title: Skewing of X-chromosome inactivation in three generations of carriers with X-linked chronic granulomatous disease within one family.
abstract: BACKGROUND
  Chronic granulomatous disease (CGD) is an inherited disorder of the innate immune system characterized by impairment of intracellular microbicidal activity of phagocytes. Mutations in one of the four known NADPH-oxidase components preclude generation of superoxide and related antimicrobial oxidants, leading to the phenotype of CGD. Defects in gp91-phox, encoded by CYBB, lead to X-linked CGD, responsible for approximately 70% of all CGD cases. The aim of the study was to evaluate the hypothesis that age-related skewing of X-chromosome inactivation, as described in several CGD families, is caused by preferential survival of bone marrow clones with an inactive NADPH oxidase.
  
  
  METHODS
  We studied the neutrophils from three patients and four carriers in three generations of a Turkish family with X-linked CGD. Carrier detection was carried out by the dihydrorhodamine (DHR)-1,2,3 assay, which measures on a per-cell basis the NADPH oxidase-dependent oxidation of DHR by phagocytes. The X-chromosome inactivation pattern was determined with the HUMARA assay in DNA from leucocytes as well as in DNA from a buccal smear of the four carriers.
  
  
  RESULTS
  The three patients were identified by a negative DHR test, and the mutation in their CYBB gene was characterized by DNA sequencing. Moreover, we found an age-related degree of skewing of X-chromosome inactivation in the leucocytes of the four X-CGD carriers, both at the protein level (NADPH oxidase activity) and at the DNA level (HUMARA assay). However, similar skewing of X-chromosome inactivation was found in the buccal DNA from these women.
  
  
  CONCLUSIONS
  These novel findings indicate that the age-related degree of skewing was probably a chance finding, not related to preferential survival of NADPH oxidase-deficient precursor cells, because this enzyme is not expressed in (buccal) epithelial cells.
authors.affiliation: Division of Pediatric Immunology, University of Hacettepe, Ankara, Turkey. kokyavuz@hotmail.com
authors.forename: M Y
authors.initials: MY
authors.lastname: Köker
authors.forename: O
authors.initials: O
authors.lastname: Sanal
authors.forename: M
authors.initials: M
authors.lastname: de Boer
authors.forename: I
authors.initials: I
authors.lastname: Tezcan
authors.forename: A
authors.initials: A
authors.lastname: Metin
authors.forename: C
authors.initials: C
authors.lastname: Tan
authors.forename: F
authors.initials: F
authors.lastname: Ersoy
authors.forename: D
authors.initials: D
authors.lastname: Roos
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D002353:Carrier State; D002610:Cheek; D002675:Child, Preschool; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006105:Granulomatous Disease, Chronic / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019255:NADPH Oxidases / Q000235:genetics; D009504:Neutrophils / Q000201:enzymology; D010375:Pedigree; D017354:Point Mutation; D011944:Receptors, Androgen / Q000378:metabolism; D014421:Turkey; D049951:X Chromosome Inactivation
chemical_list: D011944:Receptors, Androgen; D019255:NADPH Oxidases