Mechanisms of mitosis and size control in Xenopus

非洲爪蟾有丝分裂和大小控制的机制

• 批准号: 10589896
• 负责人: Rebecca W Heald
• 金额: $ 87.01万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-12 至 2026-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10589896
• 关键词: Address; Affect; Architecture; Area; Automobile Driving; Biochemical; Biological; Biological Assay; Biology; Biophysical Process; Cell Nucleus; Cell Size; Cell division; Cell physiology; Cells; Centromere; Chromosome Condensation; Chromosome Segregation; Chromosomes; Ciona intestinalis; Collaborations; Computer Models; Cytoplasm; Cytoskeleton; DNA; Defect; Development; Embryo; Embryonic Development; Ensure; Event; Evolution; Gene Expression; Genome; Genomics; Hybrids; Interphase; Kinetochores; Laboratories; Life; Link; Malignant Neoplasms; Measures; Mediating; Meiosis; Microfluidics; Microscopy; Microtubules; Mitosis; Mitotic; Mitotic Chromosome; Mitotic spindle; Molecular; Morphology; Oocytes; Organelles; Organism; Phylogenetic Analysis; Physiology; Ploidies; Process; Productivity; Proteomics; Rana; Research; Resolution; Role; Shapes; Structure; Surface; System; Techniques; Testing; Time; Urochordata; Xenopus; cell type; chromosome missegregation; chromosome replication; daughter cell; egg; embryo cell; human disease; in vivo; innovation; insight; laser tweezer; novel; novel strategies; optic tweezer; reproductive; segregation; sensor; single molecule; sperm cell; virtual; xenopus development

PROJECT SUMMARY Mechanisms of Mitosis and Size Control in Xenopus Research in my laboratory is focused on two major areas: Cell division is arguably the most dramatic event in the life of a cell. Chromosomes condense, organelles vesiculate, and the microtubule cytoskeleton rearranges into a bipolar spindle that attaches to chromosomes at their kinetochores and segregates a complete genome to each daughter cell. Although the morphological changes that occur during mitosis were first observed over a century ago, we still do not understand how these dynamic events are orchestrated. Many factors have been identified that contribute to spindle assembly and function, but the molecular and biophysical mechanisms and interactions that ensure mitotic fidelity remain unclear. Our current projects address outstanding questions including 1) What are the molecular underpinnings and functional consequences of different spindle architectures? Spindle size and organization vary dramatically across cell types and organisms, and factors known to affect these parameters are altered in many cancers, but how specific spindle features are established and their effects on chromosome segregation and cell division are poorly understood. We will leverage morphometric and phylogenetic comparisons together with biochemical and functional assays to investigate the dramatic changes in spindle architecture that occur between oocyte meiosis and the mitotic divisions of early development in Xenopus and the sea squirt Ciona intestinalis. We will elucidate the role of specific factors in this transition, and examine the consequences of altering spindle architecture on embryo cell division. 2) What defects in cell division mechanisms underlie speciation? We have observed chromosome mis-segregation in inviable hybrids generated by fertilizing Xenopus tropicalis eggs with X. laevis sperm, and identified incompatibility between a subset of paternal centromeres and maternal cytoplasm as one underlying cause. We will elucidate the molecular basis of inter-species conflicts that impact cell division and contribute to reproductive isolation. 3) What is the molecular basis of mitotic chromosome condensation? We have developed a novel approach using optical tweezers to measure the dynamics of single DNA molecules in real-time in Xenopus egg extracts with high spatial and temporal precision and will use this system to dissect the roles of key factors in driving mitotic chromosome assembly. Absolute and relative size of biological entities varies widely, both within and among species at all levels of organization above the atomic/molecular: the organism, the cells that make up the organism, and the cellular components. How does scaling occur so that everything fits and functions properly? Correct scaling inside cells is crucial for cell function, architecture, and division, but until recently the control systems that a cell uses to regulate the size of its internal structures were virtually unknown. We have established assays to elucidate mechanisms of intracellular scaling between different-sized frog species and during the rapid, reductive cell divisions of early embryogenesis. We are further developing these systems to ask: 1) What scales mitotic chromosome size to cell size? We are testing the hypothesis that a surface area to volume sensor acting on the interphase nucleus and the mitotic spindle also coordinately adjusts mitotic chromosomes to cell size during Xenopus development. 2) What are the connections between genome size, cell size, physiology, and development? Cell size correlates strongly with genome size across evolution, but underlying mechanisms are unknown. We will utilize different ploidy frog embryos to address how altering genome size affects gene expression, and a variety of species including the dodecaploid frog Xenopus longipes to investigate relationships between genome size, cell division mechanisms, development, and physiology. The means to address these fundamental cell biological questions is enabled by powerful experimental systems based on cytoplasmic extracts and functional in vivo assays in vertebrate (Xenopus) embryos. We have established productive collaborations and apply diverse techniques including high-resolution microscopy, single molecule assays, genomics, proteomics, microfluidics and computational modeling to fill important conceptual gaps in an innovative, rigorous, and interdisciplinary manner. Our research will continue to provide novel insight into cell division and size control, processes essential for viability and development, and defective in human diseases including cancer. Although introduced as distinct topics, cell division and size control are intimately linked. We are increasingly focused on how cross-species comparisons can elucidate molecular mechanisms underlying cell division and size control, as well as how biological constraints related to these processes have shaped evolution. Together, these projects uniquely advance our understanding of long-standing questions in biology.

项目总结 非洲爪哇有丝分裂和大小控制的机制 我实验室的研究主要集中在两个主要领域： 细胞分裂可以说是细胞生命中最戏剧性的事件。染色体浓缩，细胞器 微管细胞骨架重新排列成两极纺锤体，该纺锤体附着在染色体上 它们的动粒连接并将完整的基因组分离到每个子细胞。虽然形态上的 在有丝分裂过程中发生的变化是在一个多世纪前首次观察到的，我们至今仍不清楚 这些动态事件是如何编排的。已经确定了导致纺锤体的许多因素 组装和功能，但确保有丝分裂的分子和生物物理机制和相互作用 富达目前仍不清楚。我们目前的项目正在解决悬而未决的问题，包括1)什么是分子 不同主轴架构的基础和功能后果？磁盘轴大小和组织 不同细胞类型和生物体的差异很大，已知的影响这些参数的因素在 许多癌症，但如何建立特定的纺锤体特征及其对染色体分离的影响 以及细胞分裂对此知之甚少。我们将一起利用形态计量学和系统发育比较 通过生化和功能分析来研究纺锤体结构发生的戏剧性变化 非洲爪哇和海鞘卵母细胞减数分裂与早期发育有丝分裂的关系 肠肌。我们将阐明特定因素在这一过渡中的作用，并研究 改变胚胎细胞分裂的纺锤体结构。2)细胞分裂机制的缺陷是什么 物种形成？我们观察到了非洲爪哇受精产生的无效杂交后代的染色体错误分离。 热带虫卵与莱维氏X.laevis精子之间的亲和性，并鉴定出父系着丝粒的子集与 母体细胞质是一个潜在的原因。我们将阐明物种间冲突的分子基础 影响细胞分裂并有助于生殖隔离。3)有丝分裂染色体的分子基础是什么 冷凝？我们开发了一种新的方法，利用光镊子来测量单个分子的动力学。 非洲爪哇卵提取的实时DNA分子具有高空间和时间精度，并将使用这一技术 系统剖析了驱动有丝分裂染色体组装的关键因素的作用。 生物实体的绝对和相对大小差异很大，无论是在物种内部还是在物种之间 原子/分子之上的组织：有机体、构成有机体的细胞和细胞 组件。如何进行伸缩，以使一切都适合并正常运行？正确调整内部比例 细胞对细胞的功能、结构和分裂至关重要，但直到最近， 细胞用来调节其内部结构的大小几乎是未知的。我们已经建立了检测方法 为了阐明不同大小青蛙物种之间细胞内结垢的机制以及在快速、 早期胚胎发育过程中细胞分裂减少。我们正在进一步开发这些系统，以问：1)规模是多少 有丝分裂染色体大小与细胞大小之比？我们正在测试一种假设，即表面积与体积传感器之间的相互作用 在间期核和有丝分裂纺锤体上也协调地调整有丝分裂染色体以适应细胞大小 在非洲爪哇发展过程中。2)基因组大小、细胞大小、生理和 发展？细胞大小与进化过程中的基因组大小密切相关，但潜在的机制是 未知。我们将利用不同倍性的青蛙胚胎来研究基因组大小的改变如何影响基因 表达，并与包括十二倍体长爪爪蛙在内的各种物种进行关系调查 基因组大小、细胞分裂机制、发育和生理之间的关系。 解决这些基本细胞生物学问题的手段是由强大的实验系统实现的 基于细胞质提取物和脊椎动物(非洲爪哇)胚胎的体内功能分析。我们有 建立了富有成效的合作并应用了各种技术，包括高分辨率显微镜、单一 分子分析、基因组学、蛋白质组学、微流体学和计算模型来填补重要的概念 以创新、严谨和跨学科的方式发现差距。我们的研究将继续提供新的见解 到细胞分裂和大小控制，对生存和发育至关重要的过程，在人类中是有缺陷的 包括癌症在内的疾病。虽然作为不同的主题介绍，但细胞分裂和大小控制是密切相关的 已链接。我们越来越关注如何通过跨物种比较来阐明分子机制 潜在的细胞分裂和大小控制，以及与这些过程相关的生物限制如何 塑造了进化。这些项目共同推动了我们对长期存在的问题的理解 生物学。