Wt1 loss phenotype is influenced by the genetic background and rescues Flt3-ITD mutation impact on stem cell population. (A) Kaplan-Meier survival curves of Wt1^fl/+Flt3^m/m animals with a C57BL/6 (Bl6) or 129S1/SvImJ (129S) genetic background compared with Wt1^+/+Flt3^m/m (Bl6) controls (n = 5-7). (B) Kaplan-Meier survival curves of Wt1^fl/+Flt3^m/+ (129S1/SvImJ) mice compared with control littermates (n = 10). WBC (K/µL) counts (C) and proportion of Lin⁻ cells (D) in the SPL of Wt1^fl/+Flt3^m/+ (129S1/SvImJ) mice compared with control littermates (n = 10). (E) Percentages of LSK cells in the BM and the SPL of primary recipients transplanted with total BM cells from Wt1^+/+Flt3^m/+, Wt1^fl/+Flt3^m/+, or Wt1^fl/flFlt3^m/+ mice (n = 5). (F) Ratios of donor (CD45.2⁺) mature cells in the BM and SPL compartments of recipient mice transplanted with cells from control, Wt1^fl/+Flt3^m/+, or Wt1^fl/flFlt3^m/+ mice (n = 5). Data are mean ± standard error of the mean (C-F). *P < .05, **P < .01, ****P < .0001, Mantel-Cox test (A-B) or 2-way analysis of variance (C-F).