Abstract
The spindle apparatus segregates bi-oriented sister chromatids during mitosis but mono-oriented homologous chromosomes during meiosis I. It has remained unclear if similar molecular mechanisms operate to regulate spindle dynamics during mitosis and meiosis I. Here, we employed live-cell microscopy to compare the spindle dynamics of mitosis and meiosis I in fission yeast cells and demonstrated that the conserved kinesin-14 motor Klp2 plays a specific role in maintaining metaphase spindle length during meiosis I but not during mitosis. Moreover, the maintenance of metaphase spindle stability during meiosis I requires the synergism between Klp2 and the conserved microtubule cross-linker Ase1, as the absence of both proteins causes exacerbated defects in metaphase spindle stability. The synergism is not necessary for regulating mitotic spindle dynamics. Hence, our work reveals a new molecular mechanism underlying meiotic spindle dynamics and provides insights into understanding differential regulation of meiotic and mitotic events.
Highlights
During meiosis, duplicated chromosomes are segregated into daughter cells to form haploid gametes through two rounds of successive cell division [1]
We first employed live-cell microscopy to analyze the spindle dynamics of mitosis and meiosis I in fission yeast cells expressing Sid4-GFP and mCherry-Atb2 (a-tubulin)
We compared mitotic and meiotic spindle dynamics in a quantitative manner and showed that Klp2 plays a crucial role in regulating spindle and chromosome dynamics during meiosis I but not during mitosis
Summary
During meiosis, duplicated chromosomes are segregated into daughter cells to form haploid gametes through two rounds of successive cell division [1]. We noticed that the average Ase1-GFP intensity along the spindle was generally weaker in WT mitotic cells than in WT meiotic cells (Fig. 3F), suggesting that more Ase1 molecules are concentrated on the preanaphase spindle, presumably within the antiparallel interpolar microtubules, during meiosis I than during mitosis. These results suggest that Klp2 plays a crucial role in organizing the interpolar microtubules within the meiotic spindles during preanaphase I, likely through regulating the localization of Ase1.
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