Worm Breeder's Gazette 3(2): 24
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.
The ability of a variety of compounds to induce visible mutants (unc, dpy, etc.) has been tested. The list of compounds includes the following: ICR-191, ICR-364, proflavin, 2-nitrofluorene, 9- isothiocyanato-acridine, irehdiamine A, nitrosoguanidine (NG) and diethyl sulfate (DES). DES is a very effective mutagen, while NG and ICR-191 are weakly mutagenic. The other compounds listed were not mutagenic even at saturating concentrations or when the animals were grown for a generation in the presence of the compound. Nitrosofluorene induced some phenocopies but no true-breeding mutants. The possibility that the gut or the cuticle might not be permeable to some of these agents was recognized, so mutagenesis was also attempted in the presence of DMSO or Tween 80. These agents did not seem to enhance mutagenesis by any of the compounds tested, but it was interesting to find that C. elegans grows almost normally in 0.5% DMSO or in 1% Tween 80. (However, worms will not reproduce in liquid medium containing 5% DMSO.) The best treatment found for NG mutagenesis was suspension of the animals for one hour in pH 6.0 buffer containing 0.5 mg/ml NG. This concentration of mutagen is 10-fold higher than that used for bacteria. Visible mutants were detected at a frequency of about 1%; about 10- fold less frequent than is found with the standard EMS treatment. At lower concentrations of NG, mutagenesis is less efficient, while higher concentrations substantially decrease fertility. The acridine derivitive, ICR-191, was mutagenic when the animals were grown in 0.1 mg/ml ICR for a generation. Again, this concentration is 10-fold higher than that used for efficient bacterial mutagenesis, but the nematodes thrive on it. They seem to accumulate the compound in their gut to produce a bright yellow coloration, but neither fertility nor growth rate are greatly affected. David Baillie and I collected 50 ICR-induced visible mutants. They occur at the relatively low frequency of 0.2%. Most of the mutants fell into complementation groups previously defined by EMS-induced mutants. However, three new genes were detected in this study: dpy-4 (IV) has two ICR-induced alleles, him-4(X) has two ICR-induced alleles, and let- 13(I) has one allele. With these exceptions the spectrum of ICR- induced mutants does not differ from the spectrum of EMS-induced mutants. EMS was tested for its ability to induce reversion of ten of the ICR-induced mutants. Three of the ten were induced to revert at a closely-linked site by EMS. This suggests that ICR-191 and EMS may induce similar types of mutations in C. elegans.In contrast to the above compounds, DES (Aldrich Chemical Co.) is an extremely effective mutagen. Foreward mutation frequencies comparable to those obtained with EMS are achieved when using 0.01 M DES. In this procedure, 5 l DES are dissolved in 2 ml M9 buffer and added to a 2 ml suspension of worms for 2 hours at 20 C. Under these conditions, the spectrum of mutants induced to revert by DES is as yet indistinguishable from that of EMS. Also, similar numbers of revertants are obtained with these two mutagens. Thus, the only advantages of DES are that less is used for a shorter time. DES carries a warning label: skin irritant!