Aberrant expression of neutrophil and macrophage-related genes in a murine model for human neutrophil-specific granule deficiency

Abstract

Neutrophil-specific granule deficiency involves inheritance of germline mutations in the CCAAT/enhancer-binding protein epsilon (C/EBPE) gene. Humans and mice lacking active C/EBPepsilon suffer frequent bacterial infections as a result of functionally defective neutrophils and macrophages. We hypothesized that these defects reflected dysregulation of important immune response genes. To test this, gene expression differences of peritoneally derived neutrophils and macrophages from C/EBPepsilon-/- and wild-type mice were determined with DNA microarrays. Of 283 genes, 146 known genes and 21 expressed sequence tags (ESTs) were down-regulated, and 85 known genes and 31 ESTs were up-regulated in the C/EBP-/- mice. These included genes involved in cell adhesion/chemotaxis, cytoskeletal organization, signal transduction, and immune/inflammatory responses. The cytokines CC chemokine ligand 4, CXC chemokine ligand 2, and interleukin (IL)-6, as well as cytokine receptors IL-8RB and granulocyte-colony stimulating factor, were down-regulated. Chromatin immunoprecipitation analysis identified binding of C/EBPepsilon to their promoter regions. Increased expression for lipid metabolism genes apolipoprotein E (APOE), scavenger receptor class B-1, sorting protein-related receptor containing low-density lipoprotein receptor class A repeat 1, and APOC2 in the C/EBPepsilon-/- mice correlated with reduced total cholesterol levels in these mice before and after maintenance on a high-fat diet. Also, C/EBPepsilon-deficient macrophages showed a reduced capacity to accumulate lipids. In summary, dysregulation of numerous, novel C/EBPepsilon target genes impairs innate immune response and possibly other important biological processes mediated by neutrophils and macrophages.

Transcriptional control of granulocyte and monocyte development

“…C/EBPe(À/À) mice develop all of the hematopoietic lineages, but have a defect in terminal neutrophil maturation resembling human cases of secondary granule deficiency (SGD; Yamanaka et al, 1997;Chumakov et al, 1997), and human cases of SGD harboring C/EBPe point mutations have been described (Lekstrom-Himes et al, 1999;Gombart et al, 2001). Defects in macrophage function are also present in C/EBPe(À/À) mice (Gombart et al, 2005). C/EBPa binds the promoter of micro-RNA 223, which in turn suppresses translation of nuclear factor I-A to favor granulocytic maturation (Fazi et al, 2005).…”

C/EBPε mediates nicotinamide-enhanced clearance of Staphylococcus aureus in mice

“…In particular, LTF and CAMP have been shown to exhibit anti-S. aureus activity (20)(21)(22). In addition, murine and human monocytes/macrophages with impaired expression of C/EBPε display signs of immaturity, impaired phagocytosis, and altered myelomonocytic-specific gene expression (8,13,16,17).…”

“…Recently, we and others have established the essential role of the myeloid-specific transcription factor CCAAT/enhancer-binding protein ε (C/EBPε) in the terminal differentiation as well as the functional maturation of neutrophils and monocytes/macrophages (10)(11)(12)(13)(14)(15)(16)(17). Neutrophils from C/EBPε-deficient mice (Cebpe -/-mice) display aberrant phagocytosis, respiratory burst, and bactericidal activities.…”

Acetylation of C/EBPε is a prerequisite for terminal neutrophil differentiation

“…[14][15][16] C/EBPe deficiency, demonstrated in knockout murine models, resembles the clinical phenotype of patients with neutrophil-specific granule deficiency, characterized by an increase in circulating immature neutrophils and recurrent pyogenic infections. 12,[17][18][19] As a result of differential RNA splicing and alternative translational start sites, human-C/EBPe is expressed as 4 protein isoforms (32,30,27, and 14 kDa) that represent functionally different roles during myeloid differentiation. These functional differences, transcriptional activation by C/EBPe 32/30 , transcriptional repression by C/EBPe 27 , and dominant negative regulation by C/EBPe 14 , can, at least partly, be explained by analysis of the functional domains of human-C/EBPe.…”