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Cdk 1/Cdc 25/Wee 1系统的双稳态允许Cdk 1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而实现的，该系统允许循环提取物进行十几个或更多个完整的细胞周期而不死亡。Cdk 1触发波的速度（~60 μ m/min）足以解释完整胚胎中有丝分裂和卵裂前发生的表面收缩波（SCW）的动力学。这项工作去年发表在《自然》杂志上。我们建议通过分为三个具体目标的研究来加强这项工作：目标1。卵、卵母细胞和提取物中的有丝分裂和减数分裂触发波。我们现在计划研究有丝分裂波在更大的空间细节，并检查这些波的产生和传播的核和中心体的作用。我们还计划研究有丝分裂波之间的相互作用，我们怀疑这有助于保持异位病灶的Cdk 1激活扰乱第一个细胞周期。最后，我们计划描述新发现的卵母细胞减数分裂触发波现象的机制和意义，我们怀疑它可能参与第一极体的排出和减数分裂1的完成。目标2.细胞间偶联和多细胞胚胎的同步化。一旦受精卵开始分裂，在单个卵裂球内保持有丝分裂空间协调的问题就变得不那么成问题了，但是在单独的细胞之间保持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，当胚胎在短暂的温度梯度下去分化时，细胞随后会恢复同步。几种机制，单独或一起，可以解释这种同步，包括通过细胞质桥，缝隙连接，和细胞骨架元素的通信。我们计划通过完整胚胎和卵子提取物的实验来测试这些想法。目标3.凋亡的空间协调。半胱天冬酶系统包括多个正反馈环，可以产生双稳态，并有助于确保细胞凋亡是全或无和不可逆的。我们计划使用非洲爪蟾卵提取物作为模型系统来测试半胱天冬酶激活是否实际上是激活的。如果是这样，那么这种双稳态可能允许凋亡状态通过触发波快速传播到卵细胞。初步研究表明，情况就是这样：凋亡状态显然以~15 μ m/min的恒定速度在非洲爪蟾细胞质中传播。我们计划在特氟龙管提取系统中描述这些波的特征，并解剖产生它们的反馈回路。