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

Abstract

Neutrophils from CCAAT enhancer binding protein epsilon (C͞ EBP) knockout mice have morphological and biochemical features similar to those observed in patients with an extremely rare congenital disorder called neutrophil-specific secondary granule deficiency (SGD). SGD is characterized by frequent bacterial infections attributed, in part, to the lack of neutrophil secondary granule proteins (SGP). A mutation that results in loss of functional C͞EBP 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 protein (CDP͞cut), a highly conserved transcriptional repressor of developmentally regulated genes, suppresses expression of SGP genes in 32Dcl3 cells. This phenotype resembles that observed in both C͞EBP؊͞؊ mice and in SGD patients. Based on these observations we investigated potential interactions between C͞EBP and CDP͞cut during neutrophil maturation. In this study, we demonstrate that inducible expression of C͞EBP in 32Dcl3͞tet cells results in granulocytic differentiation. Furthermore, Northern blot analysis of G-CSF-induced CDP͞cut overexpressing 32Dcl3 cells revealed absence of C͞EBP mRNA. We therefore hypothesize that C͞EBP positively regulates SGP gene expression, and that C͞EBP is itself negatively regulated by CDP͞cut during neutrophil maturation. We further demonstrate that the C͞EBP promoter is regulated by CDP͞cut during myeloid differentiation.

Transcriptional control of granulocyte and monocyte development

“…Diminution of CDP DNA-binding during granulocyte maturation and its ability to repress the gp91-phox promoter suggests that downmodulation of CDP is required for terminal neutrophil differentiation (Skalnik et al, 1991). 32Dcl3 cells expressing exogenous CDP do not express C/EBPe or secondary granule proteins in G-CSF (Lawson et al, 1998;Khanna-Gupta et al, 2001). Consistent with the need to downmodulate CDP for terminal granulopoiesis, mice transgenically expressing CDP from the MMTV LTR develop a myeloproliferative disease with increased neutrophils infiltrating marrow and spleen (Cadieux et al, 2006).…”

Transcriptional regulation of granulocyte and monocyte development

“…The mechanism whereby CDP DNA-binding becomes inactivated during granulopoiesis remains to be elucidated. 32D cl3 cells overexpressing CDP do not express C/EBPe in response to G-CSF, and the human C/EBPe promoter contains a binding site for CDP at 71472 bp which potentially accounts for the reduced activity of an 1800 bp compared to a 726 bp promoter fragment in 32Dwt18 cells (Khanna-Gupta et al, 2001). Inhibition of C/EBPe expression may account for the combined loss of LF, neutrophil collagenase, and neutrophil gelatinase in 32D cells expressing exogenous CDP (Lawson et al, 1998).…”

Gene Expression Profiling during All-trans Retinoic Acid-Induced Cell Differentiation of Acute Promyelocytic Leukemia Cells

“…Critical to terminal granulocytic differentiation are the transcription factors PU.1, CCAAT/enhancer binding protein(C/EBP), core-binding factors (CBFs), and homeobox proteins. 44,45 We closely examined several transcriptional factors affected by ATRA treatment. After cells were exposed to ATRA, there was no change in the expression of CBF-␤ and C/EBP-␥.…”