During mitosis, many structural, regulatory, and checkpoint proteins work towards the goal of accomplishing equal chromosome segregation. Microtubules of the mitotic spindle attach to kinetochores on chromosomes, and this attachment of microtubules to all kinetochores on all chromosomes provides a checkpoint signal that instructs the cell to undergo chromosome segregation. A protein called Spindly was previously known to localize the microtubule motor dynein to kinetochores. A recent paper has found an additional role for Spindly in coordinating microtubule attachment to kinetochores and mitotic checkpoint signaling. Image above shows mitotic spindles (PM, M) in control cells and cells with lower levels of Spindly. In cells with decreased Spindly, mitotic spindles are often abnormal – some are longer (L), some have more than two spindle poles (MP), and some are twisted (T). DNA is in blue, microtubules are in green, and kinetochores are in red.
Reference: Marin Barisic, Bénédicte Sohm, Petra Mikolcevic, Cornelia Wandke, Veronika Rauch, Thomas Ringer, Michael Hess, Günther Bonn, and Stephan Geley. Authors’ Molecular Biology of the Cell paper can be found here.
Is there any ideas out there why a decrease in Spindly concentration affects miotic spindles differences? It seems like a very wide range of issues it causes
ReplyDeleteThanks, Kevin! Based on their paper (which you need a subscription to access, unfortunately), it sounds like the authors think that for some of the abnormalities, the lack of Spindly is causing mechanical damage due to the spindle rotating, leading to nonspecific problems. The elongated spindles, though, they think are because the attachments between the microtubules in the spindle and each kinetochore aren't quite normal. Thanks for letting me geek out!
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