Cell type-variation of cytokinesis

项目概述：在动物细胞中，胞质分裂是由肌动蛋白收缩环的收缩驱动的， 它的定位和控制由纺锤体微管发出的信号控制。长期以来，人们一直认为所有的 动物细胞通过类似的分子机制进行分裂。然而，胞质分裂的变异，或机制的多样性 对于多细胞生物体内不同类型的细胞，调控途径正变得越来越清晰。 这种细胞类型特异性调节胞质分裂的机制仍然知之甚少。在……里面 初步研究，我们建立了线虫4-细胞胚胎作为研究细胞类型特异性的系统 胞质分裂的调节。在4细胞阶段，每个单独的细胞已经有了唯一的细胞命运，由 保守的细胞命运信号通路(例如，Src、Wnt/Frizzleed、Notch/Delta)并依赖于直接细胞-细胞 胚胎内特定细胞对之间的接触。使用化学物质(LatrunculinA)或遗传物质(形成 温度敏感突变体)的扰动削弱了F-肌动蛋白收缩环，我们鉴定了细胞类型- 4-细胞胚胎胞质分裂的特异性调节。我们发现四个细胞中有两个受到更多的保护 而当F-肌动蛋白细胞骨架被 被削弱了。胚胎显微解剖和细胞配对实验显示，在这两种保护中的一种 细胞(P2)，细胞动力学保护是细胞固有的，取决于生殖系命运的规范，而在 其他受保护的细胞(EMS)，细胞运动保护是细胞外在调节的，需要直接的细胞-细胞 与其相邻细胞(P2)的接触和依赖于Src的细胞命运信号。利用我们收集的ts突变体，我们 还确定了针对纺锤体信号受损时细胞质分裂失败的特定细胞类型的保护 在4-细胞和8-细胞胚胎中都有机械。这个方案中的实验将确定分子 细胞命运规范通过三种方式调节细胞质分裂中特定细胞类型的变异的机制： 1)我们将确定依赖细胞命运的细胞动力学背后的细胞和分子机制。 基于肌动蛋白的损伤后的保护；2)我们将比较针对细胞质分裂的细胞类型特异性保护 纺锤体信号传递后的失败-肌动蛋白损伤后的损伤-4-到16-细胞胚胎中的损伤和鉴定 保守的和细胞类型特定的机制，保护不同的细胞动力学压力；以及3)我们将 在多细胞的情况下，确定细胞命运的规定是否也可以保护胞质分裂免受压力 组织，以及测试适用于早期胚胎的原理是否也适用于 文化。计划中的实验将确定细胞命运信号在促进基因变异中的作用。 胞质分裂，确定特定的细胞命运途径并测试其作用机制，并确定 胞质分裂中细胞类型特异性变异的普遍性。因为胞质分裂失败和细胞周期调节失调 细胞命运信号既是人类疾病(如癌症)的生物标志物，又受 由于进化上保守的分子机制，我们的工作将与人类健康相关。

PROJECT SUMMARY: In animal cells, cytokinesis is driven by constriction of an actomyosin contractile ring, which is positioned and controlled by signaling from spindle microtubules. It has long been assumed that all animal cells divide by a similar molecular mechanism. Yet variation in cytokinesis, or diversity in mechanistic and regulatory pathways, is becoming increasingly clear for different cell types within multicellular organisms. The mechanisms underlying this cell type-specific regulation of cytokinesis remain poorly understood. In preliminary studies, we established the C. elegans 4-cell embryo as a system to study cell type-specific regulation of cytokinesis. At the 4-cell stage, each individual cell already has a unique cell fate, specified by conserved cell fate signaling pathways (e.g. Src, Wnt/frizzled, Notch/Delta) and dependent on direct cell-cell contact between specific cell pairs within the embryo. Using either chemical (LatrunculinA) or genetic (formin temperature sensitive mutant) perturbations to weaken the F-actin contractile ring, we identified cell type- specific regulation of cytokinesis in the 4-cell embryo. We found that two of the four cells are more protected against cytokinetic stress than the others and can divide successfully when the F-actin cytoskeleton is weakened. Embryo micro-dissection and cell pairing experiments revealed that in one of these two protected cells (P2), cytokinetic protection is cell-intrinsic and dependent on germline fate specification, whereas in the other protected cell (EMS), cytokinetic protection is cell-extrinsically regulated and requires direct cell-cell contact with its neighbor cell (P2) and Src-dependent cell-fate signaling. Using our collection of ts mutants, we also identified cell type-specific protection against cytokinesis failure upon damage to the spindle signaling machinery in both the 4- and 8-cell embryo. The experiments in this proposal will determine the molecular mechanisms by which cell fate specification regulates cell type-specific variation in cytokinesis in three ways: 1) we will identify the cellular and molecular mechanisms that underlie cell fate-dependent cytokinetic protection after actin-based damage; 2) we will compare the cell type-specific protection against cytokinesis failure after spindle signaling-damage to that after actin-damage in the 4- thru 16-cell embryo and identify conserved and cell type-specific mechanisms that protect against different cytokinetic stresses; and 3) we will determine if cell fate specification can also protect cytokinesis from stress in the context of a multicellular tissue, as well as test whether the principles that apply to the early embryo also apply to mammalian cells in culture. The proposed experiments will define the role of cell fate signaling in promoting variation in cytokinesis, identify specific cell fate pathways and test their mechanisms of action, and determine the universality of cell type-specific variation in cytokinesis. Because both cytokinesis failure and dysregulation of cell fate signaling are both emerging as biomarkers for human diseases such as cancer and are regulated by evolutionarily conserved molecular mechanisms, our work will have relevance for human health.