The genes
unc-93,
sup-9, and
sup-10 are believed to encode subunits of a potassium channel responsible for the regulation of muscle contraction (de la Cruz, 1998 worm meeting). Altered function mutations in any one of these genes result in flaccid paralysis and a defect in egg-laying. Furthermore, null alleles of any one of these genes result in recessive suppression of paralysis and restoration of egg-laying ability induced by the gain-of-function alleles in either of the other two genes. One such gain-of-function allele,
unc-93 (
e1500), was used in an effort to test the efficacy of ENU (N-ethyl-N-nitrosurea) as a mutagen. Three novel suppressor alleles of
unc-93 (
e1500) were found during this process (DeStasio et al., 1997). Several characteristics of the novel suppressors indicated that, unlike other known suppressor alleles, these alleles were interacting with
unc-93 (
e1500) in a previously undiscovered suppression pattern. Animals homozygous for the suppressor allele and
unc-93 (
e1500) are fully suppressed but the new alleles are dominant suppressors of
e1500 heterozygotes and recessive suppressors of
e1500 homozygotes, suggesting a specific and stoichiometric protein-protein interaction with
unc-93 (
e1500). Finally, homozygous hermaphrodites have normal fecundity but males are incapable of mating and
e1500; sup-new heterozygous males mate only at very low frequency. All three suppressor alleles complement null alleles of
unc-93,
sup-9, and
sup-10. Two and three factor mapping experiments place the location of the suppressor alleles on chromosome II between -13 and -16, a position relatively close to
sup-9 on the genetic map (-11.91). Sequence analysis of
sup-9 in the three suppressed strains show a single missense mutation in predicted membrane spanning regions of
sup-9. All three mutations are the result of a T to G transversion mutation, substituting an arginine for a methionine in two alleles and an arginine for a leucine in the third allele. Currently we are analyzing several aspects of the novel
sup-9 mutations. RT-PCR is being used to confirm the presence of
sup-9 mRNA. Experiments indicate that the male mating deficiency found in these strains is due to a defect in the very early events in mating behavior. Finally, a possible interaction between
dpy-17 and the new
sup-9 mutations is being explored as are ineteractions with other
sup-9 alleles.