Stable kinetochore–microtubule attachments restrict MTOC position and spindle elongation in oocytes. (3rd March 2021)

• Record Type: Journal Article
• Authors: Courtois, Aurélien; Yoshida, Shuhei; Takenouchi, Osamu; Asai, Kohei; Kitajima, Tomoya S
• Is Part Of: EMBO reports. Volume 22:Number 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-03-03
• Subjects: kinetochore -- microtubule -- MTOC -- oocyte -- spindle; Molecular biology -- Periodicals; Molecular Biology -- Periodicals; Molecular biology; Periodicals; 572.8
• DOI: 10.15252/embr.202051400
• Languages: English
• ISSNs: 1469-221X

Abstract

Abstract: In mouse oocytes, acentriolar MTOCs functionally replace centrosomes and act as microtubule nucleation sites. Microtubules nucleated from MTOCs initially assemble into an unorganized ball‐like structure, which then transforms into a bipolar spindle carrying MTOCs at its poles, a process called spindle bipolarization. In mouse oocytes, spindle bipolarization is promoted by kinetochores but the mechanism by which kinetochore–microtubule attachments contribute to spindle bipolarity remains unclear. This study demonstrates that the stability of kinetochore–microtubule attachment is essential for confining MTOC positions at the spindle poles and for limiting spindle elongation. MTOC sorting is gradual and continues even in the metaphase spindle. When stable kinetochore–microtubule attachments are disrupted, the spindle is unable to restrict MTOCs at its poles and fails to terminate its elongation. Stable kinetochore fibers are directly connected to MTOCs and to the spindle poles. These findings suggest a role for stable kinetochore–microtubule attachments in fine‐tuning acentrosomal spindle bipolarity. Synopsis: Stable kinetochore–microtubule attachments are required for confining MTOC positions at the spindle poles and for limiting spindle elongation during meiosis I in mouse oocytes. Early bipolar‐shaped spindles frequently exhibit small MTOCs in their central region. During metaphase, the majority of MTOCs are positioned at the poles of the bipolar‐shaped spindle. A small population of MTOCs are found in the central region of the spindle until they are eventually sorted to the poles. Reducing the stability of kinetochore–microtubule attachments with a phospho‐mimetic mutant of Ndc80 leads to defects in restricting MTOCs at the spindle poles and in terminating spindle elongation. Stable kinetochore fibers (K‐fibers) are directly connected to MTOCs and to spindle poles. Abstract : Stable kinetochore–microtubule attachments are required for confining MTOC positions at the spindle poles and for limiting spindle elongation during meiosis I in mouse oocytes.