We have previously reported the cloning of
che-3 and shown that it encodes a dynein heavy chain (DHC). Comparison with the available (mostly partial) DHC sequences shows that CHE-3 is a member of the novel 1b isotype of DHCs, most closely related to Chlymandomonas , sea urchin and mammalian genes implicated in axonemal and intraflagellar transport during cilia synthesis and regeneration. To explore this apparent sequence and perhaps functional homology further we obtained partial sequence of the
che-3 homologues in other nematodes ( Caenorhabditis briggsae, Ostertagia circumcincta, Onchocerca volvulus & Parastrongyloides trichosuri ). Alignment of these sequences with typical cytoplasmic and isotype 1b DHCs reveals several sites where all of the 1b sequences display the same amino acid substitution relative to the cytoplasmic dynein heavy chain sequences. This, together with the defective amphid phenotype of
che-3 mutants suggests that
che-3 defines a novel, conserved class of DHC that is required for the generation of cilia in C. elegans chemosensory neurones. There are mammalian nervous system EST's with strong homology to
che-3 , raising the possibility that
che-3 homologues function in the mammalian sensory nervous system.