Abstract
BackgroundHomologous chromosomes separate in meiosis I and sister chromatids separate in meiosis II, generating haploid gametes. To address the question why sister chromatids do not separate in meiosis I, we explored the roles of Shogoshin1 (Sgo1) in chromosome separation during oocyte meiosis.Methodology/Principal FindingsSgo1 function was evaluated by exogenous overexpression to enhance its roles and RNAi to suppress its roles during two meioses of mouse oocytes. Immunocytochemistry and chromosome spread were used to evaluate phenotypes. The exogenous Sgo1 overexpression kept homologous chromosomes and sister chromatids not to separate in meiosis I and meiosis II, respectively, while the Sgo1 RNAi promoted premature separation of sister chromatids.ConclusionsOur results reveal that prevention of premature separation of sister chromatids in meiosis I requires the retention of centromeric Sgo1, while normal separation of sister chromatids in meiosis II requires loss of centromeric Sgo1.
Highlights
One of the major differences between meiosis and mitosis is that the former consists of two consecutive rounds of chromosome separation with only one round of DNA replication, in which chromosome number is reduced to half to produce haploid gametes
Our results reveal that prevention of premature separation of sister chromatids in meiosis I requires the retention of centromeric Sgo1, while normal separation of sister chromatids in meiosis II requires loss of centromeric Sgo1
To characterize the roles of Sgo1 in chromosome separation during mouse oocyte meiosis, due to the lack of working antibody in mice, low concentration of (#0.4 mg/ml) Myc6-Sgo1 mRNA was injected into oocytes to examine the dynamics of Sgo1 localization at metaphase and anaphase of both meiotic divisions
Summary
One of the major differences between meiosis and mitosis is that the former consists of two consecutive rounds of chromosome separation with only one round of DNA replication, in which chromosome number is reduced to half to produce haploid gametes. To characterize the roles of Sgo1 in chromosome separation during mouse oocyte meiosis, due to the lack of working antibody in mice, low concentration of (#0.4 mg/ml) Myc6-Sgo1 mRNA was injected into oocytes to examine the dynamics of Sgo1 localization at metaphase and anaphase of both meiotic divisions. During the anaphase of the first meiosis (AI), Sgo1 signals were only detected on the centromeres of sister chromatids, until up to the metaphase of the second meiosis (MII), while no sgo1 signals were observed on arm (Fig. 1c and d, insets).
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