Mps1 and regulation of kinetochore-microtubule interactions in meiosis

在细胞内准确移动染色体的能力对生物体的生存至关重要。成功的细胞分裂首先取决于复制每条染色体中包含的遗传物质，然后积极地将染色体分成两组，最后分裂细胞，使每个子细胞只包含两组染色体中的一组。有性生殖的生物体有两种类型的细胞分裂，有丝分裂和减数分裂。有丝分裂产生大多数细胞类型，而减数分裂产生配子。在这两种类型的分裂中，染色体的运动都是通过将称为微管的电缆连接到染色体上称为着丝点的连接点上，然后缩短电缆将染色体拉到目的地来实现的。这些电缆从细胞核的两侧形成两个阵列。为了连接到电缆末端，复制的染色体必须首先向细胞核的中间移动。两种类型的染色体分离事件，有丝分裂和减数分裂，有一些相似之处，但它们的一些差异的分子基础尚不清楚。Mps1是一种保守蛋白，在有丝分裂和减数分裂中都是必需的，但具有减数分裂特异性功能，可能揭示了这些过程的根本差异。本项目旨在区分Mps1在有丝分裂和减数分裂中的不同作用和分子机制。Mps1定位于着丝点，可能通过激活其他蛋白质来控制染色体的运动，使染色体移动到微管阵列的中间，连接到微管末端，缩短微管以移动染色体。这个项目将有一个更广泛的影响，为俄克拉何马州的高中和大学生提供一个机会来执行独立的假设驱动的基础研究项目。来自当地城市高中的学生将有机会进行为期一年的研究项目，他们将研究可能与Mps1相互作用以控制染色体运动的候选蛋白质。每年夏天，在一个住宅研究项目中，两名来自俄克拉何马州农村地区的学生将能够参加为期八周的研究实习，研究Mps1控制染色体运动的机制。这个项目的综合目标是促进对复杂细胞过程的理解，并向学生介绍基础研究的文化。有丝分裂或减数分裂纺锤体上染色体的准确分离取决于一系列连续的步骤。第一批染色体向纺锤体中央区移动，这一步骤被称为染色体聚集。第二种正确的着丝点-微管（k-MT）连接形成。然后着丝点微管解聚，促进染色体向两极迁移。但是触发这些事件的信号是什么呢？MPS1编码一种保守的必需激酶，该激酶已被证明参与细胞周期进程的几个关键步骤，并在几种生物的有丝分裂和减数分裂中参与染色体分离。来自分裂酵母和哺乳动物的实验表明，Mps1促进染色体滑行，这是一个在早期中期染色体向纺锤体中央区移动的过程。此外，在出芽酵母减数分裂中，Mps1需要形成稳定的k-MT附着体，然后需要触发MT解聚以促进染色体向极地运动。该项目验证了Mps1是芽殖酵母减数分裂中染色体分离多个序列事件的关键调节因子的假设。该项目将阐明驱动有序减数分裂染色体行为的新机制。这个项目有三个目标。首先是确定Mps1的几个功能在减数分裂中是否保守，包括mt依赖的染色体从极向纺锤体中间区滑动，称为染色体滑动。这一目标也将检验Mps1是调节这一过程所必需的假设，并确定其调节目标。第二个目标是确定Mps1的几个蛋白磷酸化靶点在双向过程的三个连续步骤中的作用：在早期中期进入纺锤体中间区，着丝点附着到mt上，以及着丝点mt的解聚以触发极向染色体运动。第三个目标是利用MPS1的一个功能分离等位基因（MPS1 - r170s），它表现出非常轻微的有丝分裂缺陷，但严重的减数分裂缺陷。在mps1-R170S突变体中已经分离到改善减数分裂染色体分离的抑制突变。这些突变体将被评估以确定减数分裂中对Mps1功能异常敏感的途径。总之，这些实验将阐明Mps1在多个步骤中帮助控制和指导染色体的方式，从聚集到微管附着，再到减数分裂中纺锤体的双向定位。该项目由分子和细胞生物科学部的细胞动力学和功能集群以及刺激竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The ability to accurately move chromosomes within the cell is crucial for an organism’s survival. Successful cell division depends upon first duplicating the genetic material contained within each chromosome, then actively partitioning the chromosomes into two exact sets, and finally dividing the cell so each daughter cell contains just one of the two chromosome sets. Sexually reproducing organisms have two types of cell division, mitosis and meiosis. Mitosis produces most cell types, whereas meiosis produces gametes. In both types of division, chromosome movement is achieved by attaching cables, called microtubules, to a connecting site on the chromosomes, called the kinetochore, and then shortening the cables to pull the chromosomes to their destinations. The cables grow as two arrays from opposite sides of the nucleus. To become attached to a cable end, the duplicated chromosome pair must first move towards the middle of the nucleus. The two types of chromosome segregating events, mitosis and meiosis, share several similarities, but the molecular basis for several of their differences are not known. Mps1 is a conserved protein that is essential in both mitosis and meiosis, but with meiosis-specific functions that may reveal fundamental differences in these processes. This project aims to distinguish the different roles and molecular mechanisms of Mps1 in mitosis and meiosis. Mps1 localizes to kinetochores and may control chromosome movements by activating other proteins to enable chromosome movements to the middle of the microtubule arrays, connections to microtubule ends and shortening of microtubules to move the chromosomes. This Project will have a Broader Impact by providing an opportunity for Oklahoma high school and college students to perform independent hypothesis-driven basic research projects. Students from local urban high schools will have the opportunity to perform year-long research projects in which they will investigate candidate proteins that might interact with Mps1 to control chromosome movements. Each summer in a residential research program, two students from rural areas of Oklahoma will be able to participate in an eight-week research internship investigating the mechanisms by which Mps1 controls chromosome movement. This project has the combined goal of advancing understanding of a sophisticated cellular process and introducing students to a culture of basic research.Accurate segregation of chromosomes on the mitotic or meiotic spindle depends upon a series of sequential steps. First chromosomes move towards the spindle mid-zone, a step called chromosome congression. Second correct kinetochore-microtubule (k-MT) attachments are formed. Then kinetochore microtubules depolymerize to promote poleward chromosome migration. But what are the signals that trigger these events? MPS1 encodes a conserved essential kinase that has been shown be involved in several key steps in cell cycle progression and chromosome segregation in both mitosis and meiosis in several organisms. Experiments from fission yeast and mammals suggest the hypothesis that Mps1 promotes chromosome gliding, a process that moves chromosomes to the spindle mid-zone in early prometaphase. In addition, in budding yeast meiosis, Mps1 is required for forming stable k-MT attachments, and is then needed to trigger MT de-polymerization to promote poleward chromosome movement. This project tests the hypothesis that Mps1 is a critical regulator of multiple sequential events in chromosome segregation in budding yeast meiosis. This project will elucidate novel mechanisms that drive ordered meiotic chromosome behavior. This project has three objectives. The first is to determine whether several functions of Mps1 are conserved in meiosis, including the MT-dependent sliding of chromosomes from the poles to the spindle mid-zone, termed chromosome gliding. This objective will also test the hypothesis that Mps1 is necessary for regulating this process and determine its regulatory targets. The second objective is to identify the roles that several protein phosphorylation targets of Mps1 have in the three sequential steps in the bi-orientation process: congression to the spindle mid-zone in early prometaphase, attachment of kinetochores to MTs, and depolymerization of kinetochore MTs to trigger poleward chromosome movements. The third objective takes advantage of a separation-of-function allele of MPS1 (mps1-R170S) that exhibits very mild mitotic defects, but profound meiotic defects. Suppressor mutations that improve meiotic chromosome segregation in mps1-R170S mutants have been isolated. These mutants will be evaluated to identify the pathways in meiosis that are extraordinarily sensitive to Mps1 function. Together these experiments will elucidate the manner in which Mps1 helps control and direct chromosomes at multiple steps, from congression, to microtubule attachment, to bi-orientation on the spindle in meiosis.This project is jointly funded by the Cellular Dynamics and Function cluster in the Division of Molecular and Cellular Biosciences, and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.