In Vivo Assay to Screen for Mutagens/Carcinogens in the Nematode C. Elegans

Abstract

An in vivo mutagenesis assay has been developed in Caenorhabditis elegans, a free-living soil nematode. The assay takes advantage of three unique properties of this animal: (1) a large population of animals can be grown for mutagenesis assay (>500,000); (2) the animal has a short generation time (3 days at 25° C); and (3) homozygous recessive mutants can be readily generated (the animal is normally hermaphroditic). We have isolated a series of mutant strains which are small in size relative to “wild- type,” and we have used these mutants as genetic markers to detect mutagenesis. The assay is the reversion of small animals to larger “wild-type” animals. Revertants can be readily counted because of the great difference in size. A filtering system which can detect rare revertants in a population of 500,000 has been developed. Mutagenized small animals are allowed to swim through a uniform nylon mesh; revertants—which are much larger than mutants—are trapped on top of the filter and are subsequently counted. Known mutagens benzo(a)pyrene, 2-anthramine, MMS, EMS, and acridine orange, as well as “blind” chemicals from the Research Triangle Institute were tested. Our assay system can detect microgram quantities of chemicals; and, so far, the test with this animal does not require the addition of special S-9 preparations for activation.