Cytoplasmic dynein is required for the nuclear attachment and migration ofcentrosomes during mitosis in Drosophila

Cytoplasmic dynein is a multisubunit minusend-directed microtubule motor th at serves multiple cellular functions. Genetic studies in Drosophila and mo use have demonstrated that dynein function is essential in metazoan organis ms. However, whether the essential function of dynein reflects a mitotic re quirement, and what specific mitotic tasks require dynein remains controver sial. Drosophila is an excellent genetic system in which to analyze dynein function in mitosis, providing excellent cytology in embryonic and somatic cells. We have used previously characterized recessive lethal mutations in the dynein heavy chain gene, Dhc64C, to reveal the contributions of the dyn ein motor to mitotic centrosome behavior in the syncytial embryo. Embryos l acking wild-type cytoplasmic dynein heavy chain were analyzed by in vivo an alysis of rhodamine-labeled microtubules, as well as by immunofluorescence in situ methods. Comparisons between wild-type and Dhc64C mutant embryos re veal that dynein function is required for the attachment and migration of c entrosomes along the nuclear envelope during interphase/prophase, and to ma intain the attachment of centrosomes to mitotic spindle poles. The disrupti on of these centrosome attachments in mutant embryos reveals a critical rol e for dynein function and centrosome positioning in the spatial organizatio n of the syncytial cytoplasm of the developing embryo.