Molecular basis of cell cycle timers and their coordination during organogenesis

大多数动物物种开始生命时都是一个单细胞受精卵重复细胞分裂形成它们的身体。在细胞增殖过程中，细胞分裂时间的编排对于组织和器官的形成和维持至关重要。虽然细胞分裂的激活剂和抑制剂是已知的，但在多细胞系统中精确指定细胞分裂时间的分子机制仍然是一个谜。在我们的身体中，单个细胞接收不同的物理和化学信息。这样的组织复杂性是多细胞生物体中细胞分裂研究的实质性负担。事实上，多细胞研究往往最终发现相关性，而不是因果关系。为了克服这个问题，我们将使用一个独特的系统，这将有效地帮助我们理解多细胞分裂的复杂性。我们的系统有四个优点-第一，选择的模式生物，线虫C。elegans只有959个体细胞，但足够复杂，可以形成不同的组织和器官;第二，在C.第三，细胞分裂的时间和方向在个体蠕虫之间是不变的;这个特征提供了一个很大的优势，可以精确地理解单细胞分辨率下多细胞分裂的调节;最后，我们最近开发了一种重建和简化多细胞环境的方法，使用分离的胚胎细胞和人工珠，这将为我们理解多细胞环境和细胞分裂时间之间的因果关系提供前所未有的优势。通过利用我们独特的系统，我们将解决以下问题：Q1：指定细胞分裂时间的分子计时器是什么？Q2：在器官形成过程中，细胞分裂的时间是如何协调的？预计细胞分裂时机的协调在功能性多细胞组装体（如器官）的发育中更为关键。我们将使用C。elegans肠作为模型器官。梭线虫的肠仅由20个细胞组成，这些细胞起源于称为“E”的单个前体细胞，其后代在不同的时间分裂。我们将：1）精确测量不同细胞类型中核心细胞分裂调节因子的活性; 2）识别特定细胞类型所需的分裂时间调节剂; 3）通过整合多细胞重建测定，遗传学和实时成像，揭示环境信号和细胞分裂时间之间的因果关系。从蠕虫到人类，各种动物的细胞分裂调节因子都非常相似。因此，我们的研究使用C.线虫应该揭示协调多细胞分裂和动物发育的关键机制。

Most animal species begin life as a single cell-a fertilized egg that repeats cell divisions to form their body. In the course of cell proliferation, the orchestration of cell division timings is critical for the formation and maintenance of tissues and organs. Although activators and inhibitors of cell division are known, the molecular mechanisms that precisely specify cell division timing remains a mystery in multicellular system. In our body, individual cells receive different physical and chemical information. Such tissue complexity is a substantial burden for cell division studies in multicellular organisms. Indeed, multicellular studies often end up finding correlation rather than causation. To overcome this problem, we will use a unique system that will efficiently and effectively help us understand the complexity of multicellular division. Our system has four strengths - first, the chosen model organism, the nematode C. elegans, has only 959 somatic cells, but is complex enough to form different tissues and organs; second, a number of genetic tools are available in C. elegans, thereby allowing us to search cell division regulators out of all ~20,000 genes of this animal; third, the timing and orientation of cell division are invariant among individual worms; this feature offers a great advantage to precisely understand the regulation of multicellular division at single-cell resolution; finally, we have recently developed a method to reconstitute and simplify the multicellular environment, using isolated embryonic cells and artificial beads, which will afford us an unprecedented advantage to understand the causal relationship between the multicellular environment and the timing of cell division. By taking advantages of our unique system, we will address the following questions: Q1: What are the molecular timers that specify cell division timing? Q2: How are cell division timings coordinated during organ formation? It is expected that the coordination of cell division timing is more critical in the development of functional multicellular assembly, such as organs. We will use the C. elegans intestine as a model organ. The C. elegans intestine is composed of only 20 cells originating from a single precursor cell called "E", the descendants of which divide at different times. We will - 1) precisely measure the activities of core cell division regulators in different cell types; 2) identify division timing modifiers required in specific cell types; 3) reveal a causal relationship between environmental signal and cell division timing by integrating multicellular-reconstitution assays, genetics, and live-imaging. Cell division regulators are remarkably similar among animals from worms to humans. Thus, our study using C. elegans should uncover the critical mechanisms that orchestrate multicellular division and animal development.