Dysregulation of transcriptions in primary granule constituents during myeloid proliferation and differentiation in patients with severe congenital neutropenia

We examined the expression of granule constituent genes in myeloid progenitor cells during proliferation and differentiation in patients with severe congenital neutropenia (SCN). The heterozygous mutation of the neutrophil elastase gene was identified in two of four patients. The CD34⁺/granulocyte-colony stimulating factor receptor (G-CSFR)⁺ cells of SCN patients showed defective responsiveness to G-CSF in serum-deprived culture. The CD34⁺/G-CSFR⁺ cells expressed low levels of the granule constituent mRNAs. The transcription levels of primary granule enzyme genes in CD34⁺/G-CSFR⁺ cells were gradually enhanced and then decreased when cells were induced toward myeloid lineage with G-CSF in normal subjects. However, the primary up-regulation and the following down-regulation of these enzyme transcriptions were not clearly observed in SCN patients. No differences in expressions of the lactoferrin gene were seen between normal subjects and patients with SCN. We hypothesize that the abnormal regulation of the transcription in primary granule constituents might involve the defective proliferation and differentiation of myeloid cells in patients with SCN.