Mutational analysis of patients with p47-phox-deficient chronic granulomatous disease: The significance of recombination events between the p47-phox gene (NCF1) and its highly homologous pseudogenes

Objective. The aim of this study was to determine the molecular basis of p4 7-phox-deficient chronic granulomatous disease (CGD), the most common autos omal recessive form of the disease, CGD is an inherited condition character ized by defective oxygen radical production due to defects in the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, Mutational an alysis of p47-phox-deficient CGD patients previously demonstrated that the majority of patients have a GT dinucleotide (Delta GT) deletion at the star t of exon 2, a signature sequence also observed in the highly homologous ps eudogenes of NCF1, Materials and Methods. We performed genetic analysis of NCF1 and its pseudo genes using genomic DNA in 29 p47-phox-deficient CGD patients from 2 2 sepa rate families. First-strand cDNA analysis was performed in 17 of the 29 pat ients, Results, We confirmed the significance of the Delta GT mutation; in 27 of 2 9 patients, only the Delta GT sequence was detectable. All but one of the 2 7 had at least one additional signature sequence, specific to the pseudogen e, in either intron 1 and/or intron 2, We extended our analysis to look at signature sequence differences in exons 6 and 9 and detected both the wild- type and pseudogene sequences in all patients tested. Conclusions. Although detection of only Delta GT sequence accounts for over 85% of affected patients, the molecular basis is most likely due to partia l cross-over events between the wild-type and pseudogene(s) of p47-phox at different recombination sites, Our results suggest that complete gene conve rsion or deletion of the p47-phox gene (NCF1) occurs rarely, if it all. (C) 2001 International Society for Experimental Hematology. Published by Elsev ier Science Inc.