Anemia and block in erythropoiesis is detected earlier in Egr1^+/−, Apc^del/+double heterozygous mice compared with Apc^del/+mice. (A) Peripheral blood counts of Apc^fl/+, Apc^del/+, and Apc^del/+, Egr1^+/− mice 3 months after induction. (B) Flow cytometric analysis of spleen cells isolated from mice, 3 months postinduction. Ter119^high cells were analyzed using the CD71 and FSC parameters. Ery.A (Ter119^highCD71^highFSC^high) are basophilic, and Ery.B (Ter119^highCD71^highFSC^low) are late basophilic and polychromatic, whereas Ery.C (Ter119^highCD71^lowFSC^low) are orthochromatic erythroblasts and reticulocytes. A representative plot is shown on the right. Data represents the relative erythroid populations and standard error of the mean for 3 mice for each genotype. (C) The frequency of apoptosis in the R2 (CD71⁺Ter119⁺) population was measured by Annexin V staining. A representative contour plot is shown on the right. Apc^del/+ and Egr1^+/−, Apc^del/+ mice consistently displayed a trend toward less apoptosis in the CD71⁺Ter119⁺ population compared with controls. For all experiments, the average and standard error of the mean of 3 mice per genotype is shown. HCT, hemocrit.