Mice expressing a neutrophil elastase mutation derived from patients with severe congenital neutropenia have normal granulopoiesis

Abstract

Severe congenital neutropenia (SCN) is a syndrome characterized by an isolated block in granulocytic differentiation and an increased risk of developing acute myeloid leukemia (AML). Recent studies have demonstrated that the majority of patients with SCN and cyclic neutropenia, a related disorder characterized by periodic oscillations in the number of circulating neutrophils, have heterozygous germline mutations in the ELA2 gene encoding neutrophil elastase (NE). To test the hypothesis that these mutations are causative for SCN, we generated transgenic mice carrying a targeted mutation of their Ela2 gene ("V72M") reproducing a mutation found in 2 unrelated patients with SCN, one of whom developed AML. Expression of mutant NE mRNA and enzymatically active protein was confirmed. Mice heterozygous and homozygous for the V72M allele have normal numbers of circulating neutrophils, and no accumulation of myeloid precursors in the bone marrow was observed. Serial blood analysis found no evidence of cycling in any of the major hematopoietic lineages. Rates of apoptosis following cytokine deprivation were similar in wild-type and mutant neutrophils, as were the frequency and cytokine responsiveness of myeloid progenitors. The stress granulopoiesis response, as measured by neutrophil recovery after cyclophosphamide-induced myelosuppression, was normal. To define the leukemogenic potential of V72M NE, a tumor watch was established.

Cyclic neutropenia in mammals

“…Nonetheless, one should not overlook the fact that different species have different metabolic rates, and dynamics proceed with characteristic species' time scales that follow allometric principles [12]. Therefore, and in keeping with this discussion, the conclusion that mutations in ELA2 alone cannot explain CN in a mouse model must be interpreted with caution [13]. Measuring the neutrophil count ev-ery week in mice proves unfortunate, as such a sampling period turns out to be a multiple of the CN cycling period.…”

Polymorphisms in the promoter region of neutrophil elastase gene and lung cancer risk

“…This mature 218 amino acid glycoprotein has a critical pathophysiolocial role in a variety of pulmonary disease, including lung cancer [11]. Recently, several studies reported association between mutations in the NE gene and two rare genetic diseases, cyclic neutropenia and severe congenital neutropenia [12][13][14][15][16][17][18][19]. There are 25 single nucleotide polymorphisms (SNPs) listed in the National Center for Biotechnology Information (NCBI)/SNP database (November 10, 2004), 13 of them are validated.…”

Expression of the secondary granule proteins major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX) is required for eosinophilopoiesis in mice

“…In addition, it is noteworthy that knock-in mice with single ELA2 mutations found in patients do not result in a baseline neutropenia in these animals. 42,43 This implies that effects on multiple granule proteins may be required for this effect in neutrophils. However, to date we have not been able to show that the engineered MBP-1 and EPX loci 16,17 actually generate truncated or aberrant polypeptides (our unpublished observations) and the suggestion that specific events need to coordinately happen in two genes limits the probability of this explanation.…”