TRIM28 is essential for erythroblast differentiation in the mouse

We discovered that Trim28 genetic loss in the adult mouse leads to defective immature erythropoiesis in the bone marrow and consequently to anemia.We further found that TRIM28 controls erythropoiesis in a cell-autonomous manner by inducibly deleting Trim28 exclusively in hematopoietic cells. Finally, in the absence of TRIM28 we observed increased apoptosis as well as diminished expression of multiple erythroid transcription factors and heme biosynthetic enzymes in immature erythroid cells. Thus, TRIM28 is essential for the cell-autonomous development of immature erythroblasts in the bone marrow. To induce Cre recombinase from the Mx1Cre transgene, poly(I:C) was injected 5 times every other day. Mice were analyzed two weeks after completion of poly(I:C) administration. TRIM28 mutant mice generate two distinct types of immature erythroid cells; KOa, with 5-8% of the Trim28 gene remaining undeleted (still bearing 26% of residual mRNA), and KOb, with 1-4% of the gene remaining undeleted (and with 18% of mRNA remaining).