Meiotic Functions of Mps1

在体细胞的生长过程中，有丝分裂将每条染色体的一个拷贝分配给每个子细胞。配子的产生需要一种特殊形式的染色体分配，即减数分裂，其中两轮连续的染色体分离产生配子，其染色体数目为体细胞的一半。减数分裂过程部分是通过对用于有丝分裂的细胞机器进行减数分裂特异性控制的特定水平分层来完成的。鉴定这些减数分裂特异性控制对于破译用于在减数分裂中实现高保真染色体分离的机制至关重要。MPS 1编码一种保守的、必需的激酶，其已被证明参与许多物种中有丝分裂和减数分裂细胞中染色体分离的几个关键步骤。MPS 1参与：1）主轴杆体的复制（在芽殖酵母中），组织微管组装成纺锤体的结构，纺锤体将分离的染色体拉开，2）参与纺锤体组装检查点机制，向细胞发出染色体不适当地附着在微管上的信号，3）介导这些不适当附着的释放，以便形成新的附着，和4）（在芽殖酵母中）促进孢子壁的适当组装。由于MPS 1蛋白的多重作用，MPS 1突变体通常具有复杂的表型，这些表型对于遗传研究来说没有信息。最近发现的一个特定的突变，mps 1-R170 S打开了大门，探索减数分裂特异性作用的Mps 1。mps 1-R170 S突变体在有丝分裂生长中具有非常轻微的缺陷，但在减数分裂中的染色体分离中具有灾难性的缺陷。msp 1-R170 S突变体在第一次和第二次减数分裂中都表现出非常高水平的染色体分离错误。因此，mps 1-R170 S只破坏了Mps 1的一些功能（减数分裂特异性功能），并提供了研究这些缺陷的机会，从而揭示Mps 1蛋白在减数分裂中的作用。初步数据表明，Mps 1在减数分裂中的作用有两种假说。本项目将检验这些假设。这两种假说中的任何一种，或者两者的结合，都可以解释观察到的mps 1-R170 S突变体的减数分裂行为。第一个假设是Mps 1在减数分裂中起着重要的作用，溶解kinetochore-microtubule附件。根据这一假设，着丝粒在减数分裂早期仅从一个纺锤体极体附着到微管，Mps 1需要释放这些附着，以便可以形成对两个纺锤体极体的附着。第二个假设是Mps 1是在减数分裂中释放姐妹染色单体之间的关联所必需的。根据这一假说，在减数分裂I中，姐妹染色单体的持续联合将同源染色体锁定在一起，迫使它们在减数分裂I中一起移动到一个纺锤极，并迫使姐妹染色单体在减数分裂II中移动到一个极。本建议的最后一个目标是使用遗传学方法来确定的合作伙伴Mps 1在meiosis.Broader影响：由于Mps 1是高度保守的，这些研究Mps 1在酵母减数分裂可能会揭示Mps 1功能的一般原则，有丝分裂和减数分裂染色体的行为，这是广泛适用于大多数真核生物。该项目将为一名博士后研究人员提供培训机会。此外，该项目还将用于为当地高中和本科培训项目的暑期学生提供独立的研究项目。在这个项目中，学生将学习遗传学的基础知识，同时有助于分析与减数分裂中Mps 1相互作用的基因。博士后研究员不仅将执行该项目的大部分实验，还将担任本科生/高中学员的导师。

During the growth of somatic cells, mitotic divisions partition one copy of each chromosome to each daughter cell. The production of gametes requires a special form of chromosome partitioning, meiosis, in which two sequential rounds chromosome segregation yield gametes with half the number of chromosomes of the somatic cells. The meiotic process is accomplished in part by layering specialized levels of meiosis-specific control upon the cellular machinery that is used for mitosis. Identifying these meiosis-specific controls is central to deciphering the mechanisms that are used to achieve high fidelity chromosome segregation in meiosis. MPS1 encodes a conserved, essential, kinase that has been shown be involved in several key steps in chromosome segregation in both mitotic and meiotic cells in many species. Mps1 is involved in: 1) duplication of the spindle pole body (in budding yeast), the structure that organizes the assembly of microtubules into the spindle that will pull the segregating chromosomes apart, 2) participation in the spindle assembly checkpoint mechanism that signals to the cell that a chromosome is attached inappropriately to microtubules, 3) mediating the release of these inappropriate attachments so that new ones can form, and 4) (in budding yeast) promoting the proper assembly of spore walls. Because of the multiple roles of Mps1 protein, MPS1 mutants often have complex phenotypes that are not informative for genetic studies. The recent discovery of a specific mutation, mps1-R170S has opened the door to exploring meiosis-specific roles for Mps1. mps1-R170S mutants have very mild defects in mitotic growth but catastrophic defects in chromosome segregation in meiosis. msp1-R170S mutants exhibit very high levels of chromosome segregation errors in both the first and second meiotic division. Thus the mps1-R170S destroys only some functions of Mps1 (meiosis-specific functions) and provides the opportunity to study those defects in ways that should reveal the role of the Mps1 protein in meiosis. Preliminary data suggest two hypotheses for the role of Mps1 in meiosis. This project will test these hypotheses. Either hypothesis, or a combination of the two, would explain the observed meiotic behavior mps1-R170S mutants. The first hypothesis is that Mps1 plays an essential meiotic role in dissolving kinetochore-microtubule attachments. By this hypothesis, kinetochores are attached early in both meiotic divisions to microtubules from only one spindle pole body and Mps1 is required to release these attachments so that attachments to both spindle pole bodies can be formed. The second hypothesis is that Mps1 is required to release an association between sister chromatids in meiosis. According to this hypothesis a persistent association of sister chromatids locks homologous chromosomes together in meiosis I, forcing them to move together to one spindle pole at meiosis I, and forcing sister chromatids to move to one pole at meiosis II. A final objective of this proposal is to use genetic approaches to identify the partners with which Mps1 interacts in meiosis.Broader Impacts: Because Mps1 is highly conserved, these studies of Mps1 in yeast meiosis may reveal general principles of Mps1 function, and mitotic and meiotic chromosome behavior, that are widely applicable to most eukaryotic organisms. The project will provide a training opportunity for one post-doctoral researcher. In addition, this project will be used to provide summer students, from a local high school and undergraduate training program, with independent research projects. In this program the students will learn fundamentals of genetics while contributing to the analysis of genes that interact with Mps1 in meiosis. The post-doctoral researcher will not only perform most of the experiments on the project but will serve as comentor for the undergraduate/high school trainees.