Drosophila roadblock and Chlamydomonas LC7: A conserved family of dynein-associated proteins involved in axonal transport, flagellar motility, and mitosis

Eukaryotic organisms utilize microtubule-dependent motors of the kinesin an d dynein superfamilies to generate intracellular movement. To identify new genes involved in the regulation of axonal transport in Drosophila melanoga ster, we undertook a screen based upon the sluggish larval phenotype of kno wn motor mutants. One of the mutants identified in this screen, roadblock ( robl), exhibits diverse defects in intracellular transport including axonal transport and mitosis. These defects include intra-axonal accumulations of cargoes, severe axonal degeneration, and aberrant chromosome segregation. The gene identified by robl encodes a 97-amino acid polypeptide that is 57% , identical (70% similar) to the 105-amino acid Chlamydomonas outer arm dyn ein-associated protein LC7, also reported here. Both robl and LC7 have homo logy to several other genes from fruit fly, nematode, and mammals, but not Saccharomyces cerevisiae. Furthermore, we demonstrate that members of this family of proteins are associated with both flagellar outer arm dynein and Drosophila and rat brain cytoplasmic dynein. WE: propose that: roadblock/LC 7 family members may modulate specific dynein functions.