Cytokinesis and RNA segregation in zebrafish development

细胞质分裂是子细胞分裂的物理过程，对发育和生长调节具有重要意义。在许多情况下，细胞质分裂与细胞决定因子的不对称分离相结合，这反过来导致细胞类型的功能多样化。在对斑马鱼母系效应突变的系统鉴定中，鉴定出了两个突变，即aura和nebel基因，它们同时影响这两个过程。这些基因的突变由于细胞粘附和膜沉积缺陷而导致胚胎死亡。在这两种情况下，这种表型的基础是细胞质分裂完成的缺陷，可能是在卵裂面添加或稳定新膜。此外，这两种突变都影响vasa RNA分离途径的不同步骤，vasa RNA是赋予生殖细胞命运的特殊细胞质的组成部分。这两种类型的缺陷都可能是基于细胞骨架无法进行其功能所需的特定重排：在卵裂早期的多个阶段依赖于光环的微丝重排和形成沟时依赖于带的微管重组。本研究将确定这些基因在细胞质分裂和血管RNA分离过程中的确切作用。为此，我们将使用细胞生物学技术来可视化野生型和突变胚胎中的细胞成分，并通过抑制剂研究来确定亚细胞过程或网络的作用。此外，我们将通过定位克隆方法确定受影响基因的分子身份。对这些过程的理解将提供对各种知之甚少的主题的见解：i)完成细胞质分裂所涉及的过程，ii)分裂细胞内RNA和其他产物的不对称分离，以及iii)这两个过程所需的细胞机制之间的功能关系。

Cytokinesis, the physical process that divides daughter cells, is of fundamental importance to development and growth regulation. In many instances, cytokinesis is coupled with the asymmetric segregation of cellular determinants, which in turn results in the functional diversification of cell types. During the systematic identification of maternal-effect mutations in the zebrafish, two mutations, in the genes aura and nebel, were identified which affect both of these processes. Mutations in these genes result in embryonic lethality due to defects in cell adhesion and membrane deposition. In both cases, the basis of this phenotype is a defect in the completion of cytokinesis, possibly in the addition or stabilization of new membrane at the cleavage plane. In addition, both of these mutations affect different steps in a pathway of segregation of the vasa RNA, a component of a specialized cytoplasm that confers the germ cell fate. Both types of defects may be based on the inability of the cytoskeleton to undergo specific rearrangements required for its function: aura-dependent microfilament rearrangements at multiple stages during early cleavage and nebel-dependent microtubule reorganization at the forming furrow. The proposed research will determine the precise roles of these genes in the process of cytokinesis and the segregation of the vasa RNA. For this purpose we will use cell biological techniques to visualize cellular components in wild-type and mutant embryos and inhibitor studies to determine the role of subcellular processes or networks. In addition, we will determine the molecular identity of the affected genes through a positional cloning approach. The understanding of these processes will provide insights on a variety of poorly understood subjects: i) the processes involved in the completion of cytokinesis, ii) the asymmetric segregation of RNA and other products within dividing cells, and iii) the functional relationship between the cellular mechanisms required for these two processes.