title: Evidence for an asthma risk locus on chromosome Xp: a replication linkage study.
abstract: BACKGROUND
  Asthma is a complex genetic disorder characterized by chronic inflammation in the airways. Identification of genetic risk factors for asthma has been complicated due to genetic heterogeneity and influence from environmental risk factors. Despite the fact that multiple genetic linkage studies have been carried out the results are still conflicting and call for replication experiments. A Danish genome-wide scan has prior reported evidence for candidate regions for asthma susceptibility genes on chromosomes 1p, 5q, 6p, 12q and Xp. Linkage to chromosome 12q was later confirmed in the same replication sample as used in the present study. The aim of the study was to replicate linkage to candidate regions for asthma in an independent Danish sample.
  
  
  METHODS
  We performed a replication study investigating linkage to candidate regions for asthma on chromosomes 1p36.31-p36.21, 5q15-q23.2, 6p24.3-p22.3, and Xp22.31-p11.4 using additional markers in an independent set of 136 Danish asthmatic sib pair families.
  
  
  RESULTS
  Nonparametric multipoint linkage analyses yielded suggestive evidence for linkage to asthma to chromosome Xp21.2 (MLS 2.92) but failed to replicate linkage to chromosomes 1p36.31-p36.21, 5q15-q23.2 and 6p24.3-p22.3.
  
  
  CONCLUSIONS
  The replication results provide evidence for chromosome Xp21 to harbour a susceptibility gene for asthma in the Danish population. To our knowledge, the study is the first to replicate evidence for linkage to chromosome X. A susceptibility gene for asthma on chromosome X could potentially explain observed gender differences in asthma prevalence.
authors.affiliation: Department of Biochemistry, Pharmacology and Genetics, Odense University Hospital, and Clinical Pharmacology, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Brasch-Andersen
authors.forename: M U
authors.initials: MU
authors.lastname: Møller
authors.forename: A
authors.initials: A
authors.lastname: Haagerup
authors.forename: J
authors.initials: J
authors.lastname: Vestbo
authors.forename: T A
authors.initials: TA
authors.lastname: Kruse
mesh_terms: D001249:Asthma / Q000235:genetics*; D002874:Chromosome Mapping; D041321:Chromosomes, Human, X / Q000235:genetics*; D005260:Female; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D012307:Risk Factors