Worm Breeder's Gazette 8(3): 90

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.

Spontaneous Levamisole-resistant Mutants in the Bergerac strain of C. elegans

J.A. Lewis, T. Malisch

With a view toward cloning levamisole receptor genes, we've been 
isolating spontaneous levamisole-resistant mutants of the Bergerac 
strain.  The ability to select for very rare mutational events by 
survival on 1 mM levamisole plates has made mutant isolation fairly 
easy.  We prepared selection plates according to our variation (
Genetics g5: 905, lg80) of the method originally described by Brenner (
Genetics 77: 71, 1974).  Each selection plate represents the screening 
of the F2 progeny of 30 Bergerac hermaphrodites grown at 20 C.  So far 
we've isolated 15 spontaneous levamisole-resistant mutants.  We find a 
spontaneous mutant on every fourth selection plate whereas for the 
Bristol strain only 1 spontaneous levamisole-resistant mutant was 
found on 48 selection plates.  The Bergerac spontaneous rate is thus 
about 10 times the Bristol rate for the levamisole resistance genes.  
Of the 15 Bergerac Mutants, 6 are in unc-38, 5 in unc-63, and 1 each 
in the unc-2g, would 
probably only show up as partially resistant mutants, which we did not 
screen for).  By ethyl methanesulfonate mutagenesis, unc-29 mutants 
are far more common (74 of 211 mutants) compared to unc-38 (44 of 211 
mutants).  Our results suggest that either unc-29 is hard to 
spontaneously mutate or that unc-38 and unc-63 are mutationally 'hot.' 
We are presently backcrossing the unc-38 and unc-63 mutants into a 
Bristol background to look for new Tc1-associated restriction 
fragments not present in either Bristol or the Bergerac strain.