Mosaicism of an ELANE mutation in an asymptomatic mother in a familial case of cyclic neutropenia.
OBJECTIVE
To confirm and characterize mosaicism of the cyclic neutropenia (CyN)-related mutation in the ELANE gene identified in the asymptomatic mother of patients with CyN.


METHODS
We identified sibling cases with CyN due to a novel heterozygous splicing site mutation, IVS4 +5SD G>T, in the ELANE gene, resulting in an internal in-frame deletion of 30 nucleotides (corresponding to a ten amino acid deletion, V161-F170). The mutated allele was also detected in their asymptomatic mother but at low frequency. We measured the frequency of the mutant allele from peripheral blood leukocytes (PBLs) by subcloning, and confirmed the allelic frequency of mosaicism in various cell types by massively parallel DNA sequencing (MPS) analysis.


RESULTS
In the subcloning analysis, the mutant allele was identified in 21.36 % of PBLs from the asymptomatic mother, compared with 54.72 % of PBLs from the CyN patient. In the MPS analysis, the mutant allele was observed in approximately 30 % of mononuclear cells, CD3(+) T cells, CD14(+) monocytes and the buccal mucosa. Conversely, it was detected in low frequency in polymorphonuclear leukocytes (PLMLs) (3-4 %) and CD16(+) granulocytes (2-3 %).


CONCLUSIONS
Mosaicism of the ELANE mutation has only previously been identified in one confirmed and one unconfirmed case of SCN. This is the first report of mosaicism of the ELANE mutation in a case of CyN. The MPS results suggest that this de novo mutation occurred during the two-cell stage of embryogenesis. PLMLs expressing the ELANE mutation were found to be actively undergoing apoptosis.
Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
Osamu
O
Hirata
Satoshi
S
Okada
Miyuki
M
Tsumura
Shuhei
S
Karakawa
Itaru
I
Matsumura
Yujiro
Y
Kimura
Toshiro
T
Maihara
Shin'ichiro
S
Yasunaga
Yoshihiro
Y
Takihara
Osamu
O
Ohara
Masao
M
Kobayashi
D000328:Adult; D058070:Asymptomatic Diseases; D047108:Embryonic Development / Q000235:genetics; D005260:Female; D005787:Gene Frequency; D006801:Humans; D019272:Leukocyte Elastase / Q000235:genetics*; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008297:Male; D009000:Monocytes / Q000502:physiology*; D009030:Mosaicism; D009035:Mothers; D009297:Nasal Mucosa / Q000502:physiology; D009503:Neutropenia / Q000175:diagnosis* / Q000235:genetics; D010375:Pedigree; D017384:Sequence Deletion / Q000235:genetics*; D035781:Siblings; D013601:T-Lymphocytes / Q000502:physiology*
D018950:Lipopolysaccharide Receptors; D019272:Leukocyte Elastase