Thrombocytopenia of Cre-induced mice harboring the mutated NPM1 cDNA transgenic cassette. (A) Peripheral blood cell counts of Npm1-TCTG/WT;Cre⁺ (n = 9) and Npm1-TCTG/TCTG;Cre⁺ (n = 8) vs control mice (n = 9; including 3 Npm1-WT/WT;Cre⁺, 3 Npm1-TCTG/WT;Cre⁻, and 3 Npm1-TCTG/TCTG;Cre⁻ pIpC-treated mice). (B) Significantly decreased platelets number in peripheral blood of both heterozygous and homozygous conditional mice 1 month after pIpC injection. Results are shown as mean ± standard deviation (error bars) from 13 Npm1-TCTG/WT;Cre⁺ and 10 Npm1-TCTG/TCTG;Cre⁺ vs 25 control mice (including Npm1-WT/WT;Cre⁺ [n = 9], Npm1-TCTG/WT;Cre⁻ [n = 9], and Npm1-TCTG/TCTG;Cre⁻ [n = 7] pIpC-treated mice). (C) Enlarged platelet size in Npm1-TCTG/WT;Cre⁺ mice (N = 4) is shown as increased (i) mean platelet volume, (ii) platelet distribution width, and (iii) platelet-large cell ratio. (iv) Peripheral blood smears showing both the paucity of platelets and their substantially larger size (arrows) in heterozygous mutant mice vs littermate Cre⁻ pIpC-treated controls. *P < .05, **P < .01, ***P < .001 (unequal-variance t test).