Nishikata T, Satoh N
Department of Zoology, Faculty of Science, Kyoto University, Japan.
Cell Differ Dev. 1990 Apr;30(1):43-53. doi: 10.1016/0922-3371(90)90073-6.
Among 40 notochord cells of an ascidian tadpole larva, 32 notochord cells originate from the anterior-vegetal blastomeres (the A4.1 pair) of an 8-cell embryo and eight cells originate from the posterior-vegetal blastomeres (the B4.1 pair), but the animal blastomeres (the a4.2 and b4.2 pairs) are not engaged in the formation of the notochord. If four pairs of cells, separated from an 8-cell embryo, were allowed to develop into quarter embryos, expression of the notochord-specific antigen was evident in the A4.1 and B4.1 quarter embryos. Embryos, in which cytokinesis had been permanently blocked at the 8-cell and later stages with cytochalasin B, were found to develop the notochord-specific antigen only in the presumptive notochord cells. These findings suggest the developmental autonomy of presumptive notochord cells in the ascidian embryo.
在海鞘蝌蚪幼虫的40个脊索细胞中，32个脊索细胞起源于8细胞胚胎的前侧植物性卵裂球（A4.1对），8个细胞起源于后侧植物性卵裂球（B4.1对），但动物性卵裂球（a4.2和b4.2对）不参与脊索的形成。如果将从8细胞胚胎分离出的四对细胞培养成四分之一胚胎，则在A4.1和B4.1四分之一胚胎中可明显检测到脊索特异性抗原的表达。用细胞松弛素B在8细胞及后续阶段永久性阻断胞质分裂的胚胎，仅在假定的脊索细胞中发育出脊索特异性抗原。这些发现表明海鞘胚胎中假定的脊索细胞具有发育自主性。
