Loss of 1 copy of Ctnnb1 is sufficient to prevent fatal macrocytic anemia in Apc^del/+ mice. (A) Kaplan-Meier survival curves for Apc^del/+ (A; n = 34), Apc^del/+, Ctnnb1^del/+ (AC; n = 11), Ctnnb1^del/+ (C; n = 6), and Apc^fl/+, Ctnnb1^fl/+ (Cre⁻; n = 8) control mice. The median survival of Apc^del/+ mice was 255 days (previously published by Stoddart et al²⁰ ); thus, the A and AC mice were not littermates in this figure. All other mouse cohorts, monitored monthly for the development of macrocytic anemia, survived until the end of the study (∼400 days) (B) RBC parameters from complete blood counts (CBCs) and spleen size. CBCs and spleen size for Apc^del/+ mice were measured at the time of sacrifice, and for the other 3 cohorts were measured at the end of the study (∼400 days). Circles represent 2 Apc^del/+, Ctnnb1^del/+ mice that displayed moderate anemia and splenomegaly at the end of the study, suggestive of the onset of MDS. (C) Representative flow cytometric analysis of erythroid (CD71⁺Ter119⁺) and B cells (CD19⁺IgM⁺) in spleen isolated from mice for each cohort. Shown is the average percentage of CD71⁺Ter119⁺ erythroblasts and CD19^loIgM⁺ (immature) and CD19^hiIgM⁺ (mature) B cells from at least 3 mice from each cohort. In contrast to Apc^del/+ mice, 9 of 11 Apc^del/+, Ctnnb1^del/+ mice (82%) had a normal distribution of erythroid cells and B cells in the spleen, similar to controls. Analysis of the 2 exceptional Apc^del/+, Ctnnb1^del/+ mice with splenomegaly and moderate anemia is shown in supplemental Table 2. MCV, mean corpuscular volume.