Early Events in Leech Embryogenesis

舌管水蚤Helobdella triserialis的胚胎非常适合研究早期发育的细胞事件，因为它们很大，很耐寒，含有可识别的细胞，可以进行许多类型的实验操作。这些胚胎表现出许多在高等真核生物发育过程中具有普遍意义的现象，包括细胞质决定因素、核和有丝分裂纺锤体的定向运动、卵裂和干细胞分裂的不同阶段、胚胎化、谱系依赖和位置依赖命运决定的可分离实例，以及上皮细胞的相互作用。这里提出的研究将使用多种技术，例如：细胞谱系示踪剂、光敏染料、药物和放射化学物质的显微注射；原位杂交；免疫组织化学；凝胶电泳；放射自显影；延时视频记录；以及微光荧光显微镜。从这些研究中，应该能够更详细地描述各种发育过程及其运作机制。此外，通过研究同一物种中若干平行的发育过程，希望能对基本细胞和发育过程相互作用的更高层次机制有一些了解。例如，这个项目的一部分将研究第一次卵裂前特殊细胞质结构域的形成，以及它们如何影响第一次卵裂的对称性。另一个部分将检验遗传RNA调节细胞分裂模式变化的假设。个体细胞如何在早期胚胎发育过程中获得其特定的命运是发育生物学的一个基本问题。魏斯布拉特博士以水蚤为模型系统，提出了一系列实验，以确定是什么影响了胚胎的细胞谱系。

Embryos of the glossiphoniid leech Helobdella triserialis are well suited for studying cellular events in early development, because they are large, hardy, and contain identifiable cells that are accessible for many sorts of experimental manipulations. These embryos exhibit many phenomena that are of general significance in the development of higher eukaryotes, including cytoplasmic determinants, directed movements of nuclei and mitotic spindles, distinct phases of cleavage and stem cell divisions, epiboly, separable instances of lineage dependent and position dependent fate determination, and epithelial interactions. The research proposed here would employ a variety of techniques, such as: the microinjectin of cell lineage tracers, photosensitizing dyes, drugs and radiochemicals; in situ hybridization; immunohistochemistry; gel electrophoresis; autoradiography; time lapse video recording; and low light fluorescence microscopy. From these studies, a more detailed description of various developmental processes and the mechanisms by which they operate should be generated. In addition, by examining a number of developmental processes in parallel in the same species, it is hoped that some understanding of the higher order mechanisms by which the basic cellular and developmental processes interact will emerge. For example, one part of this project would study the formation of specialized cytoplasmic domains prior to first cleavage and how they might influence the symmetry of the first cleavage. Another part would test the hypothesis that inherited RNAs regulate a change in cell division pattern. The question of how individual cells acquire their specific fates during early embryological development is a basic problem of developmental biology. Dr. Weisblat, using the leech as a model system, proposes a series of experiments to define what influences cell lineages of the embryo.