Sa. Connors et al., INVOLVEMENT OF THE CYTOSKELETON IN THE MOVEMENT OF CORTICAL GRANULES DURING OOCYTE MATURATION, AND CORTICAL GRANULE ANCHORING IN MOUSE EGGS, Developmental biology (Print), 200(1), 1998, pp. 103-115
Exocytosis of cortical granules in mouse eggs is required to produce t
he zona pellucida block to polyspermy. In this study, we examined the
role of microfilaments and microtubules in the regulation of cortical
granule movement toward the cortex during oocyte maturation and anchor
ing of cortical granules in the cortex. Fluorescently labeled cortical
granules, microfilaments, and microtubules were visualized using lase
r-scanning confocal microscopy. It was observed that cortical granules
migrate to the periphery of the oocyte during oocyte maturation. This
movement is blocked by the treatment of oocytes with cytochalasin D,
an inhibitor of microfilament polymerization, but not with nocodazole
or colchicine, inhibitors of microtubule polymerization. Cortical gran
ules, once anchored at the cortex, remained in the cortex following tr
eatment of metaphase II-arrested eggs with each of these inhibitors; i
.e., there was neither inward movement nor precocious exocytosis. Fina
lly, the single cortical granule-free domain that normally becomes loc
alized over the metaphase II spindle was not observed when the chromos
omes become scattered following microtubule disruption with nocodazole
or colchicine. In these instances a cortical granule-free domain was
observed over each individual chromosome, suggesting that the chromoso
me or chromosome-associated material, and not the spindle, dictates th
e localization of the cortical granule-free domain. (C) 1998 Academic
Press.