大部分动物胚胎通过身体后部一个生长区的细胞积累来生长，但控制生长的形成及方向性的形态发生力量却不知道。
根据对在鸡胚胎中躯干和尾巴结构的形成过程中的轴伸长所做的一项研究，Bénazéraf等人提出，响应于由FGF生长因子调控的信号作用而发生的组织伸长，是由对分级的、随机的细胞运动的集体调控而出现的一个特性，而不是由对个别细胞运动的方向性的调控所出现的一个特性。(生物谷Bioon.net)
生物谷推荐原文出处：
Nature doi:10.1038/nature09151
A random cell motility gradient downstream of FGF controls elongation of an amniote embryo
Bertrand Bénazéraf,Paul Francois,Ruth E. Baker,Nicolas Denans,Charles D. Little& Olivier Pourquié
Vertebrate embryos are characterized by an elongated antero-posterior (AP) body axis, which forms by progressive cell deposition from a posterior growth zone in the embryo. Here, we used tissue ablation in the chicken embryo to demonstrate that the caudal presomitic mesoderm (PSM) has a key role in axis elongation. Using time-lapse microscopy, we analysed the movements of fluorescently labelled cells in the PSM during embryo elongation, which revealed a clear posterior-to-anterior gradient of cell motility and directionality in the PSM. We tracked the movement of the PSM extracellular matrix in parallel with the labelled cells and subtracted the extracellular matrix movement from the global motion of cells. After subtraction, cell motility remained graded but lacked directionality, indicating that the posterior cell movements associated with axis elongation in the PSM are not intrinsic but reflect tissue deformation. The gradient of cell motion along the PSM parallels the fibroblast growth factor (FGF)/mitogen-activated protein kinase (MAPK) gradient1, which has been implicated in the control of cell motility in this tissue2. Both FGF signalling gain- and loss-of-function experiments lead to disruption of the motility gradient and a slowing down of axis elongation. Furthermore, embryos treated with cell movement inhibitors (blebbistatin or RhoK inhibitor), but not cell cycle inhibitors, show a slower axis elongation rate. We propose that the gradient of random cell motility downstream of FGF signalling in the PSM controls posterior elongation in the amniote embryo. Our data indicate that tissue elongation is an emergent property that arises from the collective regulation of graded, random cell motion rather than by the regulation of directionality of individual cellular movements.
