Subcellular distribution of aster-nucleated microtubule length: A more or less mitotic status of cytoplasmic areas during meiosis I of starfish oocytes

Summary— Shortening of aster-nucleated microtubules is a mitotic feature, which is proportional to the M-phase promoting factor kinase activity. We have taken advantage of this characteristic to appraise the mitotic status of cytoplasmic territories in polyspermic starfish oocytes. In early prometaphase, asters are small in the nuclear area, where cyclin B accumulated before GVBD, while in the remaining of the oocytes asters are large. In metaphase all asters are small. This coincides with a change in behaviour of cyclin B, whose association with microtubules increases in late prometaphase. We discuss the possibility that uneven distribution of cyclin B-dependent kinase is a general feature of mitosis and that it allows the cell to build the convenient spindle at the right place.