ANASTRAL MEIOTIC SPINDLE MORPHOGENESIS - ROLE OF THE NON-CLARET DISJUNCTIONAL KINESIN-LIKE PROTEIN

We have used time-lapse laser scanning confocal microscopy to directly examine microtubule reorganization during meiotic spindle assembly in living Drosophila oocytes. These studies indicate that the bipolarity of the meiosis I spindle is not the result of a duplication and separ ation of centrosomal microtubule organizing centers (MTOCs). Instead, microtubules first associate with a tight chromatin mass, and then bun dle to form a bipolar spindle that lacks asters. Analysis of mutant oo cytes indicates that the Non-Claret Disjunctional (NCD) kinesin-like p rotein is required for normal spindle assembly kinetics and stabilizat ion of the spindle during metaphase arrest. Immunolocalization analyse s demonstrate that NCD is associated with spindle microtubules, and th at the centrosomal components gamma-tubulin, CP-190, and CP-60 are not concentrated at the meiotic spindle poles. Based on these observation s, we propose that microtubule bundling by the NCD kinesin-like protei n promotes assembly of a stable bipolar spindle in the absence of typi cal MTOCs.