Growth factor independence-1 (Gfi-1) plays a role in mediating specific granule deficiency (SGD) in a patient lacking a gene-inactivating mutation in the C/EBPϵ gene

A Khanna-Gupta, H Sun, T Zibello, HM Lee, R Dahl… - Blood, 2007 - ashpublications.org
A Khanna-Gupta, H Sun, T Zibello, HM Lee, R Dahl, LA Boxer, N Berliner
Blood, 2007ashpublications.org
Neutrophil-specific granule deficiency (SGD) is a rare congenital disorder marked by
recurrent bacterial infections. Neutrophils from SGD patients lack secondary and tertiary
granules and their content proteins and lack normal neutrophil functions. Gene-inactivating
mutations in the C/EBPϵ gene have been identified in 2 SGD patients. Our studies on a third
SGD patient revealed a heterozygous mutation in the C/EBPϵ gene. However, we
demonstrate elevated levels of C/EBPϵ and PU. 1 proteins in the patient's peripheral blood …
Abstract
Neutrophil-specific granule deficiency (SGD) is a rare congenital disorder marked by recurrent bacterial infections. Neutrophils from SGD patients lack secondary and tertiary granules and their content proteins and lack normal neutrophil functions. Gene-inactivating mutations in the C/EBPϵ gene have been identified in 2 SGD patients. Our studies on a third SGD patient revealed a heterozygous mutation in the C/EBPϵ gene. However, we demonstrate elevated levels of C/EBPϵ and PU.1 proteins in the patient's peripheral blood neutrophils. The expression of the transcription factor growth factor independence-1 (Gfi-1), however, was found to be markedly reduced in our SGD patient despite the absence of an obvious mutation in this gene. This may explain the elevated levels of both C/EBPϵ and PU.1, which are targets of Gfi-1 transcriptional repression. We have generated a growth factor–dependent EML cell line from the bone marrow of Gfi-1+/− and Gfi-1+/+ mice as a model for Gfi-1–deficient SGD, and demonstrate that lower levels of Gfi-1 expression in the Gfi-1+/− EML cells is associated with reduced levels of secondary granule protein (SGP) gene expression. Furthermore, we demonstrate a positive role for Gfi-1 in SGP expression, in that Gfi-1 binds to and up-regulates the promoter of neutrophil collagenase (an SGP gene), in cooperation with wild-type but not with mutant C/EBPϵ. We hypothesize that decreased Gfi-1 levels in our SGD patient, together with the mutant C/EBPϵ, block SGP expression, thereby contributing to the underlying etiology of the disease in our patient.
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