Wessel G M, Wikramanayake A
Department of Molecular and Cell Biology and Biochemistry, Brown University, Providence, Rhode Island 02912, USA.
Bioessays. 1999 Jun;21(6):459-71. doi: 10.1002/(SICI)1521-1878(199906)21:6<459::AID-BIES3>3.0.CO;2-Y.
Gastrulation is the process of early development that reorganizes cells into the three fundamental tissue types of ectoderm, mesoderm, and endoderm. It is a coordinated series of morphogenetic and molecular changes that exemplify many developmental phenomena. In this review, we explore one of the classic developmental systems, the sea urchin embryo, where investigators from different backgrounds have converged on a common interest to study the origin, morphogenesis, and developmental regulation of the endoderm. The sea urchin embryo is remarkably plastic in its developmental potential, and the endoderm is especially instructive for its morphological and molecular responsiveness to inductive cell interactions. We start by examining and integrating the several models for the morphogenetic mechanisms of invagination and tissue elongation, the basic processes of endoderm morphogenesis in this embryo. We next critique the proposed mechanisms of inductive gene regulation in the endoderm that exemplifies a concept of modular transcriptional regulation. Finally, we end with an examination of the current molecular models to explain cell fate determination of the endoderm. Recent progress at the molecular level should soon allow us to explain the seminal experimental observations made in this embryo over a hundred years ago.
原肠胚形成是早期发育过程，它将细胞重新组织成外胚层、中胚层和内胚层这三种基本组织类型。这是一系列协调的形态发生和分子变化，体现了许多发育现象。在本综述中，我们探讨经典发育系统之一——海胆胚胎，来自不同背景的研究人员汇聚于此，共同研究内胚层的起源、形态发生和发育调控。海胆胚胎在发育潜能方面具有显著的可塑性，而内胚层对诱导性细胞相互作用的形态和分子反应特别具有指导意义。我们首先研究并整合了关于内陷和组织伸长的形态发生机制的几种模型，这是该胚胎内胚层形态发生的基本过程。接下来，我们对提出的内胚层诱导基因调控机制进行批判，该机制体现了模块化转录调控的概念。最后，我们以对当前分子模型的研究结束，以解释内胚层细胞命运的决定。分子水平上的最新进展应该很快使我们能够解释一百多年前在这个胚胎中所做的开创性实验观察结果。
