Cellular and Molecular Events in Early Leech Development

舌管水蚤胚胎，如三叶虫的胚胎，非常适合研究早期发育的细胞方面，因为它们相对较大和耐寒，而且它们的卵裂球既可以通过实验获得，也可以单独识别。因此，可以对从一个胚胎到下一个胚胎的发育相同的细胞进行实验分析。这一建议将继续先前对水蚤发育的各个方面的分析，包括：细胞质决定因素在决定早期卵裂中的作用；中胚层和外胚层细胞系的指定；命运决定最初相等的细胞之间的相互作用；发育细胞谱系的持续完善；瞬时胚胎上皮对形态发生的影响。拟议的实验将在细胞和分子水平上进行这些分析，将“反向遗传方法”的技术与以前使用的技术相结合，例如将细胞谱系示踪剂和其他材料显微注射到已确定的胚胎细胞、单细胞消融和光学显微镜。

Glossiphoniid leech embryos, such as those of the species Helobdella triserialis, are well suited for studying cellular aspects of early development, because they are relatively large and hardy, and because their blastomeres are both experimentally accessible and individually identifiable. Thus, experimental analyses can be carried out on developmentally equivalent cells from one embryo to the next. This proposal is to continue previous analyses of various aspects of leech development, including: the role of cytoplasmic determinants in determining early cleavage; the specification of mesodermal and ectodermal cell lines; fate determining interactions between initially equipotent cells; the continuing refinement of developmental cell lineages; the influence of a transient embryonic epithelium on morphogenesis. The experiments proposed will carry out these analyses at the cellular and molecular level, by incorporating the techniques of the "reverse genetic approach" in combination with those used previously, such as microinjection of cell lineage tracers and other materials into identified embryonic cells, single cell ablation and optical microscopy.