Tumor onset in the intestinal tract of ApcMin/+/ Vash2-/- mice. A, Genomic DNA samples isolated from mouse tails were genotyped by PCR using primers that detect both WT and mutant alleles of ApcMin/+ or Vash2. B, Dissection micrographs of the small intestine from ApcMin/+ mice (left) and ApcMin/+/Vash2-/- mice (right) at 16 weeks of age. C, Polyp numbers in the small intestine in ApcMin/+ mice (open column) or ApcMin/+/Vash2-/- mice (closed column) at 16 weeks of age. **P < 0.01, n = 8. D, LacZ activity in ApcMin/+mice, ApcMin/+/Vash2+/- mice and ApcMin/+/Vash2-/- mice. Expression of LacZ was not seen in ApcMin/+ mice or in ApcMin/+/Vash2+/- mice. Note the marked LacZ expression in crypts (arrows) and tumor cells in ApcMin/+/Vash2-/- (arrowheads). Line, tumor area.