Venuti J M, Jeffery W R
Department of Zoology, University of Texas, Austin 78712.
Int J Dev Biol. 1989 Jun;33(2):197-212.
A detailed cell lineage of ascidian embryos has been available since the turn of the century. This cell lineage was deduced from the segregation of pigmented egg cytoplasmic regions into particular blastomeres during embryogenesis. The invariant nature of the cell lineage, the segregation of specific egg cytoplasmic regions into particular blastomeres, and the autonomous development of most embryonic cells suggests that cell fate is determined primarily by cytoplasmic determinants. Modern studies have provided strong evidence for the existence of cytoplasmic determinants, especially in the primary muscle cells, yet the molecular identity, localization, and mode of action of these factors are still a mystery. Recent revisions of the classic cell lineage and demonstrations of the lack of developmental autonomy in certain embryonic cells suggest that induction may also be an important mechanism for the determination of cell fate in ascidians. There is strong evidence for the induction of neural tissue and indirect evidence for inductive interactions in the development of the secondary muscle cells. In contrast to the long-accepted dogma, specification of cell fate in ascidians appears to be established by a combination of cytoplasmic determinants and inductive cell interactions.
自世纪之交以来，海鞘胚胎的详细细胞谱系就已为人所知。这种细胞谱系是从胚胎发育过程中有色卵细胞质区域向特定卵裂球的分离推导出来的。细胞谱系的不变性、特定卵细胞质区域向特定卵裂球的分离以及大多数胚胎细胞的自主发育表明，细胞命运主要由细胞质决定因素决定。现代研究为细胞质决定因素的存在提供了有力证据，尤其是在初级肌肉细胞中，但这些因素的分子身份、定位和作用方式仍是一个谜。最近对经典细胞谱系的修订以及某些胚胎细胞缺乏发育自主性的证明表明，诱导也可能是海鞘中细胞命运决定的重要机制。有强有力的证据表明神经组织的诱导以及次级肌肉细胞发育中诱导相互作用的间接证据。与长期以来被接受的教条相反，海鞘中细胞命运的特化似乎是由细胞质决定因素和诱导性细胞相互作用共同建立的。
