C/EBP epsilon mediates myeloid differentiation and is regulated by the CCAAT displacement protein (CDP/cut)

Neutrophils from CCAAT enhancer binding protein epsilon (C/ EBP epsilon) kn ockout mice have morphological and biochemical features similar to those ob served in patients with an extremely rare congenital disorder called neutro phil-specific secondary granule deficiency (SGD), SCD is characterized by f requent bacterial infections attributed, in part, to the lack of neutrophil secondary granule proteins (SCP). A mutation that results in loss of funct ional C/EBP epsilon activity has recently been described in an SGD patient, and has been postulated to be the cause of the disease in this patient. We have previously demonstrated that overexpression of CCAAT displacement pro tein (CDP/cut), a highly conserved transcriptional repressor of development ally regulated genes, suppresses expression of SGP genes in 32Dcl3 cells. T his phenotype resembles that observed in both C/EBP epsilon-/- mice and in SGD patients. Based on these observations we investigated potential interac tions between C/EBP epsilon and CDP/cut during neutrophil maturation, In th is study, we demonstrate that inducible expression of C/EBP epsilon in 32Dc l3/tet cells results in granulocytic differentiation. Furthermore, Northern blot analysis of G-CSF-induced CDP/cut overexpressing 32Dc13 cells reveale d absence of C/EBP epsilon mRNA, We therefore hypothesize that C/EBP epsilo n positively regulates SCP gene expression, and that C/EBPe is itself negat ively regulated by CDP/cut during neutrophil maturation. We further demonst rate that the C/EBP epsilon promoter is regulated by CDP/cut during myeloid differentiation.