Ectopic Expression of CCAAT/Enhancer Binding Proteinβ(C/EBPβ) in Long-Term Bone Marrow Cultures Induces Granulopoiesis and Alters Stromal Cell Function

Abstract

CCAAT/enhancer binding proteins (C/EBP) have been demonstrated to impact directly the development of multiple hematopoietic lineages. However, the role of C/EBPbeta in the differentiation of various hematopoietic lineages has not been thoroughly examined. We used primary bone marrow cultures to assess directly the ability of C/EBPbeta to influence myelopoiesis. Retroviral expression vectors were used to express C/EBPbeta ectopically in murine primary long-term bone marrow cultures. The differentiation potential of these cells was determined using hematopoietic colony assays and differential staining of cells within the cultures. Bone marrow cultures that overexpressed C/EBPbeta had fewer myeloid progenitors and a significant increase in the number of granulocytes. The ability of C/EBPbeta to alter hematopoiesis in vitro was dependent on the presence of the transcriptional activation domain because LIP, which lacks this functional domain, did not decrease the ability of bone marrow cultures to support myeloid progenitors. These data also show that C/EBPbeta influences hematopoiesis by altering stromal cell function rather than the intrinsic developmental potential of myeloid progenitor cells.

C/EBPγ deregulation results in differentiation arrest in acute myeloid leukemia

“…It has previously been shown that ectopic expression of other C/EBP members, such as C/EBPα or C/EBPβ, can induce granulocytic differentiation of cell lines or primary cells in vitro (56)(57)(58)(59). In contrast, our experiments demonstrate that C/EBPγ overexpression, either induced by ectopic expression in cell culture or by excision of C/EBPα in KO mice, results in a block of neutrophilic differentiation.…”

FMIP controls the adipocyte lineage commitment of C2C12 cells by downmodulation of C/EBPalpha

“…The difference in the role of C/EBPalpha between the adipocyte system and granulocyte system is not clear. Interestingly, C/EBPalpha is required for adipocyte differentiation, whereas in the granulocyte differentiation system C/EBPalpha can be replaced by C/EBPbeta (Popernack et al, 2001;Jones et al, 2002;Wang and Friedman 2002). However, only a low level of C/EBPalpha is sufficient for granulocyte differentiation.…”

Ectopic expression of HOXC6 blocks myeloid differentiation and predisposes to malignant transformation

“…The enrichment of hematopoietic stem cell genes may explain the growth advantage observed in our experiments. In further Gene Set Enrichment Analysis (GSEAs) enrichment of target genes of the essential myeloid transcription factors PU.1, CEBPß and Runx1 (AML1) was identified (Figure 5 D-FF) [21]. No enrichment of the signature was detected between GMPs and CMPs, making a differentiation-induced phenomenon unlikely [21].…”