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Mitotic and meiotic spindle dynamics comparison in fission yeast

Abstract : Cell division is a universal process in all living beings where duplicated chromosomes are separated to the opposite cell poles. Mitosis is a cell division type that serves for proliferation of cells, while meiosis produces sex cells, which are used in the sexual reproduction of an organism. In both cases, a microtubule-based machine called a spindle flawlessly separates the chromosomes. Precise chromosome separation is paramount, as any errors in chromosome segregation can result in aneuploidy that may cause congenital defects, cancer or cell death.Mitosis and meiosis have been the focus of research for many decades, and a plethora of key players has been identified and studied. However, no study has been done on comparison of mitotic and meiotic spindle dynamics in the same organism. In this study, mitotic and meiotic spindle dynamics have been characterized and compared simultaneously in fission yeast. Spindle dynamics comparison ascertained that there are three distinct spindle types – mitotic, meiotic I and meiotic II spindles, with distinguishing features. A fission yeast mutant deficient for kinesin-5 Cut7 and kinesin-14 Pkl1 was used as a tool to identify the source of the differences in mitotic and meiotic spindle dynamics. Although cut7Δpkl1Δ mitotic spindles are bipolar and capable of segregating the chromosomes, we show that meiosis I spindles fail to establish bipolarity and separate the chromosomes, resulting in zygotes forming less than typical four spores. Next, we reveal Pkl1 concentration is reduced in meiotic I compared to mitotic spindles, and identify kinesin-14 Klp2 as the molecule that co-operates with Pkl1 in antagonizing Cut7 in meiosis I. Furthermore, we found that suppressing microtubule dynamics in cut7Δpkl1Δ zygotes restores spindle bipolarity, arguing that microtubules are more dynamic in meiosis I spindles than in mitotic spindles.In summary, this work shows mitotic and meiotic spindles are inherently different, and their differences stem from kinesin-14s and microtubule dynamics regulation.
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Submitted on : Friday, March 19, 2021 - 3:30:00 PM
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Ana Loncar. Mitotic and meiotic spindle dynamics comparison in fission yeast. Cellular Biology. Université Paris sciences et lettres, 2020. English. ⟨NNT : 2020UPSLT003⟩. ⟨tel-03174872⟩

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