Division for Morphogenesis, Department of Developmental Biology, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan; Department of Basic Biology, School of Life Science, The Graduate University of Advanced Studies (SOKENDAI), 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan.
Dev Biol. 2013 Oct 15;382(2):482-95. doi: 10.1016/j.ydbio.2013.07.023. Epub 2013 Aug 6.
Gastrulation is a dynamic tissue-remodeling process occurring during early development and fundamental to the later organogenesis. It involves both chemical signals and physical factors. Although much is known about the molecular pathways involved, the roles of physical forces in regulating cellular behavior and tissue remodeling during gastrulation have just begun to be explored. Here, we characterized the force generated by the leading edge mesoderm (LEM) that migrates preceding axial mesoderm (AM), and investigated the contribution of LEM during Xenopus gastrulation. First, we constructed an assay system using micro-needle which could measure physical forces generated by the anterior migration of LEM, and estimated the absolute magnitude of the force to be 20-80nN. Second, laser ablation experiments showed that LEM could affect the force distribution in the AM (i.e. LEM adds stretch force on axial mesoderm along anterior-posterior axis). Third, migrating LEM was found to be necessary for the proper gastrulation cell movements and the establishment of organized notochord structure; a reduction of LEM migratory activity resulted in the disruption of mediolateral cell orientation and convergence in AM. Finally, we found that LEM migration cooperates with Wnt/PCP to form proper notochord. These results suggest that the force generated by the directional migration of LEM is transmitted to AM and assists the tissue organization of notochord in vivo independently of the regulation by Wnt/PCP. We propose that the LEM may have a mechanical role in aiding the AM elongation through the rearrangement of force distribution in the dorsal marginal zone.
原肠作用是胚胎早期发生的一个动态组织重塑过程，对后期器官发生至关重要。它涉及化学信号和物理因素。尽管人们对涉及的分子途径有了很多了解，但物理力在调节原肠作用过程中细胞行为和组织重塑中的作用才刚刚开始被探索。在这里，我们描述了在轴向中胚层（AM）之前迁移的前导中胚层（LEM）产生的力，并研究了 LEM 在 Xenopus 原肠作用中的作用。首先，我们构建了一个使用微针的测定系统，该系统可以测量 LEM 向前迁移产生的物理力，并估计力的绝对值为 20-80nN。其次，激光消融实验表明，LEM 可以影响 AM 中的力分布（即 LEM 沿前后轴在轴向中胚层上施加拉伸力）。第三，发现迁移的 LEM 对于适当的原肠作用细胞运动和有组织的脊索结构的建立是必要的；LEM 迁移活性的降低导致 AM 中中侧细胞方向和汇聚的破坏。最后，我们发现 LEM 迁移与 Wnt/PCP 合作形成适当的脊索。这些结果表明，由 LEM 的定向迁移产生的力被传递到 AM，并协助体内脊索组织的形成，而不受 Wnt/PCP 的调节。我们提出，LEM 可能通过重新排列背侧边缘区的力分布在协助 AM 伸长方面具有机械作用。
