ADrosophilaKinesin-like Protein, Klp38B, Functions during Meiosis, Mitosis, and Segmentation

AbstractWe show thatklp38B,isolated as a mutation that dominantly prolongs blastoderm mitotic cycles in Drosophila, encodes a Drosophila kinesin-like protein. Further genetic analyses show that Klp38B not only functions during mitosis, but is also required for meiosis and abdominal segmentation. Sequence comparisons suggest that Klp38B encodes an amino-terminal microtubule motor domain, a central α-helical coiled-coil domain, and a C-terminal globular domain. Evidence that Klp38B is required during meiosis is that flies transheterozygous for mutations in bothklp38Bandnodhave a high frequency of 4th chromosome meiotic nondisjunction. Nod is a chromokinesin, a chromosome binding kinesin, that is believed to provide astral-exclusion forces during the metaphase stage of meiosis. Evidence that Klp38B is required during mitosis is that embryos from female germline clones ofklp38Bmutations have holes in the cuticle similar to a zygoticstring(dCDC25) phenotype. Also, anti-Klp38B antibody injection into precellularization blastoderm embryos causes developmental arrest and the formation of circular mitotic figures. We speculate, based on these phenotypes, that Klp38B is a chromokinesin that provides astral-exclusion forces on the chromosomes during meiosis and mitosis. Consistent with this hypothesis, we have identified an HMG-1 homologous region on Klp38B that could potentially bind AT-rich DNA sequences. Finally, we show thatklp38Bmutations have defects in abdominal segmentation, suggesting that Klp38B, like Xenopus chromokinesin Xklp1, might be involved in polar granule formation