The
unc-104 gene is of interest because of its phenotypic effects on presynaptic vesicle localization, synaptic architecture, and neuromuscular junctions [Hall, D. and Hedgecock, E., Cell , in press]. The
unc-104 product is required in many, if not all, neurons for proper chemical synapse formation. The
unc-104 gene is capable of encoding a kinesin-related protein [Otsuka et al., Neuron, 6, 113-122 ( 1991) ] . Comparison of the presumed UNC-104 'motor' domain to other kinesinrelated proteins indicates a closer relationship to squid and Drosophila kinesin than to the kinesin family members involved in chromosome movement or nuclear functions (ncd, RAR3,
cut7, bimC, and nod) . At the time of its identif ication, the possibility existed that the UNC-104 protein was the nematode homolog of kinesin. However, the differences between kinesin and UNC-104 in the rod and tail region, and the discovery that
unc-116 encodes a protein with greater similarity to kinesin [Patel, N. and Mancillas, J. R., WBG, 11(4), 68 ( 1990) ] suggests that the
unc-104 product is a novel kinesin family member. Preliminary studies, which are now being expanded, revealed hybridization of an
unc-104 non-motor domain probe to mouse and human DNA. These preliminary results suggest the intriguing possibility that
unc-104-1ike genes are present in vertebrates. Studies of
unc-104- related proteins in vertebrates and of kinesin-related proteins in the nematode provide considerable promise of increasing our understanding of subcellular transport. Toward this end, studies have been undertaken to characterize the kinesin-related genes in C. elegans and the
unc-104-related genes in different organisms.