Microtubule assembly after treatment of pig oocytes with taxol: Correlation with chromosomes, gamma-tubulin, and MAP kinase

In this study, taxol was used as a tool to study the correlation of microtu bule assembly with chromosomes, gamma -tubulin and phosphorylated mitogen-a ctivated protein (MAP) kinase in pig oocytes at different maturational stag es. Taxol treatment did not affect meiotic resumption and chromosome conden sation but inhibited/disrupted chromosome alignment at the metaphase plate and bipolar spindle formation and thus meiotic progression. Microtubules we re co-localized with chromosomes and were found to emanate from the chromos omes in taxol-treated oocytes, suggesting that chromosomes may serve as a s ource of microtubule organization. In addition, the concentric emanation of microtubules within the chromosome-surrounded area in taxol-treated oocyte s suggests that microtubule emanation from the chromosomes may be directed by other microtubule-organizing material. The formation of one large spindl e or greater than or equal to2 spindles in oocytes after taxol removal show s that minus end microtubule-organizing material can be normally located on both sides of chromosomes only when the chromosomes are aligned on the met aphase plate. The co-localization of gamma -tubulin and phosphorylated MAP kinase with microtubule assembly in both control and taxol-treated oocytes suggests that these two proteins are associated microtubule-nucleating mate rial in pig oocytes. However, Western blot analysis showed that neither cyt oplasmic microtubule aster formation nor extensive microtubule assembly in the chromosome region induced by taxol was caused by super-activation of MA P kinase. Taxol also induced microtubule assembly depending on chromosome d istribution in the first polar body. The results suggest that chromosomes a re always co-localized with microtubules and that emanation of microtubules from the chromosomes may be regulated/directed by microtubule-organizing m aterial including gamma -tubulin and phosphorylated MAP kinase in pig oocyt es. Mol. Reprod. Dev, 60: 481-490, 2001. (C) 2001 Wiley-Liss, Inc.