FIG. 1.

(A and B) Chromatid breaks following MMC (A) or HU (B) treatment occur at a greater frequency in splenocytes expressing Eμ-D1T286A. Splenocytes derived from nontransgenic or premalignant Eμ-D1T286A mice were cultured for 24 h in the presence of 100 μM MMC or cultured for 24 h, followed by a 2-h pulse with 2 mM HU and resuspension in fresh media. Cells were then treated with Colcemid for 2 h to allow arrest in metaphase. (C) Untreated nontransgenic and Eμ-D1T286A splenocytes do not exhibit a significant number of chromatid breaks. Representative images of metaphase spreads are shown, and the average number of chromatid breaks per metaphase spread was quantified for each treatment.