Lane SIR, Jones KT. Chromosome biorientation and APC activity remain uncoupled in oocytes with reduced volume.
J Cell Biol 2017;
216:3949-3957. [PMID:
28978643 PMCID:
PMC5716262 DOI:
10.1083/jcb.201606134]
[Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 07/28/2017] [Accepted: 09/07/2017] [Indexed: 11/23/2022] Open
Abstract
Lane and Jones use serial bisection of mouse oocytes to analyze the influence of cytoplasmic volume on spindle assembly checkpoint function. Volume reduction promotes inhibition of APC but cannot prevent chromosome segregation errors at anaphase.
The spindle assembly checkpoint (SAC) prevents chromosome missegregation by coupling anaphase onset with correct chromosome attachment and tension to microtubules. It does this by generating a diffusible signal from free kinetochores into the cytoplasm, inhibiting the anaphase-promoting complex (APC). The volume in which this signal remains effective is unknown. This raises the possibility that cell volume may be the reason the SAC is weak, and chromosome segregation error-prone, in mammalian oocytes. Here, by a process of serial bisection, we analyzed the influence of oocyte volume on the ability of the SAC to inhibit bivalent segregation in meiosis I. We were able to generate oocytes with cytoplasmic volumes reduced by 86% and observed changes in APC activity consistent with increased SAC control. However, bivalent biorientation remained uncoupled from APC activity, leading to error-prone chromosome segregation. We conclude that volume is one factor contributing to SAC weakness in oocytes. However, additional factors likely uncouple chromosome biorientation with APC activity.
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