Asynchronous mitosis in multinucleate cells

描述(申请人提供)：在从单细胞酵母到哺乳动物的各种生物体中，即使在相同的环境中生长，基因相同的细胞也表现出不同的细胞分裂周期。在一个过程中，比如细胞周期的准确性，可变性的来源和好处是未知的。特别是，人们不知道细胞周期时序的可变性是否纯粹是随机的，或者它是否可以作为细胞周期电路设计的一部分进行调节。其他细胞过程中的可变性已被证明是有益的，因此细胞周期可变性实际上可能是一种适应性特征。多核的丝状真菌Ashbya Cotsypii是研究细胞周期时序变异性的独特模型系统，因为细胞核在共同的细胞质内异步分裂。合胞体中的这种异步性需要细胞周期信号的可变时序和核自主。由于所有的蛋白质都是在一个共同的细胞质中翻译的，所以神秘的是，多个不同步的细胞周期振荡器可以共存。我们正在利用这个模型系统中的异步分裂周期来发现可变性是否被编程到细胞周期中，并了解如何建立核自主性。对变异的分子基础的了解对于全面了解细胞周期控制和细胞周期调控不当所影响的病理是必要的。细胞周期决定的种群水平的变异性可以影响多种过程，如真菌发病机制和肿瘤细胞行为，并可能是影响药物治疗效果的一个因素。虽然一些细胞间的可变性可以归因于转录过程中的分子噪音，但可以肯定的是，还有其他尚未确定的非遗传个体的细胞储存库存在。在这项建议中，我们将活细胞成像与计算和分子遗传学方法相结合，以确定细胞周期中的可变性来源，并确定核自主性是如何建立的。有了这个模型真菌系统，我们可以很好地识别细胞周期可变性的保守来源，并了解如何在共同的细胞质中隔离细胞信号过程。该项目的具体目标是：1)确定G1持续时间的变异性是随机的还是有规律的。2)检验核大小控制细胞周期时序和变异性的假设。3)检验空间受限的蛋白质运动产生核自主性的假设。时间可变性几乎存在于所有的细胞分裂周期中，了解异质性的基础对于全面理解细胞周期至关重要。在这个项目中，我们将确定细胞分裂周期中是否存在时序可变性，了解核大小如何控制时序，以及细胞质如何在功能上划分以保持异步性。 与公共卫生相关：在从单细胞酵母到哺乳动物的各种生物中，即使在相同的环境中生长，基因相同的细胞也需要不同的时间才能分裂。这种细胞间的分裂时间变异可以影响真菌发病机制和肿瘤细胞生长等不同的过程，并可能是影响药物治疗效果的一个因素。在这项工作中，我们将确定与细胞分裂周期失控影响的各种疾病相关的时间变异性的分子来源。

DESCRIPTION (provided by applicant): In organisms ranging from single-celled yeasts to mammals, genetically identical cells exhibit variable cell division cycle times even when growing in the same environment. The sources and benefits of variability in a process such as the cell cycle that is wired for accuracy are unknown. In particular, it is not understood whether cell cycle timing variability is purely stochastic or whether it may be regulated as part of the design of cell cycle circuits. Variability in other cell processes has been shown to be beneficial, so cell cycle variability may in fact be an adaptive trait. The multinucleate, filamentous fungus, Ashbya gossypii, is a unique model system to study cell cycle timing variability because nuclei divide asynchronously within a common cytoplasm. Such asynchrony in a syncytium requires variable timing and nuclear autonomy in cell cycle signaling. As all proteins are translated in a common cytoplasm, it is mysterious how multiple, out of sync, cell cycle oscillators can coexist. We are taking advantage of the asynchronous division cycle in this model system to discover whether variability is programmed into the cell cycle and to learn how nuclear autonomy can be established. Knowledge of the molecular basis for variability is necessary for a complete understanding of cell cycle control and the pathologies influenced by a misregulated cell cycle. Population level variability in cell cycle decisions can impact processes as diverse as fungal pathogenesis and tumor cell behavior, and may be a factor influencing the efficacy of pharmacological treatments. While some cell-to-cell variability can be attributed to molecular noise in transcription, it is certain that other, as yet unidentified, cellular reservoirs of non-genetic individuality exist. In this proposal, we combine live cell imaging with computational and molecular genetic approaches to identify sources of variability in the cell cycle and determine how nuclear autonomy is established. With this model fungal system, we are well positioned to identify conserved sources of cell cycle variability and learn how cell signaling processes can be insulated within a common cytoplasm. The specific aims of the project are: 1) To determine whether variability in G1 duration is stochastic or regulated. 2) To test the hypothesis that nuclear size controls cell cycle timing and variability. 3) To test the hypothesis that spatially restricted protein movement creates nuclear autonomy. Timing variability exists in nearly all cell division cycles and knowing the basis of heterogeneity is essential for a complete understanding of the cell cycle. In this project, we will determine if timing variability is programmed in the cell division cycle, learn how nuclear size controls timing and how the cytoplasm can be functionally compartmentalized to maintain asynchrony. PUBLIC HEALTH RELEVANCE: In organisms ranging from single-celled yeasts to mammals, genetically identical cells take different amounts of time to divide even when growing in the same environment. This cell-to-cell variability in division timing can impact processes as diverse as fungal pathogenesis and tumor cell growth, and may be a factor influencing the efficacy of pharmacological treatments. In this work we will identify molecular sources of timing variability that will have relevance to the diverse diseases influenced by a misregulated cell division cycle.