Moore S W, Keller R E, Koehl M A
Department of Integrative Biology, University of California, Berkeley 94720-3140, USA.
Development. 1995 Oct;121(10):3131-40. doi: 10.1242/dev.121.10.3131.
Physically, the course of morphogenesis is determined by the distribution and timing of force production in the embryo and by the mechanical properties of the tissues on which these forces act. We have miniaturized a standard materials-testing procedure (the stress-relaxation test) to measure the viscoelastic properties of the dorsal involuting marginal zone, prechordal mesoderm, and vegetal endoderm of Xenopus laevis embryos during gastrulation. We focused on the involuting marginal zone, because it undergoes convergent extension (an important and wide-spread morphogenetic process) and drives involution, blastopore closure and elongation of the embryonic axis. We show that the involuting marginal zone stiffens during gastrulation, stiffening is a special property of this region rather than a general property of the whole embryo, stiffening is greater along the anteroposterior axis than the mediolateral axis and changes in the cytoskeleton or extracellular matrix are necessary for stiffening, although changes in cell-cell adhesions or cell-matrix adhesions are not ruled out. These findings provide a baseline of data on which future experiments can be designed and make specific, testable predictions about the roles of the cytoskeleton, extracellular matrix and intercellular adhesion in convergent extension, as well as predictions about the morphogenetic role of convergent extension in early development.
从物理角度来看，形态发生的过程由胚胎中力产生的分布和时间以及这些力作用的组织的力学特性所决定。我们将一种标准的材料测试程序（应力松弛测试）进行了小型化处理，以测量非洲爪蟾胚胎原肠胚形成过程中背侧内卷边缘区、脊索前中胚层和植物内胚层的粘弹性特性。我们聚焦于内卷边缘区，因为它会经历汇聚延伸（一个重要且广泛存在的形态发生过程），并驱动内卷、胚孔闭合以及胚胎轴的伸长。我们发现，在原肠胚形成过程中，内卷边缘区会变硬，这种变硬现象是该区域的特殊性质，而非整个胚胎的普遍性质；沿着前后轴的变硬程度大于中外侧轴；并且细胞骨架或细胞外基质的变化对于变硬来说是必要的，不过细胞间黏附或细胞与基质间黏附的变化也不排除在外。这些发现提供了一个数据基线，在此基础上可以设计未来的实验，并对细胞骨架、细胞外基质和细胞间黏附在汇聚延伸中的作用做出具体的、可检验的预测，以及对汇聚延伸在早期发育中的形态发生作用做出预测。
