Worm Breeder's Gazette 11(4): 79

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.

Anesthetics Just Put Me to Sleep

Shanta Sabnis, Susan Thomas, Phil Morgan and Margaret Sedensky

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.