Trigger waves and coupled oscillations in the embryonic cell cycle

胚胎细胞周期中的触发波和耦合振荡

• 批准号: 9212155
• 负责人: JAMES E. FERRELL
• 金额: $ 31.98万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-02-15 至 2019-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9212155
• 关键词: Action Potentials; Animals; Apoptosis; Apoptotic; Attention; Axon; Behavior; Biochemistry; Biological Models; Biological Process; Calcium Oscillations; Caliber; Cardiovascular system; Caspase; Cell Cycle; Cell Death; Cell Nucleus; Cells; Centrosome; Communication; Complex; Congresses; Coupled; Coupling; Cyclic AMP; Cytoplasm; Development; Diffuse; Diffusion; Elements; Embryo; Ensure; Event; Evolution; Feedback; Fluorescence Microscopy; Gap Junctions; Generations; Hour; Individual; Meiosis; Mitosis; Mitotic; Modeling; Nature; Neurons; Oocytes; Phase; Physarum polycephalum; Process; Property; Protein Phosphatase 2A Regulatory Subunit PR53; Proteins; Publishing; Regulation; Role; Side; Speed; Stimulus; Surface; System; Teflon; Temperature; Testing; Time; Tissues; Tube; Walking; Work; Xenopus; Xenopus laevis; blastomere structure; cell cortex; cytochrome c; egg; embryo stage 2; experimental study; public health relevance; zygote

DESCRIPTION (provided by applicant): Recently we demonstrated that the bistability of the Cdk1/Cdc25/Wee1 system allows Cdk1 activation to propagate rapidly through Xenopus cytoplasm by means of what are termed trigger waves, waves of activation and inactivation that spread the way action potentials spread down an axon. This work was made possible through the development of a Teflon tube system that is compatible with fluorescence microscopy and allows cycling extracts to carry out a dozen or more complete cell cycles without dying. The speed of the Cdk1 trigger wave (~60 �m/min) is sufficient to account for the dynamics of mitosis and of the surface contraction waves (SCWs) that occur prior to cleavage in intact embryos. This work was published last year in Nature. We propose to build upon this work through studies divided into three Specific Aims: Aim 1. Mitotic and meiotic trigger waves in eggs, oocytes, and extracts. We now plan to examine mitotic waves in greater spatial detail and examine the roles of nuclei and centrosomes in the generation and propagation of these waves. We also plan to examine the interplay between mitotic waves, which we suspect helps keep ectopic foci of Cdk1 activation from disorganizing the first cell cycle. Finally, we plan to characterize the mechanism and significance of a newly discovered meiotic trigger wave phenomenon in oocytes, which we suspect may be involved in the expulsion of the first polar body and the completion of meiosis 1. Aim 2. Intercellular coupling and the synchronization of multicellular embryos. Once the fertilized egg begins to divide, the issue of keeping mitosis spatially coordinated within individual blastomeres becomes less problematic, but the issue of keeping mitosis coordinated between separate cells becomes more problematic. In preliminary studies we have shown that when an embryo is desynchronized with a transitory temperature gradient, the cells subsequently return toward synchrony. Several mechanisms, singly or together, may explain this synchronization, including communication through cytoplasmic bridges, gap junctions, and cytoskeletal elements. We plan to test these ideas through experiments in intact embryos and egg extracts. Aim 3. Spatial coordination of apoptosis. The caspase system includes multiple positive feedback loops that could generate bistability and help ensure that apoptosis is all-or-none and irreversible in character. We plan to test whether caspase activation is, in fact, bistable, using Xenopus egg extracts as a model system. If it is, then it is possible that this bistability allows the apoptotic state to propagate rapidly through te egg via trigger waves. Preliminary studies indicate that this is the case: the apoptotic state apparently propagates through Xenopus cytoplasm at a constant speed of ~15 �m/min. We plan to characterize these waves in the Teflon tube extract system and to dissect the feedback loops that generate them.

描述（由申请人提供）：最近，我们证明了Cdk1/Cdc25/Wee1系统的双稳定性允许Cdk1激活通过爪蟾细胞质快速传播，通过所谓的触发波，激活和失活波传播动作电位沿轴突传播的方式。这项工作是通过开发一种与荧光显微镜兼容的聚四氟乙烯管系统实现的，该系统允许循环提取物在不死亡的情况下进行十几个或更多的完整细胞周期。Cdk1触发波的速度（~60 μ m/min）足以解释完整胚胎有丝分裂和表面收缩波（SCWs）发生在卵裂之前的动力学。这项研究去年发表在《自然》杂志上。我们建议在这项工作的基础上，通过分为三个具体目标的研究：目标1。卵、卵母细胞和提取液中的有丝分裂和减数分裂触发波。我们现在计划在更大的空间细节上研究有丝分裂波，并研究核和中心体在这些波的产生和传播中的作用。我们还计划研究有丝分裂波之间的相互作用，我们怀疑这有助于防止Cdk1激活的异位灶在第一个细胞周期中紊乱。最后，我们计划描述一种新发现的卵母细胞减数分裂触发波现象的机制和意义，我们怀疑这可能参与了第一极体的排出和减数分裂1的完成。目标2。细胞间偶联与多细胞胚胎的同步。一旦受精卵开始分裂，保持单个卵裂球内有丝分裂空间协调的问题就变得不那么成问题了，但保持独立细胞间有丝分裂协调的问题就变得更成问题了。在初步的研究中，我们已经表明，当胚胎与短暂的温度梯度去同步时，细胞随后又回到同步。有几种机制可以单独或共同解释这种同步，包括通过细胞质桥、间隙连接和细胞骨架元件进行通信。我们计划通过完整胚胎和卵子提取物的实验来验证这些想法。目标3。细胞凋亡的空间协调。caspase系统包括多个正反馈回路，可以产生双稳定性，并有助于确保细胞凋亡是全或无和不可逆的。我们计划测试半胱天冬酶的激活是否实际上是双稳态的，使用爪蟾卵提取物作为模型系统。如果是这样，那么这种双稳定性可能允许凋亡状态通过触发波在卵子中快速传播。初步研究表明：凋亡状态明显以~15 μ m/min的恒定速度在爪蟾细胞质中传播。我们计划在聚四氟乙烯管提取系统中表征这些波，并剖析产生它们的反馈回路。