Worm Breeder's Gazette 16(2): 42
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
|1||Laboratory of Molecular Biology, Department of Ecological Engineering,, Toyohashi University of Technology, Tempaku-cho, Toyohashi 441-8580, Japan|
|2||Department of Pharmacology, University of Illinois, M/C 867, Chicago, IL-60607, USA|
To understand the genetic and cellular basis of kinesin motor function, we have previously identified the entire super-family of genes (klp-1 to klp-20), encoding kinesin-like proteins in C. elegans (Khan et al. 1997). Later, we have characterized cDNA clones corresponding to different kinesins in C. elegans. Based on the motor domain homology, we have determined the phylogenetic tree of kinesins using a computer based program, and defined nine different classes of kinesin motors in C. elegans. These nine classes of the nematode kinesins represent all major types of kinesins found across highly divergent organisms such as human, mouse, and Drosophila, etc. To determine the in vivo function of all nine groups of kinesins, we have used the techniques of mRNA in situ hybridization in embryos and germ lines, lacZ reporter gene assay, immuno-cytochemistry, and the RNA interference assay. For example, we cloned three novel C-terminal motor kinesins klp-15, klp-16 and klp-17 in C. elegans, orthologs of Drosophila NCD, involved in the chromosomal segregation. Phylogenetic and secondary structure analysis suggest that KLP-15, KLP-16, and KLP-17 constitute a unique subgroup, distinct from the NCD sub-family, whereas another C-terminal C.elegans kinesin like protein KLP-3 which is involved in chromosomal movement, groups with NCD (Khan et al., 1997). Double stranded RNA interference assay suggests that all four klps (klp-3, klp-15, klp-16 and klp-17) facilitate chromosomal movement and spindle orientation at different developmental stages (Ali et al.,1999). The klp-17 transcripts appear to be highly localized in the cell nucleus (Ali and Siddiqui, 1999). In contrast, the klp-15 expresses in the cytoplasm of cells found in the periphery of embryos. Likewise, the klp-16 expression is uniform in 1-cell to 8-cell stage, but later expression is localized in the anterior region of the embryo. These data suggest that the different C-terminal motors play unique roles during embryogenesis. Similarly, our observations suggest that N-terminus motor KLP-7 (ortholog of MCAK) KLP-12 (ortholog of chicken Chromokinesin), KLP-14 (ortholog of BimC) are involved in chromosomal segregation. Our studies on C. elegans kinesin and previously known information suggest that out of twenty kinesin proteins, at least nine kinesins be involved in chromosomal movement. Thus, we propose that a large battery of kinesins mediate chromosomal segregation. These motors function in a combination of unique and overlapping manner, suggesting a complex hierarchy of kinesin motor function in metazoans.