ホヤ胚における筋肉細胞分化のメカニズム

抄録

During ascidian embryogenesis, about 42 unicellular striated muscle cells are formed in the tail of the tadpole larva. Lineage of the muscle cells is well documented. Twenty-eight of them are derived from a pair of B4.1 cells of a bilaterally symmetrical 8-cell embryo. This B-line presumptive cells are able to differentiate autonomously into muscle cells without cell-cell interaction depending on so-called muscle determinants localized in the egg myoplasm. In this article we reviewed results of recent analyses on the molecular nature of the muscle determinants, the expression of an ascidian homolog of vertebrate MyoD, and the structure and expression control of a muscle actin gene. All of the results suggest that muscle differentiation in the ascidian embryo is an appropriate experimental system to studying molecular mechanisms of cellular differentiation during animal development.