Molecular Characterization of Autosomal Recessive Chronic Granulomatous Disease Caused by a Defect of the Nicotinamide Adenine Dinucleotide Phosphate (Reduced Form) Oxidase Component p67-phox

Abstract

Chronic granulomatous disease (CGD) is a rare inherited disorder of phagocytes in which defective production of microbicidal oxidants leads to severe recurrent infections. CGD is caused by mutations in any of 4 genes encoding components of nicotinamide adenine dinucleotide phosphate (reduced form; NADPH) oxidase, the multisubunit enzyme that produces the precursor of these oxidants, superoxide. Approximately 5% of CGD patients have an autosomal recessive form of disease caused by a severe deficiency of p67-phox, a 526-amino acid subunit of the oxidase that appears to regulate electron transport within the enzyme. Here we report the biochemical and molecular characterization of 6 unrelated kindreds with p67-phox deficiency. These studies show that, as in gp91-phox and p22-phox deficiencies, the p67-phox CGD patients show a high degree of heterogeneity in the genetic defects that underlie their disease. Five different mutant alleles were identified: (1) a nonsense mutation in exon 4 (C304 → T); (2) a 5-nucleotide (nt) deletion in exon 13 (nts 1169-1173); (3) a splice mutation in the first nucleotide of intron 4 (G → A); (4) a deletion of 1 nt in exon 9 (A728); and (5) a 9-nt in-frame deletion in exon 2 (nts 55-63). The splice mutation was seen in 3 unrelated kindreds, while the 5-nt deletion was seen in 2 apparently unrelated families (both of Palestinian origin). Homozygosity was present in 4 of the kindreds, 2 of which had consanguineous parentage. In the isolated neutrophils of each of the affected patients in the 6 kindreds, there was no measurable respiratory burst activity and no p67-phox protein detected by immunoblot analysis. The level of 67-phox mRNA was less than 10% of normal in the mononuclear leukocytes from 3 of the 4 patients analyzed by Northern blot studies. Thus, this heterogeneous group of mutations in p67-phox all lead to marked instability of mRNA or protein (or both) that results in the complete loss of NADPH oxidase activity.

Alu-repeat-induced deletions within theNCF2gene causing p67-phox-deficient chronic granulomatous disease (CGD)

“…However, this DK58 variant was unable to bind Rac-GTP and to translocate to the membrane [Leusen et al, 1996]. For the amino-acid substitutions and small in-frame deletions described by others Patino et al, 1999], the lack or diminished levels of the protein may be a consequence of structural instability and increased susceptibility to intracellular proteases, similar to the case described in our work.…”

“…The genetic aberrations are family-specific and comprise a wide range of mutation types. Mutations are also family-specific in p22-phox [Yamada et al, 2000] and-as reported so far-in p67phox [Patino et al, 1999] deficiencies, which are much rarer than the X-linked form (each $5% of all CGD cases). In contrast, p47-phox deficiency ($25% of all CGD cases [Roesler et al, 2000]) is mostly due to recombination events between the NCF1 gene and one out of two highly homologous pseudogenes, thus leading to the same GT deletion at the beginning of exon 2 in $90% of all p47-phox-deficient CGD patients.…”

Four different NCF2 mutations in six families from Turkey and an overview of NCF2 gene mutations

“…4). This mutation was previously described in heterozygous form by Khan et al [23] and in homozygous form by Patino et al [24] and Wolach et al [11].…”

Advances in primary immunodeficiency diseases in Latin America: epidemiology, research, and perspectives

“…[24][25][26][27][28][29][30][31][32][33][34][35][36] Research groups from Argentina, Brazil, Colombia, Mexico, and Costa Rica have performed studies in some well-known PIDs, such as CGD, agammaglobulinemia, hyper-IgM syndrome, Wiskott-Aldrich syndrome, and ataxia-teleangiectasia, resulting in several publications that pointed to particular phenotypes and novel genotypes. [67][68][69][70][71][72][73][74][75][76] These studies have contributed new insights about PID clinical presentation and have had a positive impact on the molecular diagnosis of PIDs. Specifically, these studies have shown that BCG complications are prevalent among SCID, T cell deficiency, and CGD patients; that fungal infections are highly prevalent among X-linked hyper-IgM patients; and that ataxia-telangiectasia is exceptionally frequent in Mexico and Costa Rica.…”