Dynamic regulatory mechanisms of robust pattern formation in the neural tube

摘要 我们研究的长期目标是了解允许发育系统 稳健地构建正确模式、形状和大小的胚胎。开发系统面临着各种各样的 来自不同来源的变化，包括环境，遗传和随机，表现在多个 从分子到细胞再到器官。面对这些挑战，生物体被设计成 通过进化来缓冲这些变异的表型，以稳健地实现发育 规范，沃丁顿称之为渠道化的过程。因为我们对细胞的分子和细胞细节的了解 图案系统已经扩展，现在有机会了解系统级机制 从而形成稳健的图案。在这里，我们通过缩放的透镜关注模式鲁棒性， 尺寸控制。缩放是一个显着的过程，其中图案的大小可以调整到可用的大小。 组织的大小。自汉斯·德里施（Hans Driesch）以来，鳞片的生长一直令胚胎学家着迷， 1885年发现，当分离两细胞期海胆胚胎的卵裂球时， 两个不完整的胚胎，而是两个完整的胚胎，其中所有的图案都被减半。类似的结果 已经在各种生物体中发现，但是产生大小所需的外科手术操作- 减少动物通常是困难的，并导致许多变化，从而限制了定量研究。 最近，我们已经开发出一种新的方法来产生不同大小的斑马鱼卵， 可复制的这样的胚胎具有质量正常但规模化的模式，并且可以产生可行的成年人。 在分子水平上，我们发现大多数基因表达模式（例如形态发生素及其靶点）随 然而，一小部分基因，即感知组织大小以调节缩放的基因， (e.g.通过与形态发生素相互作用），则不会。因此，这些大小改变的胚胎代表了一种强大的， 独特的方法来识别和确定模式缩放的机制。最终，组织大小 通过平衡发育过程中的增殖和分化速率来确定。我们有 发现神经管的增殖与分化平衡处于负反馈控制之下 通过机械压力/组织填塞。在这里，我们将使用定量成像，分子和 机械扰动和计算机建模，以确定系统级机制，允许：1） 形态发生基图案化以缩放以适应可用空间，以及2）增殖和分化速率被 平衡以使组织生长以适应可用空间。这些问题将在 斑马鱼的神经管，但我们希望由此产生的机制是广泛适用的。这种集成 理解对于诊断和治疗出生缺陷如神经管缺陷和在新生儿中的应用是重要的。 合理设计工程组织。

Abstract The long-term goal of our research is to understand the principles that permit developmental systems to robustly construct embryos of the correct pattern, shape, and size. Developmental systems face a gamut of variations from different sources including environmental, genetic, and stochastic, which manifest at multiple levels from molecules to cells to organs. In the face of these challenges, organisms have been designed through evolution to buffer the phenotype against these variations in order to robustly achieve a developmental norm, a process Waddington termed canalization. As our knowledge of the molecular and cellular details of patterning systems has expanded, there is now the opportunity to understand the systems level mechanisms that give rise to robust pattern formation. Here we focus on pattern robustness through the lens of scaling and size control. Scaling is a remarkable process in which the size of a pattern can be adjusted to the available size of the tissue. Scaling has fascinated and baffled embryologists since the time of Hans Driesch who in 1885 found that when the blastomeres of a two-cell stage sea urchin embryo are separated, the result is not two partial embryos but rather two complete embryos in which all their pattern is scaled by half. Similar results have since been found in a variety of organisms, but the surgical manipulations required to generate size- reduced animals are generally difficult and result in a lot of variability, thus limiting quantitative investigation. Recently, we have developed a new method for generating zebrafish eggs of different size that is robust and reproducible. Such embryos have qualitatively normal but scaled patterning and can give rise to viable adults. At a molecular level we find that most gene expression patterns (e.g. morphogens and their targets) scale with the tissues they pattern; however, a small subset of genes, the ones that sense tissue size to regulate scaling (e.g. by interacting with morphogens), do not. Thus, these size altered embryos represent a powerful and unique method to identify and determine the mechanisms of pattern scaling. Ultimately, tissue size is determined by balancing the rates of proliferation and differentiation over the course of development. We have found that the balance of proliferation and differentiation in the neural tube is under negative feedback control by mechanical pressure/tissue packing. Here we will use a combination of quantitative imaging, molecular and mechanical perturbations, and computer modeling to determine the systems-level mechanisms that allow: 1) morphogen patterning to scale to fit the available space, and 2) proliferation and differentiation rates to be balanced to cause a tissue to grow to fit the available space. These questions will be addressed in the zebrafish neural tube, but we expect the resulting mechanisms to be widely applicable. Such an integrated understanding is important for diagnosing and treating birth defects such as neural tube defects and in the rational design of engineered tissues.