Erythropoiesis in mice inducibly ablated for Trim28. TMC [Trim28^flox/flox:Tg^Mx1Cre (flox/flox:Mx1Cre)] mutant or control [Trim28^flox/flox (flox/flox) and Trim28^flox/+:Tg^Mx1Cre (flox/+:Mx1Cre)] mice at ages 5 to 6 weeks were injected every 48 hours with poly(I:C) 5 times to transcriptionally activate the cre-expressing transgene.²⁶  Uninjected Trim28^flox/+ (flox/+) mice were used as controls. Mice were analyzed 2 weeks (2w) or 4 weeks (4w) after completion of poly(I:C) administration. (A) The absolute number of total bone marrow cells isolated from 2 femurs plus 2 tibias of individual animals (each circle) of various genotypes. The black bar represents the average. * indicates statistically significant, P < .05. NS: not significant, P > .05. (B) Flow cytometric analysis of erythropoiesis in total bone marrow cells from mutant and control mice. The numbers in each of the boxed areas indicate the mean frequency of cells in each hematopoietic population. (C) The abundance of Trim28 floxed allele in CD71⁺TER119⁺ immature erythroid cells was analyzed by qPCR. The CD71^hiTER119^- cells that aberrantly accumulated in the TMC mutant mice (panel B) were also analyzed. An average of the relative amount of the undeleted gene in the control Trim28^flox/flox cell was set to 200, which is the copy number of the floxed allele in 100 cells. (D) The expression level of β-type globin genes normalized to β-actin in CD71⁺TER119⁺ immature erythroid cells was analyzed by qRT-PCR. The average of the relative amount in the control Trim28^flox/flox cell was set to 1. (E) The absolute number of cells in each of the analyzed populations was calculated from the data shown in (A) and (B). Average with standard error of the mean (SEM). (F) Flow cytometric analysis of TER119⁺ cells in total bone marrow cells (separated by forward scatter and CD44 antigen according to Chen et al³⁴ ). The numbers closest to the boxed areas indicate the mean percentage of cells in each population within parental TER119⁺ cells. (G) The absolute number of basophilic erythroblasts (r2), polychromatic erythroblasts (r3), orthochromatic erythroblasts (r4a), reticulocytes (r4b), and RBCs (r5) in the bone marrow was calculated from the data shown in panels (A) and (F). Error bars represent the SEM. (H) Hematologic parameters of peripheral blood cells. Data represent either a summary (A,C,D,E,G,H) or representative individuals (B,F) of more than 3 mice of each genotype from 2 to 4 independent experiments.