Linking Centromere Stretch to SAC Signaling in Mammalian Oocytes: Insights from a Kinetochore-Modified Model

The spindle assembly checkpoint (SAC) monitors kinetochore-microtubule interactions to ensure accurate chromosome segregation. In mitosis, investigation of its silencing at anaphase centers on whether attachment or tension is the key signal, while in meiosis for mammalian oocytes it remains unclear whether centromere stretching contributes to SAC deactivation, because in this reductional division sister chromatids co-segregate during meiosis I. While previous studies have linked bivalent tension to SAC control in oocytes, this measurement cannot be directly equated with mitotic chromatin stretching. Here, by tagging the N-terminus of NDC80/HEC1, we developed a mouse oocyte model that features stable microtubule attachments, yet exhibits persistent SAC signaling at metaphase I. Our comprehensive analysis revealed a strong correlation between centromere stretching and SAC signaling. Furthermore, high-resolution live imaging demonstrated that these modified kinetochores impaired their oscillatory movements, a process vital for error correction, while chromosome congression remained largely unaffected. Collectively, our data suggest that stable microtubule attachment alone is insufficient to silence SAC in mammalian oocytes; instead, centromere stretching may serve as a critical signal to deactivate the checkpoint. These findings underscore the adaptability of core cell-cycle surveillance pathways.