In all eukaryotes, kinesins are cytoskeletal motor proteins that mediate intracellular transport of a variety of vesicles and cellular cargo on microtubule tracks, using ATP hydrolysis. After the initial discovery of the kinesin heavy chain (KHC), a large family of kinesin like proteins has been discovered. In C. elegans using degenerate primers to the conserved ATP and microtubule binding sites, we have characterized cDNA clones corresponding to 20 genes (
klp-1 to
klp-20) encoding members of the kinesin superfamily (Khan et al., 1997). Several key questions immediately arise, such as how many different kinesins exist in one organism or cell type? Are multiple kinesins redundant or do they perform non-overlapping functions? Do other proteins exist, unrelated to the KHC, but associated with kinesins to form multimers in vivo to perform intracellular transport? In vertebrates and other higher animals, based on the structure of kinesin molecules, kinesin family members have been divided into 8 distinct classes, Group I to Group VIII (Hirokawa, 1996). Interestingly in C. elegans among the
klp-1 to
klp-20 genes, all structural types of kinesin proteins from Group I to Group VIII exist. Among these are genes that have been characterized previously such as
klp-3 (Khan et al., 1997),
osm-3 (Shakir et al., 1993; Tabish et al., 1995),
unc-104 (Otsuka et al., 1991; Hall and Hedgecock, 1991),
unc-116 (Patel et al., 1993; J. White, D. Hall, E. Hedgecock, D. Thierry-Mieg, and our unpublished data),
vab-8 (Wolf et al., 1998), and
zen-4 (Raich et al., C. elegans meeting,1997). We have begun a genetic analysis of interactions between various kinesins by constructing double mutants, gene knockouts and RNA injections to examine their phenes. RNA in situ hybridization data on whole mount embryos, using digioxiginine labeled cDNA probes from representative kinesins from all eight groups suggest that multiple kinesins co-express in early embryogenesis of C. elegans, in different cell lineages. These results provide a temporal and spatial expression pattern of the kinesin superfamily in a metazoan during early development. We thank D. Hall, N. Hirokawa, Y. Kohara, T. Motohashi, J. Miwa, K. Nisihikawa, D. T. Mieg, E. Hedgecock, R. Holmgren, and A. Otsuka, for support. Research funds were provided by the Minsitry of Education, Science, Sports and Culture, Japan and NEC Co., Japan to SSS.