Abstract
Oocytes vitrification is frequently applied in assisted reproductive technologies. However, chromosomes segregation was error-prone during meiosis maturation of vitrified oocytes. The fidelity of chromosomes segregation depends on the correct kinetochore-microtubule attachments (KT-MTs). In meiosis I, the Aurora B/C would not spatially separate from the attachment sites upon bivalents stretched. Oocytes lack a mechanism for coordinating bivalent stretching and Aurora B/C inhibition in meiosis I. Thus, the KT-MTs are unstable in oocytes. In this study, we firstly found the incorrect KT-MTs were markedly increased in vitrified oocytes. The Aurora B/C activity in vitrified oocytes was significantly increased when the bivalents were stretched. This Aurora B/C activity could not induce a SAC response, as the SAC protein Mad2 was significantly decreased during MI stage in vitrified oocytes. Thus, the KT-MTs in vitrified oocytes were error-prone. This study, for the first time, revealed the mechanism of the incorrect KT-MTs occurred in vitrified oocytes and provided a theoretical basis for further improvement of oocytes vitrification.
Highlights
The fidelity of chromosomes segregation depends on correct kinetochore-microtubule attachments (KT-MTs) (Tauchman et al, 2015)
The fluorescence intensity of pS55-Hec1 Mad2 and Securin-GFP was quantified according to the previous study (Vallot et al, 2018): manually built a 10 × 10 pixel box to put the centromere signal in center and quantified the intensity of centromere, turn to pS55-Hec1 or Mad2 channel to quantify the intensity; another 10 × 10 pixels box was put adjacent to the first box to quantified the background signal in each channel
Our results showed that the incorrect KT-MTs were markedly increased in vitrified oocytes
Summary
The fidelity of chromosomes segregation depends on correct kinetochore-microtubule attachments (KT-MTs) (Tauchman et al, 2015). In mitosis, when the kinetochores were correctly attached to microtubules, the tension would drive spatially separation of kinetochores from Aurora B/C, contributing to the stabilization of correct KTMTs (Lampson and Cheeseman, 2011; Foley and Kapoor, 2013). In meiosis I, the Aurora B/C did not spatially separate from the attachment sites during bivalents stretching (Yoshida et al, 2015). In Meiosis I, the correct KTMTs were eventually stabilized through PP2A-B56 phosphatase, which was recruited onto kinetochores to counteract Aurora B/C activity (Yoshida et al, 2015). Treatment of oocytes with Aurora B/C inhibitor AZD1125 at the middle of the stretching phase (3 h after GVBD), the correct KT-MTs were dramatically increased at the end of the stretching phase (4 h after GVBD) (Yoshida et al, 2015)
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