title: Meiotic competence acquisition is associated with the appearance of M-phase characteristics in growing mouse oocytes.
abstract: To determine whether the acquisition of meiotic competence during the growth phase of oogenesis is associated with the appearance of M-phase characteristics, oocytes obtained from 13- to 30-day-old mice were evaluated by fluorescence microscopy with respect to chromatin and microtubule organization , in vitro maturation ability, and the distribution of M-phase phosphoproteins. Meiotically incompetent oocytes were distinguished from their competent counterparts in displaying elaborate interphase-like arrays of cytoplasmic microtubules and dispersed germinal vesicle chromatin. Meiotically competent oocytes were larger in size, exhibited condensation of chromatin around the nucleolus, and displayed a progressive diminution of cytoplasmic microtubules in conjunction with the appearance of multiple microtubule organizing centers. After 24 hr in culture, medium- to large-sized oocytes exhibiting perinucleolar chromatin condensation resume meiosis whereas smaller meiotically incompetent oocytes retain GVs with diffuse chromatin. Moreover, indirect immunofluorescence studies using the M-phase phosphoprotein specific monoclonal antibody MPM-2 indicate that the appearance of reactive cytoplasmic foci is directly correlated with nuclear changes characteristic of meiotically competent oocytes. Thus, the earliest transition to a meiotically competent state during oocyte growth in the immature mouse ovary is characterized by stage-specific and coordinated modifications of nuclear and cytoplasmic components.
authors.affiliation: Tufts University Health Science Schools, Department of Anatomy and Cellular Biology, School of Medicine, Boston, Massachusetts 02111.
authors.forename: D
authors.initials: D
authors.lastname: Wickramasinghe
authors.forename: K M
authors.initials: KM
authors.lastname: Ebert
authors.forename: D F
authors.initials: DF
authors.lastname: Albertini
mesh_terms: D000818:Animals; D005260:Female; D008540:Meiosis; D051379:Mice; D008856:Microscopy, Fluorescence; D008938:Mitosis; D009865:Oocytes / Q000166:cytology* / Q000254:growth & development; D009866:Oogenesis