Kinesin is believed to generate force for the movement of organelles in anterograde axonal transport. In C. elegans,
unc-116 gene encodes the kinesin heavy chain (Patel et al., 1993). There is variation in the severity of phenotype among different alleles of the
unc-116 gene; mutant animals of the
rh24 allele ( E. Hedgecock ) are severely paralyzed,whereas those from
e2310 allele (J. Mancillas) have mild defect in locomotion, and coil up as larvae;
f130 allele (D. Thierry Mieg) is a larval lethal. The
unc-116 is a strict maternal effect gene has been shown by genetic tests (D. Hall, J. Plenefisch and E. Hedgecok, 1991; K. Naert and D. Thierry-Mieg, C. elegans meeting 1997). These data suggests that the KHC is stored in oocytes. Another interesting phenotype of the
unc-116(
rh24) mutants is the arrest of ealry embryos at first cleavage, and defects in spindle formation,and orientation (John White and Steven Hurd, personal communication and WBG, 1992; K. Naert and D. Thierry Mieg, C. elegans meeting 1997). They have observed defects in nuclear migration, and spindle formation. Similarly an interaction with
mei-1 gene has been shown (Paul E.Mains WBG, 13(3):23,1994). Due to the wealth of information on the
unc-116 mutant phenotypes, we have begun examining the
unc-116 expression in the wild type using
unc-116 reporter gene with lacZ (See the accompaanying abstract by Ali et al., this meeting). However, the lacZ expression vector does not express in early embryos and in the germ line,therefore, we have used the RNA in situ hybridization technique (Tabara et al, 1996)to visualize
unc-116 gene expression on whole mount embryos and animals using digioxigenic labeled
unc-116 cDNA probes. Our results suggest that there is no transcription of the khc gene in the one cell stage, or its is at a very low level. From the 2-cell stage onward, we have observed a strong signal in both AB and P1 blastomeres, and this heavy expression of the gene continues through the 4-cell, 8-cell, 16-cell, and 24-cell stages. The RNA signal can be observed in later embryos also, but it is slightly reduced in comparison to the early mitotic divisions. Thus, the
unc-116 expression is continuous from 2-cell stage until hatching during embryogenesis. We have also stained the dissected gonads from the wild type hermaphrodies and found intense
unc-116 RNA expression in the oocytes. During post-embryonic development, we have obserevd the
unc-116 signal in the head, body wall and the tail region throughout larval and adult stages. In particular, expression is seen in the nerve ring area, neurons in the first and terminal pharyngeal bulbs, ventral cord, and the tail ganglia. There is a weaker, but noticeable signal in the pharyngeal and bodywall muscle cells. These data are consistent with our large promoter
unc-116-L::lacZ expression in the lacZ fusion gene transgenic animals (See Ali et al., WCWM, 1998). We have begun experiments using various mutants that are affected in early embryonic development to see the expression of the
unc-116 encoded signal in different genetic background. Our data has shown that indeed
unc-116 is a maternally expressed gene and this expression is highly required in the first cell stage, as there is no de novo transcription of the khc gene in the one cell. We thank J. Mancillas, D. Hall, E. Hedgecock, J. Plenefisch, D. Theirry Mieg, K. Naert, J. White and S. Hurd for sharing unpublished results, and cooperation. We also thank the Ministry of Education, Science and Culture, Japan for providing research grants to S.S.S.