Fig. 1.

Derivation and phenotypic characterization of Kit-gatekeeper mice. (A) Targeting strategy for the simultaneous knock-in of V558Δ (exon 11) and T669I (exon 14) into the 129/Sv Kit locus. Blue and red bars denote the exons with the respective point mutations. A similar targeting vector with a shorter 3′ homology arm was used to generate the single-mutant Kit^V558Δ/+ mice (Fig. S1A). Triangles (not drawn to scale) indicate loxP sites; white gaps indicate BamHI restriction sites; bar indicates 518-bp Southern blot probe. DTA, diphtheria toxin A gene; NEO, neomycin resistance gene. (B) Kaplan–Meier survival plot showing increased survival of gatekeeper-mutant Kit^{V558Δ;T669I/+} mice in comparison with Kit^V558Δ/+ mice (n ≥ 43 each; ticks indicate censored subjects). (C) Photographs of ileocecal junctions showing reduced length and diameter of tumor alongside the cecum in Kit^{V558Δ;T669I/+} mice (Middle; red bracket indicates straight cecal GIST) in comparison with Kit^V558Δ/+ mice (Bottom; blue bracket indicates twisted cecal GIST). Of note, the cecum is significantly shorter in Kit^{V558∆;T669I/+} mice than in wild-type mice (Top; black arrow) and Kit^V558∆/+ mice. Representative pictures of 3-mo-old animals are shown with colon facing down left and ileum facing down right (n ≥ 59 each). (Scale bar, 1 cm.)