We have been conducting a search for new genes which affect sensitivity to volatile anesthetics. We previously showed that mutations in the genes
unc-79(
e1068 and
ec1) and
unc-80(
e1272) caused increases in sensitivity to one group of volatile anesthetics ( represented by halothane) but not to two others (represented by enflurane and isoflurane, respectively). We have started screens for mutations which alter sensitivity to isoflurane and enflurane (as well as new mutations altering the response to halothane). Our rationale is that if anesthetics decrease some neurologic function(s), then hypomorphic or loss of function mutations should cause increases in sensitivity. We have started screening at concentrations of anesthetics that are about 50% the concentration that immobilizes N2. At these concentrations N2 is uncoordinated but moving actively. Using these approaches we have identified several new mutations that increase sensitivity to enflurane or isoflurane. We were mildly surprised when five of these new mutations (four with increased sensitivity to isoflurane and one with increased sensitivity to enflurane) were new alleles of
unc-79 and
unc-80. One of the new alleles of
unc-79 appears not to have the increased sensitivities to halothane that
e1068 and
ec1 exhibit. (Gosh, sounds like an allelic series to me.) Interestingly, in three screens to find other EMS- induced mutations with increased sensitivities to halothane, we have not isolated any new alleles of either
unc-79 or
unc-80. Anyway, we will test each new allele in anesthetics from all four groups of anesthetics to try to make some sense of all this. If there really are serious allelic differences we plan to make the double heterozygotes to identify any interactions between the alleles. In addition, we have looked for new suppressors of the abnormal sensitivity of
unc-79 and
unc-80 to halothane. We previously identified the kinked mutants
unc-1(X),
unc-7(X) (thanks to David Miller),
unc-9(X) and
unc-24(IV) as suppressors of this phenotype of
unc-79 and
unc-80. Our screen is to EMS-mutagenize
unc-80 (or
unc-79) and look for moving F2's at 2% halothane. All the new suppressors we have isolated are X-linked kinked mutants. One of the new kinked alleles is particularly interesting since
unc-80 in turn suppresses its kinked phenotype. So far, we have found no strong suppressor of
unc-79 or
unc-80 which does not have the kinked phenotype. All this has led to an increased interest in the strong suppressor,
unc-1. We are actively screening for spontaneously arising
unc-1 mutations to begin a transposon tagging approach to cloning this gene. We are using three approaches for this. 1.) Brute force screening for kinky mutants. 2.) Screening for suppression of the
unc-79 phenotype in a strain containing
mut-6 and
ec1. 3.) Screening for loss of the coiler phenotype in a strain containing
mut-6 and the dominant coiler allele of
unc-1,
e1598.