Cameron R A, Fraser S E, Britten R J, Davidson E H
Division of Biology, California Institute of Technology, Pasadena 91125.
Development. 1989 Aug;106(4):641-7. doi: 10.1242/dev.106.4.641.
Several lines of evidence suggest that the oral-aboral axis in Strongylocentrotus purpuratus embryos is specified at or before the 8-cell stage. Were the oral-aboral axis specified independently of the first cleavage plane, then a random association of this plane with the blastomeres of the four embryo quadrants in the oral-aboral plane (viz. oral, aboral, right and left) would be expected. Lineage tracer dye injection into one blastomere at the 2-cell stage and observation of the resultant labeling patterns demonstrates instead a strongly nonrandom association. In at least ninety percent of cases, the progeny of the aboral blastomeres are associated with those of the left lateral blastomeres and the progeny of the oral blastomeres with the right lateral ones, respectively. Thus, ninety percent of the time the oral pole of the future oral-aboral axis lies 45 degrees clockwise from the first cleavage plane as viewed from the animal pole. The nonrandom association of blastomeres after labeling of the 2-cell stage implies that there is a mechanistic relation between axis specification and the positioning of the first cleavage plane.
几条证据表明，紫海胆胚胎的口-反口轴在8细胞期或之前就已确定。如果口-反口轴的确定独立于第一次卵裂平面，那么该平面与口-反口平面（即口面、反口面、右侧和左侧）四个胚胎象限的卵裂球之间的关联将是随机的。在2细胞期向一个卵裂球注射谱系追踪染料，并观察由此产生的标记模式，结果显示出强烈的非随机关联。在至少90%的情况下，反口面卵裂球的后代分别与左侧卵裂球的后代相关联，口面卵裂球的后代与右侧卵裂球的后代相关联。因此，从动物极观察，未来口-反口轴的口极有90%的概率位于第一次卵裂平面顺时针45度处。2细胞期标记后卵裂球的非随机关联意味着轴的确定与第一次卵裂平面的定位之间存在机制上的关系。
