Cbfβ is involved in maturation of all lineages of hematopoietic cells during embryogenesis except erythroid

The transcription factor Cbfβ forms a heterodimeric complex with members of the Runx family of proteins. Together, Cbfβ and Runx1 play a critical role in the establishment of definitive hematopoiesis in mouse embryos. Previously, we used a Cbfb-GFP “knock-in” mouse model to demonstrate that Cbfβ is expressed in hematopoietic stem cells of the mouse fetal liver and aorta-gonad-mesonephros (Blood 100 (2002), 2449). We also examined the expression pattern of Cbfβ in different lineages of adult hematopoietic cells and found that it is expressed uniformly in all lineages except B lymphocytes and erythroid cells. Cbfβ expression decreases during maturation of B cells in the adult bone marrow, and is not expressed in nucleated erythroid precursors. Here, we examine the expression of Cbfβ in various hematopoietic lineages, including myeloid, lymphoid, and erythroid during late stages of embryonic development, and compare it to the pattern observed in adults. We find that there are subtle differences in expression of Cbfβ-GFP in embryonic hematopoietic cells compared to their adult counterparts, but that the overall pattern is the same. Our data complement recently published data on hematopoetic defects observed in transgenic Cbfb-null mouse embryos partially rescued by ectopic expression of Cbfb (Nature Genet. 32 (2002), 633; Nature Genet. 32 (2002), 645). and supports the emerging view that Cbfβ and Runx proteins are required for normal maturation of hematopoietic cells as well as establishment of definitive hematopoiesis.