Examining cytokinesis in reductive cell divisions

检查还原性细胞分裂中的胞质分裂

• 批准号: RGPIN-2021-03008
• 负责人: FitzHarris, Greg
• 金额: $ 4.23万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742329
• 关键词: Examining; cytokinesis; reductive; cell; divisions

Cytokinesis is the final stage of cell division, during which a single cell is divided into two daughter cells around the two sets of recently separated sister chromatids. The embryo is a spherical micro-organism that develops from a single cell into a ~100 cell blastocyst over the course of 4-5 days, during which time cells progressively halve in size with each cell division, and the first two cell lineages arise. It is thus a highly tractable system for examining aspects of cytokinesis in a complex multicellular context that are inaccessible in other mammalian systems. Here we will use live and fixed cell imaging approaches, genetic manipulations, and micro-manipulation, to perform the first mechanistic analysis of cytokinesis in the early mouse embryo. We will focus on separate two separate but inter-related sub-projects. First, we will determine whether furrowing speed is determined by cell size or cell differentiation. Our preliminary data suggests that, in stark contrast to C elegans where the speed of furrow ingression furrowing scales as a function of cell size, in mouse furrow ingression does not scale to cell size. We will use a variety of manipulations to test this notion thoroughly. Rather, we have found that furrowing speeds within the embryo diverge at the 16 cell stage, and have reason to believe this is attributable to one of several morphogenetic influences upon the outer cells at that stage, including changing cell shape, cell-cell adhesion, emergence of cellular polarity, and transcriptional-level cell fate decisions. We will explore furrow ingression during early development, and determine which of these developmental events impacts furrow ingression mechanisms. Second, we will determine the cause and consequence of abscission delay in dividing cells. We have confirmed a classic but unexplored observation that abscission is greatly delayed in the early mouse embryos, causing the formation of `cytoplasmic bridges' between sister cells through which large molecules can be shared. We will examine how these stable cytoplasmic bridges are formed, focussing on TEX14, the molecule responsible for the formation of stable bridges in germ cells, which we have found is also expressed in embryos. We will address the possibility that cytoplasmic bridges in the early embryo allow sister-cells to synchronise cell cycles, and thereby impact cell-division timing and cell-differentiation events. We expect to find that the early mouse embryo exists as a partial syncytium that serves to regulate early cell cycles and cell fate decisions. Overall, we expect this programme to establish the mouse embryo as a valuable model for the study of cytokinesis, and provide some of the very first information relating cytokinesis to cell size and lineage differentiation in a mammalian setting.

胞质分裂是细胞分裂的最后阶段，在此期间，单个细胞围绕两组最近分离的姐妹染色单体分裂成两个子细胞。胚胎是一个球形微生物，在4-5天的过程中从一个单细胞发育成一个约100个细胞的囊胚，在此期间，细胞随着每次细胞分裂而逐渐缩小一半，并出现前两个细胞谱系。因此，它是一个非常容易处理的系统，用于检查在复杂的多细胞背景下，在其他哺乳动物系统中无法访问的胞质分裂方面。在这里，我们将使用活细胞和固定细胞成像方法，遗传操作和显微操作，在早期小鼠胚胎中进行胞质分裂的第一个机制分析。我们将侧重于两个独立但相互关联的子项目。首先，我们将确定开沟速度是否由细胞大小或细胞分化决定。我们的初步数据表明，在形成鲜明对比的秀丽隐杆线虫中，沟内陷开沟的速度是细胞大小的函数，在小鼠中，沟内陷不与细胞大小成比例。我们将使用各种操作来彻底测试这个概念。相反，我们已经发现，在16细胞阶段，胚胎内的开沟速度出现分歧，并有理由相信这是由于在该阶段对外部细胞的几种形态发生影响之一，包括改变细胞形状，细胞-细胞粘附，细胞极性的出现，以及转录水平的细胞命运决定。我们将探讨在早期发展的沟内陷，并确定这些发展事件的影响沟内陷机制。第二，我们将确定分裂细胞中分裂延迟的原因和后果。我们已经证实了一个经典但未经探索的观察结果，即在早期小鼠胚胎中，细胞分裂大大延迟，导致姐妹细胞之间形成“细胞质桥”，通过这种桥可以共享大分子。我们将研究这些稳定的细胞质桥是如何形成的，重点是TEX 14，这是一种负责在生殖细胞中形成稳定桥的分子，我们发现它也在胚胎中表达。我们将讨论早期胚胎中的细胞质桥允许姐妹细胞同步细胞周期的可能性，从而影响细胞分裂时间和细胞分化事件。我们期望发现早期小鼠胚胎作为部分合胞体存在，其用于调节早期细胞周期和细胞命运决定。总体而言，我们希望这个计划建立小鼠胚胎作为一个有价值的模型，胞质分裂的研究，并提供了一些非常第一的信息有关胞质分裂细胞的大小和谱系分化在哺乳动物的设置。