 机械分子规则或胚胎发生的设计原则，使真正的工程方法， 再生医学，其中刚度，应力和应变可以与细胞类型一起生物编程 本发明的目的在于提供一种用于指导功能性三维组织和器官的组装的技术规范。

PROJECT SUMMARY/ABSTRACT The broad goal of this work is to understand how molecular cues orchestrate and interact with the physical forces to drive vertebrate morphogenesis. Specifically, we focus on looping of the small intestine, a process essential for packing of the lengthy intestine within the abdomen, that when defective leads to devastating congenital disorders. Loops arise due to buckling of the intestinal tube as it elongates against the constraint of its attached mesentery. The resulting loop wavelength and curvature can be predicted from a handful of experimentally measured physical properties, comprising tissue geometry, growth rate, and stiffness. Buckling has emerged as a core mechanism of shaping various tissues and organs in the embryo. However, the elegant simplicity of buckling mechanics often betrays the biological complexity that engenders and constrains this physical process. Indeed, an understanding of buckling morphogenesis that integrates physics with the underlying molecular cues and dynamic cell behaviors is lacking in most contexts. We recently identified BMP signaling as a key pathway controlling gut looping. With this pathway in hand, the present application exploits a well-developed understanding of the associated mechanics to study the molecular and cell biological control of buckling morphogenesis, as well as how forces generated during development feed back to modulate these controls. We begin by asking how BMP-dependent acto-myosin activity in the mesentery contributes to tissue mechanics through manipulation of extracellular matrix organization (Aim 1), focusing on the ability of this tissue to accommodate large strains (>100%) before stiffening; this behavior, known as constitutive nonlinearity, is a critical determinant of looping morphology, but its biological basis and morphological function are often overlooked in development. Next, we build upon the striking observation that BMP establishes differential growth by restricting mesentery elongation in a proliferation-independent manner (Aim 2), testing the hypothesis that BMP regulates cell size to set up differential growth, driving buckling. Therefore, Aims 1 and 2 focus on BMP-dependent mechanisms of elastic energy storage within the mesentery. This energy storage must be precisely balanced with energy dissipation to generate stereotyped looping. To address this, we examine the control of proliferative growth of the mesentery (Aim 3), focusing on the Hippo signaling pathway and how forces generated by differential growth may feedback on proliferation. These cross- disciplinary studies combine retroviral gene misexpression, analyses of cell behavior, force and stiffness measurements, tensile bioreactor studies, and mathematical modeling. The long term vision is to establish mechano-molecular rules or design principles of embryogenesis, enabling a true engineering approach to regenerative medicine, wherein stiffness, stress, and strain can be biologically programmed alongside cell type specification to instruct the assembly of functional three dimensional tissues and organs.