Biology subjects

Meyer, R. E.

Publications and source records attributed to Meyer, R. E..

4 recordsLinked to original sources

bioRxiv2023

Polyploid yeast are dependent on elevated levels of Mps1 for successful chromosome segregation

Tumor cell lines with elevated chromosome numbers frequently exhibit elevated expression of Mps1. These tumors are also dependent on high Mps1 activity for their survival. Mps1 is a conserved kinase involved in controlling aspects of chromosome segregation in mitosis and meiosis. The mechanistic explanation for the Mps1-addiction of aneuploid cells is unknown. To address this question, we explored Mps1-dependence in yeast cells with increased sets of chromosomes. These experiments revealed that in yeast, increasing ploidy leads to delays and failures in orienting chromosomes on the mitotic spindle. Yeast cells with elevated numbers of chromosomes proved vulnerable to reductions of Mps1 activity. Cells with reduced Mps1 activity exhibit an extended prometaphase with longer spindles and delays in orienting the chromosomes. One known role of Mps1 is in recruiting Bub1 to the kinetochore in meiosis. We found that the Mps1-addiction of polyploid yeast cells is due in part to its role in Bub1 recruitment. Together, the experiments presented here demonstrate that increased ploidy renders cells more dependent on Mps1 for orienting chromosomes on the spindle. The phenomenon described here may be relevant in understanding why high-ploidy cancer cells exhibit elevated reliance on Mps1 expression for successful chromosome segregation. AUTHOR SUMMARYLosing or gaining chromosomes during cell division leads to aneuploidy (an abnormal number of chromosomes) and can contribute to cancer and other diseases. Indeed, most cells in solid tumors carry abnormally elevated numbers of chromosomes. Mps1 is a regulator of the machinery that distributes chromosomes to daughter cells. In tumors with elevated chromosome numbers, the expression of Mps1 is often also elevated. In some aneuploid tumor cell lines these elevated Mps1 levels have been shown to be critical for tumor survival. To determine how cells with higher ploidy become dependent on Mps1, we explored Mps1-dependence in yeast cells with increased numbers of chromosomes. We report that yeast cells with elevated chromosome number are sensitive to reductions Mps1 expression. In cells with high ploidy and reduced levels of Mps1, the progression of the cell cycle is delayed and the ability of the cells to properly orient and segregate their chromosomes on the spindle is greatly reduced.

cell biology↗

bioRxiv2022

Centromere Pairing in Prophase Allows Partner Chromosomes to Orient on the Meiosis I Spindle

Proper chromosome segregation in meiosis I relies on the formation of connections between homologous chromosomes. Crossovers between homologs provide a connection that allows them to attach correctly to the meiosis I spindle. Tension is transmitted across the crossover when the partners attach to microtubules from opposing poles of the spindle. Tension stabilizes microtubule attachments that will pull the partners towards opposite poles at anaphase 1,2. Paradoxically, in many organisms, non-crossover partners segregate correctly 3. The mechanism by which non-crossover partners become bi-oriented on the meiotic spindle is unknown. Both crossover and noncrossover partners pair their centromeres in early in meiosis (prophase). In budding yeast, centromere pairing, is correlated with subsequent correct segregation of the partners 4,5. The mechanism by which centromere pairing, in prophase, promotes later correct attachment of the partners to the metaphase spindle is unknown. We used live cell imaging to track the bi-orientation process of non-crossover chromosomes. We find that centromere pairing allows the establishment of connections between the partners that allows their later interdependent attachment to the meiotic spindle using tensionsensing bi-orientation machinery. Because all chromosome pairs experience centromere pairing, our findings suggest that crossover chromosomes also utilize this mechanism to achieve maximal segregation fidelity.

cell biology↗

bioRxiv2020

Mps1 promotes poleward chromosome movements in meiotic pro-metaphase

In prophase of meiosis I, homologous partner chromosomes pair and become connected by crossovers. Chiasmata, the connections formed between the partners enable the chromosome pair, called a bivalent, to attach as a single unit to the spindle. When the meiosis I spindle forms in prometaphase, most bivalents are associated with a single spindle pole and go through a series of oscillations on the spindle, attaching to and detaching from microtubules until the partners of the bivalent are bi-oriented, that is, attached to microtubules from opposite sides of the spindle, and prepared to be segregated at anaphase I. The conserved, kinetochore-associated kinase, Mps1, is essential for the bivalents to be pulled by microtubules across the spindle in prometaphase. Here we show that MPS1 is not required for kinetochores to attach microtubules but instead is necessary to trigger the migration of microtubule-attached kinetochores towards the poles. Our data support the model that Mps1 triggers depolymerization of microtubule ends once they attach to kinetochores in prometaphase. Thus, Mps1 acts at the kinetochore to co-ordinate the successful attachment of a microtubule and the triggering of microtubule depolymerization to move the chromosome.

cell biology↗

bioRxiv2020

Mps1 expression is critical for chromosome orientation and segregation in yeast with high ploidy

In aneuploid cancer cells, the chromosome segregation apparatus is sensitive to increased chromosome number. The conserved protein kinase, Mps1, is a critical actor of this machinery, orienting the chromosomes properly on the spindle. Abnormally high levels of this kinase have been found in tumors with elevated chromosome number. However, it remains unclear, mechanistically, if and how cells with higher ploidy become dependent upon increased Mps1 levels. To answer these questions, we explored Mps1 dependence in yeast cells with increased sets of chromosomes. We discovered that having more chromosomes affects the ability of cells to orient chromosomes properly. The cells with increased numbers of chromosomes are particularly sensitive to the reduction of Mps1 activity. In mps1 loss of function mutants, cells display an extended prometaphase with a longer spindle and a delay in orienting properly the chromosomes. Altogether, our results suggest that increased numbers of chromosomes render cells more dependent on Mps1 for orienting chromosomes on the spindle. The phenomenon described here may be relevant in understanding why hyperdiploid cancer cells become excessively reliant on high Mps1 expression for successful chromosome segregation. Author summaryMost cells in solid tumors usually carry far more chromosomes than normal cells. Losing or gaining chromosomes during cell division can lead to aneuploidy (an abnormal number of chromosomes), cancer, and other diseases. Mps1 is a master regulator of cell division that is critical to keep the correct number chromosomes in each daughter cell. This master regulator has been shown to target and affect the function of various actors involved in cell division. Abnormally high levels of this master regulator are found in tumors with elevated chromosome numbers. The high levels of this regulator appear to be protecting these tumor cells. To answer if and how cells with higher ploidy become so dependent of Mps1, we generated yeast cells with increased set of chromosomes. Here, we report that cells with elevated chromosome number are particularly sensitive to the reduction of Mps1 level. In cells with higher ploidy and reduced level of Mps1, the progression during cell division is delayed. In the mutant cells, their ability to properly orient and segregate their chromosomes on the spindle is greatly reduced.

cancer biology↗