ABSTRACT
In this paper, we report for the first time the results of an investigation on the association of signal transducer and activator of transcription 6 (STAT6) with asthma in the Indian population. A novel polymorphic CA-repeat in the proximal promoter region [R1] and a previously identified CA-repeat in the 5'-untranslated region [R3] were genotyped, and haplotypes [R1_R3] were generated using PHASE software. The 16 repeat allele at the R1 locus was positively associated (P = 0.01) with asthma. The 15 and 16 repeat alleles at the R3 locus were positively (P < 10(-4)) and negatively (P < 10(-5)) associated with asthma, respectively. Further, the 17_15 (P = 0.0031) and 16_15 (P = 0.001) haplotypes were found to be positively associated with asthma, whereas 17_14, 24_16, and 23_16 were negatively associated (P < 10(-5)). It appears that the R3 and R1 loci together play a bigger role in asthma than either of them alone, and the R3 locus has a larger effect than the R1 locus. Although alleles at the R1 locus appeared to be associated with total serum immunoglobulin E level, the genotypes showed no association, and the R3 locus showed no effect. As no exonic variants of STAT6 are known as yet, repeat polymorphisms in the regulatory regions and their haplotypes could be important in deciphering the genetic role of STAT6 in asthma and atopy.
Subject(s)
Asthma/genetics , Haplotypes/genetics , Polymorphism, Genetic/genetics , Trans-Activators/genetics , Adult , Asthma/metabolism , DNA Mutational Analysis , DNA Repeat Expansion/genetics , Gene Expression Regulation/genetics , Gene Frequency/genetics , Genetic Testing , Genotype , Humans , Immunoglobulin E/blood , Immunoglobulin E/genetics , India , STAT6 Transcription Factor , Trans-Activators/metabolismABSTRACT
Epidemiologic studies in India show that the prevalence of asthma is increasing, but no genetic studies have been reported on the Indian population thus far. We selected the IFNG locus on 12q21 as a candidate gene for asthma on the basis of its role in pathophysiology and positive linkage demonstrated in other populations. The aim of this study was to investigate association of a CA-repeat marker in this gene with asthma and total serum IgE levels in the North Indian population. The repeat region was PCR-amplified from patients and control subjects and analyzed through use of GeneScan. The distributions of allele sizes were found to be significantly different between patients and control subjects (Kolmogorov-Smirnov test, P < 10(-6)). Alleles 10 and 11 were found to be overrepresented in individuals with asthma, whereas alleles 13 and 15 were less likely in asthmatic individuals. We found that the CA-repeat polymorphism in the IFNG gene was significantly associated with total serum IgE levels (ANOVA, P < 10(-4) for control subjects and P =.0036 for patients). Furthermore, a previously reported promoter polymorphism at the -333 base pair position was not detected in our population. This is the first report on the association of a candidate gene with asthma from the Indian subcontinent.
