Kawaminani S, Nishida H
Department of Life Sciences, Tokyo Institute of Technology, Yokohama, Japan.
Dev Biol. 1997 Jan 1;181(1):14-20. doi: 10.1006/dbio.1996.8442.
The tadpole larvae of the ascidian Halocynthia roretzi have trunk lateral cells (TLCs) in their trunk. TLCs give rise to adult blood cells after metamorphosis. TLCs are exclusively derived from the A7.6 cell pair of 64-cell embryos. When prospective TLC blastomeres were isolated from embryos before the 16-cell stage, they failed to express TLC-specific antigen, a molecular indication of differentiation of TLCs. Isolates after the 32-cell stage, however, autonomously expressed the antigen. Results of experiments involving coisolation and recombination of blastomeres at the 16-cell stage showed that the inductive influence emanating from cells of animal hemisphere (presumptive epidermis blastomeres) is required for TLC formation. The inductive interaction takes place at the 16-cell stage, two cell cycles before the developmental fate becomes exclusively restricted to TLC formation. The inducing activity is distributed widely in animal hemisphere. By contrast, only presumptive TLC blastomeres have competence to be induced to form TLCs.
海鞘（Halocynthia roretzi）的蝌蚪幼虫在其躯干部位有躯干侧细胞（TLCs）。变态后，TLCs会发育成成体血细胞。TLCs仅源自64细胞胚胎的A7.6细胞对。当在16细胞期之前从胚胎中分离出预期的TLC卵裂球时，它们无法表达TLC特异性抗原，这是TLCs分化的一种分子指示。然而，在32细胞期之后分离出的细胞能自主表达该抗原。在16细胞期进行卵裂球共分离和重组的实验结果表明，TLC形成需要来自动物半球细胞（假定的表皮卵裂球）的诱导作用。这种诱导相互作用发生在16细胞期，即发育命运完全限定为形成TLCs的两个细胞周期之前。诱导活性在动物半球广泛分布。相比之下，只有假定的TLC卵裂球有被诱导形成TLCs的能力。
