Inflammatory reactions and severe neutropenia in mice lacking the transcriptional repressor Gfi1

Abstract

The transcriptional repressor Gfi1 is a nuclear zinc-finger protein expressed in T-cell precursors in the thymus and in activated mature T lymphocytes. Previous experiments have shown that Gfi1 is involved in T-cell lymphomagenesis and in the development of T-cell progenitors. Here we show that Gfi1 is also expressed outside the lymphoid system in granulocytes and activated macrophages, cells that mediate innate immunity (that is, non-specific immunity). We have generated Gfi1-deficient mice (Gfi1-/-) and show that these animals are severely neutropenic and accumulate immature monocytic cells in blood and bone marrow. Their myeloid precursor cells are unable to differentiate into granulocytes upon stimulation with granulocyte colony-stimulating factor (G-CSF) but can develop into mature macrophages. We found that Gfi1-/- macrophages produce enhanced levels of inflammatory cytokines, such as tumor necrosis factor (TNF), interleukin-10 (IL-10) and IL-1beta, when stimulated with bacterial lipopolysaccharide (LPS) and that Gfi1-/- mice succumb to low doses of this endotoxin that are tolerated by wildtype mice. We conclude that Gfi1 influences the differentiation of myeloid precursors into granulocytes or monocytes and acts in limiting the inflammatory immune response.

The zinc finger protein Gfi1 acts upstream of TNF to attenuate endotoxin‐mediated inflammatory responses in the lung

“…1c). The absence of granulocytes in lungs of Gfi1 -/-mice is in agreement with the severe neutropenia reported earlier for Gfi1 -/-mice [24,25].…”

“…Previously we have shown that treatment with otherwise sublethal doses of LPS kills Gfi1 -/-mice within 36 h [24]. Here we report that in this model it is predominantly the lungs that are affected, as might be expected since the lung is a shock organ in Gramnegative sepsis.…”

“…In AM it was LPS-inducible as previously described for bone marrow-derived macrophages [24], but in AEC, Gfi1 expression was constitutive and transiently down-regulated by LPS. We speculate that such a differential expression pattern may be beneficial for the host, since the functional role and the activities of AM and AEC in the immune response are quite different.…”

“…Gfi1 -/-mice were generated by homologous recombination in R1 embryonic stem cells as described [24]. All mice used in this study were healthy animals aged 4-9 wk, more than 20 generations backcrossed with C57BL/6 mice.…”

“…Gfi1 is a zinccoordinating protein that mainly acts as a transcriptional repressor by binding to cognates sites upstream of target gene promoters [20][21][22][23]. When Gfi1-deficient mice were challenged with low doses of LPS that do not affect wild-type (WT) animals, they quickly succumbed with symptoms of septic shock and died within 36 h [24]. While the pathophysiological and molecular basis for this exaggerated effect of LPS in the absence of Gfi1 is unknown, it was shown that LPS-stimulated macrophages from Gfi1 -/-mice produced higher amounts of pro-inflammatory cytokines than their WT counterparts, notably TNF and IL-1b [24].…”