DROSOPHILA CYTOPLASMIC DYNEIN, A MICROTUBULE MOTOR THAT IS ASYMMETRICALLY LOCALIZED IN THE OOCYTE

The unidirectional movements of the microtubule-associated motors, dyn eins, and kinesins, provide an important mechanism for the positioning of cellular organelles and molecules. An intriguing possibility is th at this mechanism may underlie the directed transport and asymmetric p ositioning of morphogens that influence the development of multicellul ar embryos. In this report, we characterize the Drosophila gene, Dhc64 C, that encodes a cytoplasmic dynein heavy chain polypeptide. The prim ary structure of the Drosophila cytoplasmic dynein heavy chain polypep tide has been determined by the isolation and sequence analysis of ove rlapping cDNA clones. Drosophila cytoplasmic dynein is highly similar in sequence and structure to cytoplasmic dynein isoforms reported for other organisms. The Dhc64C dynein transcript is differentially expres sed during development with the highest levels being detected in the o varies of adult females. Within the developing egg chambers of the ova ry, the dynein gene is predominantly transcribed in the nurse cell com plex. In contrast, the encoded dynein motor protein displays a strikin g accumulation in the single cell that will develop as the oocyte. The temporal and spatial pattern of dynein accumulation in the oocyte is remarkably similar to that of several maternal effect gene products th at are essential for oocyte differentiation and axis specification. Th is distribution and its disruption by specific maternal effect mutatio ns lends support to recent models suggesting that microtubule motors p articipate in the transport of these morphogens from the nurse cell cy toplasm to the oocyte.