Acetone, methyl ethyl ketone, ethyl acetate, acetonitrile and other polar aprotic solvents are strong inducers of aneuploidy in Saccharomyces cerevisiae.

A diploid yeast strain D61.M was used to study induction of mitotic chromosomal malsegregation, mitotic recombination and point mutation. Several ketones (including acetone and methyl ethyl ketone) and some organic acid esters (including the methyl, ethyl and 2-methoxyethyl esters of acetic acid) and acetonitrile strongly induced aneuploidy but not recombination or point mutation. Only diethyl ketone induced low levels of recombination and point mutation in addition to aneuploidy. Related compounds were weak inducers of aneuploidy: methyl n-propyl ketone, the methyl esters of propionic and butyric acid, acetic acid esters of n- and iso-propanol and ethyl propionate. No mutagenicity was found with n-butyl and isoamyl acetate, ethyl formate, acetyl acetone (2,5-dipentanone) and dioxane. Methyl isopropyl ketone induced only some recombination and point mutation but no aneuploidy. Efficient induction was only observed with a treatment protocol in which growing cells were exposed to the chemicals during a growth period of 4 h at 28 degrees C followed by incubation in ice for more than 90 min, usually overnight for 16-17 h. Aneuploid cells could be detected in such cultures during a subsequent incubation at growth temperature if the chemical was still present. Detailed analysis showed that there was a high incidence of multiple events of chromosomal malsegregation. It is proposed that the mutagenic agents act directly on tubulin during growth so that labile microtubules are formed which dissociate in the cold. When cells are brought back to temperatures above the level critical for reassembly of tubulin and allowed to grow, faulty microtubules are formed.