The CYBB gene (OMIM # 300481), which encodes gp91phox, localizes to the short arm of chromosome X at Xp21.1 [48]. Functional analysis of its transcriptional regulation has demonstrated multiple overlapping positive regulatory elements and repressors in the proximal 5′ flanking region [18, 49–51] as well as more distant 5′ regulatory elements [52]. Current literature includes 1156 unrelated kindreds with 1259 patients, and

a total of 621 different mutations, of which 368 mutations (59.3%) are unique for an individual kindred [23]. Molecular defects leading to X-linked CGD have been BTK inhibitor library identified in the coding region, introns, and (rarely) in the 5′ flanking regulatory regions of the CYBB gene [23]. Molecular changes include deletions Temsirolimus cell line (21.1%), insertions (6.6%), deletion/insertion (1.6%), nonsense (28.6%), missense (21.7%), splice site (19.7%) and regulatory region mutations (0.7%). The mutations are distributed

in a similar frequency among the exons and gene boundaries, with no preferential mechanisms or loci [23, 24, 53, 54]. Protein expression phenotypes of X-linked CGD have been classified as X91°, X91− and X91+, where the superscript denotes whether the level of gp91phox protein is undetectable, diminished or normal, respectively [55]. Among patients in whom gp91phox expression was determined by immunoblot or spectral analysis, protein levels were undetectable (X91°) in 82%, diminished (X91−) in 12% and normal (X91+) in 6% [23]. The CYBA gene (OMIM # 608508) encodes p22phox, also known as the alpha subunit or light chain of cytochrome b558 [56, 57]. Several heterogeneous mutations have been identified, and they are widely distributed throughout the gene [44]. Unlike the

heterogeneous mutations that lead to other forms of CGD, most of the autosomal defects in the NCF1 gene (OMIM # 608512) that encodes p47phox have been attributed to a single mechanism. In 35 independent patients with p47phox deficiency, the same deletion of two nucleotides was Erastin manufacturer identified in a GTGT repeat, corresponding to the first four bases of exon 2 of the NCF1 gene encoding p47phox [58, 59]. Currently, more than 300 patients described with this type of deletion [44]. This common mutation probably derives from recombination events between the NCF1 gene and an adjacent pseudogene, NCF1B, with the GT deletion [60]. A second pseudogene, NCF1C [61], shows greater homology to the functional gene, but its role in NCF1 mutation is unknown. Patients with mutations in the NCF1 gene have more benign clinical course compared to other CGD forms [22, 62]. A type II, not functional NCF1 pseudogene that presents the same sequence GTGT of the NCF1 functional gene has also been identified [63]. Mutations in the NCF2 gene that encodes p67phox (OMIM # 608515) include missense and nonsense mutations, substitutions at splice sites, a dinucleotide insertion and a variety of deletions [44, 64]. Nunoi et al.