EXCLUSIVE EXPRESSION OF C-ELEGANS OSM-3 KINESIN GENE IN CHEMOSENSORY NEURONS OPEN TO THE EXTERNAL ENVIRONMENT

In Caenorhabditis elegans three genetic loci osm-3, unc-104 and unc-11 6 have been identified, which encode anterograde motor kinesin. Here w e show that osm-3 encodes a 672 amino acid long kinesin-like protein ( KLP) that contains all three functional domains similar to the kinesin heavy chain, including a globular motor region, an alpha-helical coil ed-coil rod, and a globular tail region. OSM-3 shows homology in both the motor and rod domains with kinesins from divergent species such as mouse KIF3, and sea urchin KRP95, and also with the rod domains of se veral non-kinesin proteins, such as myosin, ezrin, outer membrane prot eins alpha precursor OMPA, yeast intracellular protein transport USO1, and the rat neurofilament NF-H. Temporal and spatial expression of th e osm-3::lacZ fusion gene during development is limited to an exclusiv e set of 26 chemosensory neurons whose dendritic endings are exposed t o the external environment, including six IL2 neurons of the inner lab ial sensilla, eight pairs of amphid neurons (ADE ADL, ASE, ASG, ASH, A SI, ASJ, ASK) in the head, and two pairs of phasmid neurons (PHA and P HB) in the tail. Our data are consistent with the known structural def ects in the amphid and phasmid sensilla in osm-3 mutants and also show the expression of the gene in IL2 neurons. Temporally, the gene is di fferentially expressed in all three types of chemosensory sensilla. Fu rther work on osm-3, unc-104 and unc-116 mutants should give insight i nto the in vivo functions of the kinesin family during C. elegans neur ogenesis.