MICROTUBULE MEDIATION OF CYTOPLASMIC AND NUCLEAR MATURATION DURING THE EARLY STAGES OF RESUMED MEIOSIS IN CULTURED MOUSE OOCYTES

A perinuclear accumulation of mitochondria characterizes the premetaphase I stages of reinitiated meiosis in the laboratory mouse oocyte. The cellular basis of this organelle-specific translocation was examined by fluorescent probe analysis, immunostaining, and immunoelectron microscopy in oocytes cultured at specific stages of meiotic maturation in the presence and absence of drugs that influence the stability of microfilaments and microtubules. The results suggest that a temporal, spatial, and developmental relationship exists between the location of microtubule organizing centers and the progressive translocation of mitochondria to the nuclear region. The findings indicate that mitochondrial translocations are mediated by microtubules and that individual microtubule organizing centers are not only foci for mitochondrial aggregation but may also facilitate the establishment of the circular bivalent configuration.