Drosophila roadblock and Chlamydomonas Lc7

Eukaryotic organisms utilize microtubule- dependent motors of the kinesin and dynein superfami- lies to generate intracellular movement. To identify new genes involved in the regulation of axonal trans- port in Drosophila melanogaster , we undertook a screen based upon the sluggish larval phenotype of known 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 accumula- tions of cargoes, severe axonal degeneration, and aber- rant chromosome segregation. The gene identified by robl encodes a 97-amino acid polypeptide that is 57% identical (70% similar) to the 105-amino acid Chlamy- domonas outer arm dynein-associated protein LC7, also reported here. Both robl and LC7 have homology to several other genes from fruit fly, nematode, and mammals, but not Saccharomyces cerevisiae . Further- more, we demonstrate that members of this family of proteins are associated with both flagellar outer arm dynein and Drosophila and rat brain cytoplasmic dy- nein. We propose that roadblock/LC7 family members may modulate specific dynein functions.