We have developed two new assays of nematode chemotaxis (see abstract Stephen Wicks). The first gene identified and cloned using these assays was a cytosolic isoform (1B subfamily) of the dynein heavy chain. Complementation studies show that this dynein heavy chain is the CHE-3 protein. Previously, this isoform of the dynein heavy chain was shown to be expressed during cilia outgrowth in sea urchins (Gibbons, 1994), and involved in the organisation of the Golgi-apparatus in non-ciliated human cell lines (Vaisberg, 1996). GFP expression studies indicate that
che-3 is expressed exclusively in all ciliated sensory neurons in the worm. The highest levels of
che-3 expression are correlated with outgrowth of cilia. To visualise the structure of ciliated endings we used two GFP markers of amphid and phasmid integrity (GPA-13::GFP and GPA-15::GFP, as integrated transgenes, gifts of Gert Jansen). These markers indicate that the amphid and phasmid cilia are malformed in the worm, and that the degree of disorganisation appears to increase as the animal ages. These results suggest that dynein heavy chain has a function in cilia outgrowth in C. elegans, but has no role in the organisation of the Golgi apparatus in the worm. Gibbons, B.H., Asai, D.J., Wen-Jing, Y., Hays, T.S., and Gibbons, I.R. (1994). Phylogeny and expression of axonemal and cytoplasmic dynein genes in sea urchins. Mol. Biol. Cell 5, 57-70. Vaisberg, E.A., Grissom, P.M., and McIntosh, J.R. (1996). Mammalian cells express three distinct dynein heavy chains that are localized to different cytoplasmic organelles. J. Cell Biol. 133, 831-842.