Spindle assembly without spindle pole body insertion into the nuclear envelope in fission yeast meiosis
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Centrosomes represent the major microtubule organizing center (MTOC) in eukaryotic cells and are responsible for nucleation of the spindle, the vehicle of chromosome segregation. In human female meiosis, however, spindle assembly occurs in the absence of centrosomes or other MTOCs and microtubules are nucleated around chromosomes. In yeast, spindle formation in mitosis and meiosis depends on the activity of spindle pole bodies (SPBs), the functional equivalents of centrosomes; thus, SPBs and centrosomes use similar machineries to assemble spindles. Here, we develop a system to explore the molecular mechanisms supporting acentrosomal spindle formation using fission yeast meiosis as a model scenario. We achieve this situation by removing access of the SPBs to the nucleus after their duplication. Under these conditions, we observe self-assembly-based spindle formation in the nuclear environment, conferring an ability to segregate chromosomes independently of the SPBs. Our results open the possibility to utilize the experimental advantages of fission yeast for insights into the molecular basis of acentrosomal spindle formation in meiosis.
KeywordsSpindle Meiosis Fission yeast Centrosome Spindle pole body
spindle pole body
nuclear envelope breakdown
We thank Julie Cooper, María Almuedo-Castillo, and Isabel Almudí for critical comments on the manuscript; Yesica García for technical support; and the CABD microscopy facility technician Katherina García for their helpful advice. We would like to thank the Genetics Department for their useful discussions and comments, especially Rafael R. Daga, Juan Jiménez, and Jose Ignacio Ibeas; and Víctor Manuel Carranco Fabre for the graphic design in the figures and technical support.
This work was supported by Spanish Government (Ramon y Cajal program, RyC-2016-19659) to AF-A; AP-S by Pablo de Olavide University Fellowship (PPI1807). The CABD is an institution funded by Pablo de Olavide University, Consejo Superior de Investigaciones Científicas (CSIC) and Junta de Andalucía.