ETHYLNITROSOUREA-INDUCED MUTATIONS INVIVO INVOLVING THE DOLICHOS-BIFLORUS AGGLUTININ RECEPTOR IN MOUSE INTESTINAL EPITHELIUM

A mutagenesis assay system in introduced based on the induction of mutations in somatic cells of mouse small intestine using ethylnitrosourea (ENU). F1 mice, heterozygous for the Dolichos bifloru agglutinin (DBA) locus (Dlb-1a/Dlb-1b) encoding the DBA cell surface receptor, were treated in utero on either day 7, day 9 or day 11 post coitum. Mutant intestinal cell population of adult mice were visualised in whole-mount preparations by the absence of histochemical statining using peroxidase-labelled Dolichos biflorus agglutinin. Loss of staining is attributed to mutagenesis of the Dlb-1b allele in the heterozygote. This system allows one to evaluate mammalian mutagenesis in vivo at a single locus. Mutant cell populations appeared as discrete groups of 'stripers villi, each stripe comprising cells derived from unstained crypt stem cells (cf. Schmidt et al., 1985a). A spontaneous mutation level was noted in untreated controls which was found to differe significantly from the recorded in mice treated with the mutagen (P < 0.01). The mutation scores were hihgly consistent among mice and a small number of animals (i.e., 16) were sufficient to detect mutagenic effects of ENU. Thus, the advantages which accure from the assay are (1) the ability to detect small clones of mutant cell population in the intestine (i.e, cells derived from a single mutate crypt); (2) a small number of tested mice are required to generate a conclusive result, especially when compared to the mammalian spot test (Fahrig, 1978). © 1990.