title: Childhood asthma and spirometric indices are associated with polymorphic markers of two vitamin D 25-hydroxylase genes.
abstract: BACKGROUND
  Polymorphic markers of vitamin D pathway genes have been associated with asthma traits in different White populations. This study investigated the relationship between asthma phenotypes and single nucleotide polymorphisms (SNPs) of vitamin D receptor (VDR), vitamin D binding protein (GC), two 25-hydroxylases (CYP2R1 and CYP27A1), and 1α-hydroxylase (CYP27B1) in Hong Kong Chinese children.
  
  
  METHODS
  23 SNPs of the five vitamin D pathway genes were successfully genotyped in 914 asthmatic children and 1231 non-allergic controls. Genotypic and haplotypic associations with asthma phenotypes (diagnosis, spirometric indices, total IgE, and eosinophil percentage) were analyzed by multivariate regression. Generalized multifactor dimensionality reduction was used to detect epistatic interactions between SNPs for asthma phenotypes.
  
  
  RESULTS
  Several SNPs of CYP27A1, CYP27B1, GC, and CYP2R1 were associated with asthma or spirometric indices, although only the association between FEV1 and CYP2R1 rs7935792 passed Bonferroni correction (p = 2.73 × 10(-4) ). Patients with CC genotype of rs7935792 had higher FEV1 than those with the other two genotypes. Asthma was also associated with TT haplotype of CYP27A1 and AGGATA haplotype of CYP2R1 (p = 0.021 and 0.024, respectively). Besides, strong association was found between FEV1 and GATAG of CYP2R1 (β = 13.37, p = 4.83 × 10(-4) ). GMDR failed to identify any 2-locus to 4-locus interaction that modulated asthma or spirometric indices.
  
  
  CONCLUSIONS
  Several SNPs and haplotypes of CYP2R1 are associated with asthma diagnosis and FEV1 in children. Asthma is also modestly associated with a CYP27A1 haplotype. These two 25-hydroxylase genes may be genetic determinants for asthma phenotypes in children.
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Ting Fan
authors.initials: TF
authors.lastname: Leung
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Susan Shuxin
authors.initials: SS
authors.lastname: Wang
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Man Fung
authors.initials: MF
authors.lastname: Tang
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Alice Pik-Shan
authors.initials: AP
authors.lastname: Kong
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Hing Yee
authors.initials: HY
authors.lastname: Sy
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Kam Lun
authors.initials: KL
authors.lastname: Hon
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Juliana Chung-ngor
authors.initials: JC
authors.lastname: Chan
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: Gary Wing-kin
authors.initials: GW
authors.lastname: Wong
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics; D000293:Adolescent; D000704:Analysis of Variance; D001249:Asthma / Q000235:genetics*; D016022:Case-Control Studies; D002648:Child; D053493:Cholestanetriol 26-Monooxygenase / Q000235:genetics*; D000072467:Cytochrome P450 Family 2; D005260:Female; D005819:Genetic Markers / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006723:Hong Kong; D006801:Humans; D008297:Male; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D018167:Receptors, Calcitriol / Q000235:genetics; D013147:Spirometry; D014807:Vitamin D / Q000235:genetics; D014809:Vitamin D-Binding Protein / Q000235:genetics
chemical_list: D005819:Genetic Markers; D018167:Receptors, Calcitriol; D014809:Vitamin D-Binding Protein; D014807:Vitamin D; D000072467:Cytochrome P450 Family 2; C506833:CYP2R1 protein, human; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; C000600378:CYP27B1 protein, human
keywords: 25-hydroxylase; asthma; single nucleotide polymorphism; spirometry; vitamin D