Induction of C/EBPα activity alters gene expression and differentiation of human CD34+ cells

Abstract

The CCAAT/enhancer binding protein alpha (C/EBPα) belongs to a family of transcription factors that are involved in the differentiation process of numerous tissues, including the liver and hematopoietic cells. C/EBPα−/− mice show a block in hematopoietic differentiation, with an accumulation of myeloblasts and an absence of mature granulocytes, whereas expression of C/EBPα in leukemia cell lines leads to granulocytic differentiation. Recently, dominant-negative mutations in the C/EBPα gene and down-regulation of C/EBPα by AML1-ETO, an AML associated fusion protein, have been identified in acute myelogenous leukemia (AML). To better understand the role of C/EBPα in the lineage commitment and differentiation of hematopoietic progenitors, we transduced primary human CD34+ cells with a retroviral construct that expresses the C/EBPα cDNA fused in-frame with the estrogen receptor ligand-binding domain. Induction of C/EBPα function in primary human CD34+ cells, by the addition of β-estradiol, leads to granulocytic differentiation and inhibits erythrocyte differentiation. Using Affymetrix (Santa Clara, CA) oligonucleotide arrays we have identified C/EBPα target genes in primary human hematopoietic cells, including granulocyte-specific genes that are involved in hematopoietic differentiation and inhibitor ofdifferentiation 1 (Id1), a transcriptional repressor known to interfere with erythrocyte differentiation. Given the known differences in murine and human promoter regulatory sequences, this inducible system allows the identification of transcription factor target genes in a physiologic, human hematopoietic progenitor cell background.