Single nucleotide polymorphism screening and association analysis--exclusion of integrin beta 7 and vitamin D receptor (chromosome 12q) as candidate genes for asthma.
BACKGROUND
The human genes coding for integrin beta 7 (ITGB7) and vitamin D receptor (VDR) are two of the several candidate genes for asthma and related phenotypes found in a promising candidate region on chromosome 12q that has been identified in multiple genomewide screens and candidate gene approaches.


METHODS
All exons, including parts of the neighbouring introns, and the predicted promoter region of the ITGB7 gene were screened for common polymorphisms in 32 independent asthmatic and healthy probands, resulting in the detection of two single nucleotide polymorphisms (SNPs) unknown so far. In addition to these SNPs, five already described SNPs of the ITGB7 and one in the human VDR gene were analysed in a Caucasian sib pair study of 176 families with at least two affected children, using matrix assisted laser desorption/ionization time of flight mass spectrometry. All confirmed SNPs were tested for linkage/association with asthma and related traits (total serum IgE level, eosinophil cell count and slope of the dose-response curve after bronchial challenge).


RESULTS
Two new variations in the ITGB7 gene were identified. The coding SNP in exon 4 causes a substitution of the amino acid GLU by VAL, whereas the other variation is non-coding (intron 3). None of the eight analysed SNPs, of either the ITGB7 or the VDR genes, showed significant linkage/association with asthma or related phenotypes in the family study.


CONCLUSIONS
These findings indicate that neither the human ITGB7 nor the VDR gene seem to be associated with the pathogenesis of asthma or the expression of related allergic phenotypes such as eosinophilia and changes in total IgE level.
Vollmert
C
C
Institute of Epidemiology, GSF-National Research Center for Environment and Health, 85764 Neuherberg, Germany. vollmert@gsf.de
Illig
T
T
Altmüller
J
J
Klugbauer
S
S
Loesgen
S
S
Dumitrescu
L
L
Wjst
M
M
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000235:genetics*; D002648:Child; D002881:Chromosomes, Human, Pair 12; D005260:Female; D020869:Gene Expression Profiling; D005838:Genotype; D006801:Humans; D039641:Integrin beta Chains / Q000235:genetics*; D015810:Linkage Disequilibrium; D008297:Male; D020641:Polymorphism, Single Nucleotide; D018167:Receptors, Calcitriol / Q000235:genetics*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D039641:Integrin beta Chains; D018167:Receptors, Calcitriol; C091368:integrin beta7