unc-55 encodes a transcription factor that is a member of the nuclear receptor gene family.
unc-55 mutant males are unable to mate successfully. The relatively mild defect in coordination is unlikely to be responsible for the defect in male-mating behavior. Using an
unc-55::gfp transgenic strain, gfp expression was observed in one neuron, a muscle and the four spicule sheath cells in the male tail. The spicule sheath cells, which normally have a dumb-bell shape, are stretched when the spicules are extended. The pattern of expression in
unc-55 mutant males was indistinguishable from wild-type males. Observation of
unc-55 mutant male behavior revealed that males exhibit normal chemotaxis in locating hermaphrodites, move backward along the body of hermaphrodites and make appropriate turns but mutants do not copulate. Further observation of
unc-55 males revealed that often the paired spicules are extended in the absence of hermaphrodites, this is rarely observed in wild-type males. One approach that we are using to investigate the relationship between the cells expressing
unc-55::gfp and the control of spicules during copulation is to identify target genes regulated by UNC-55, a putative transcription factor. We compared the mRNA populations of two
him-5 strains, one homozygous for
unc-55(+) and the second homozygous for
unc-55 (
e1170) using Representational Differentiation Analysis. We have sequenced 48 different clones representing 36 different cDNAs. The transcription of each of the cDNAs appeared to be activated by UNC-55. Attempts to identify cDNAs suppressed by UNC-55 did not yield any products. The cDNAs fell into five categories: muscle specific (4), cytoskeletal (5), protein synthesis (9) signal transduction (5) and novel (4). The remaining represented flanking fragments of products that had already been identified. Reverse northern blots will be used to confirm the differential expression of the mRNAs in the two populations. We are encouraged by the correlation between the cell types, the potential function in copulation and the categories of genes that are potentionally regulated either directly or indirectly by UNC-55 in those cell types.