Distribution of microtubules during the first meiotic cell division in the mouse oocyte: effect of taxol.

Mouse oocytes were stained by antitubulin antibody and by an anti-MAP1 antibody (JA2) during the first meiotic cell division. At germinal vesicle stage, JA2 antibody exclusively stains the nucleoplasm. When the nuclear envelope breaks down (GVBD) (2-3 h of culture), numerous foci of microtubules appear around the disrupting nuclear envelope; they are decorated by anti-MAP1 antibody. After 10-12 h of culture, the antigen component detected with anti-MAP1 antibody is present in the meiotic spindle. The antimitotic agent taxol (10 microns) induces microtubule formation, mainly at the periphery of the germinal vesicle. At GVBD, taxol provokes the formation of a large microtubular array stained with both antibodies, which is associated with the condensed chromosomes. Furthermore, numerous cytoplasmic asters become visible in the cytoplasm. At metaphases I and II, taxol induces an important enlargement of the metaphase spindles and increases the number of cytasters.