Mechanisms of convergence and extension by cell intercalation
Mechanisms of convergence and extension by cell intercalation
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DOI：
10.1098/rstb.2000.0626
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发表时间：
2000-07-29
影响因子：
6.3
通讯作者：
Skoglund, P
中科院分区：
文献类型：
--
作者：
Keller, R;Davidson, L;Skoglund, P
许多胚胎组织的细胞在一维(会聚)上活跃地变窄，在垂直维(延伸)上活跃地延长。会聚和伸展是后生动物形态发生中普遍而重要的组织运动。在脊椎动物中，背轴和近轴的中胚层组织，脊索中胚层和体细胞中胚层会聚并延伸。在两栖动物以及其他一些出现这种运动的生物中，它们是通过中外侧细胞插入发生的，即细胞在内侧轴上的重新排列，以产生在这个轴上更窄，在前后轴上更长的阵列。在两栖动物中，中胚层细胞的嵌入是由两极的、向中间方向的突起活动驱动的，这种活动似乎对相邻的细胞施加牵引力，并将细胞之间相互拉动。此外，脊索-体细胞边界在会聚和延伸中的作用是，当脊索细胞接触边界时，它们会被“捕捉”，从而拉长边界。未来的神经组织也积极地会聚并平行于中胚层延伸。与中胚层不同，神经板中的细胞嵌入通常是通过单极向内侧朝向中线前板底板区域的突起活动而发生的。相反，脊索-底板-底板区域似乎通过附着和被下层脊索拖曳或迁移而收敛和延伸。中胚层的收敛和伸展使其变硬三到四倍，并施加高达0.6mN的力。因此，产生主动力的会聚伸展，即细胞插入的机制，需要一种机制来在保持组织足够的硬度以实质性的力量推动的同时，主动地在彼此之间拉动细胞。在已有证据的基础上，提出了细胞-细胞牵引力的插层模型。这种形态发生机器的基本要素似乎是：(I)两极、内侧定向或单极、内向的突起活动；(Ii)这种突起活动导致细胞彼此之间的内侧定向或内向牵引；(Iii)牵引性突起局限于细胞的末端；(Iv)细胞体的主体上机械稳定的细胞皮质，作为定向或定向细胞牵引的可移动底物。他的模型对细胞黏附、细胞运动和细胞极性的调节以及细胞和组织生物力学的意义进行了讨论。
The cells of many embryonic tissues actively narrow in one dimension (convergence) and lengthen in the perpendicular dimension (extension). Convergence and extension ae ubiquitous and important tissue movements in metazoan morphogenesis. In vertebrates, the dorsal axial and paraxial mesodermal tissues, the notochordal and somitic mesoderm, converge and extend. In amphibians as well as a number of other organisms where these movements appear, they occur by mediolateral cell intercalation, the rearrangement of cell salon the mediolateral axis to produce an array that is narrower in this axis and longer in the anteroposterior axis. In amphibians, mesodermal cell intercalation is driven by bipolar, mediolaterally directed protrusive activity, which appears to exert traction on adjacent cells and pulls the cells between one another. In addition, the notochordal-somitic boundary functions in convergence and extension by 'capturing' notochordal cells as they contact the boundary, thus elongating the boundary. The prospective neural tissue also actively converges and extends parallel with the mesoderm. In contrast to the mesoderm, cell intercalation in the neural plate normally occur by monopolar protrusive activity directed medially, towards the midline notoplate floor-plate region. In contrast, the notoplate-floor-plate region appears to converge and extend by adhering to and being towed by or perhaps migrating on the underlying notochord. Converging and extending mesoderm stiffens by a factor of three or four and exerts up to 0.6 mu N force. Therefore, active force-producing convergent extension, the mechanism of cel intercalation, requires a mechanism to actively pull cells between one another while maintaining a tissue stiffness sufficient to push with a substantial force. Based on the evidence thus far, a cell-cell traction model of intercalation is described. The essential elements of such a a morphogenic machine appear to be (i) bipolar, mediolaterally orientated or monopolar, medially directed protrusive activity; (ii) this protrusive activity results in mediolaterally oriented or medially directed traction of cells on one another; (iii) tractive protrusions are confined to th ends of the cells; (iv) a mechanically stable cell cortex over th bulk of the cell body which serves as a movable substratum for the orientated or directed cell traction. The implications of his model for cell adhesion, regulation of cell motility and cell polarity, and cell and tissue biomechanics are discussed.