We describe here a new member of the kinesin superfamily in Drosophila, KLP3A (Kinesin-Like-Protein-at-3A). The KLP3A protein localizes to the equator of the central spindle during late anaphase and telophase of male meiosis. Mutations in the KLP3A gene disrupt the interdigitation of microtubules in spermatocyte central spindles. Despite this defect, anaphase B spindle elongation is not obviously aberrant. However, cytokinesis frequently fails after both meiotic divisions in mutant testes. Together, these findings strongly suggest that the KLP3A presumptive motor protein is a critical component in the establishment or stabilization of the central spindle. Furthermore, these results imply that the central spindle is the source of signals that initiate the cleavage furrow in higher cells.

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