Significance Of T₁ Locus Allele Single Nucleotide Polymorphism(SNP) In Exon Domain 20 Of ADAM33 Gene In Patients With Asthma Disease

Study BackgroundA disintegrin and metalloproteinase33(ADAM33),a rencently discovered matrix metalloproteinase,is expressed in human lung fibroblasts and bronchial smooth muscle,and is suggested to play an important role in airway remodeling and bronchial hyperresponsiveness(BHR).Single nucleotide polymorphisms(SNPs)are the most common mutation patterns of ADAM33 gene in patients with asthma and in normal individuals.In a number of present investigations,the ADAM33 gene was identified as being significantly associated with asthma and BHR.It is worth to note that some of the significant SNPs which may be associated with asthma and BHR were primarily located in the 3'region of the gene,including the transmembrane domain,cytoplasmic domain and the 3'untranslated region.T₁ locus allele in exon domain 20 of ADAM33 gene is also included.Recent studies indicate,T₁ polymophic site is a T to C substitution,and it leads 764 amino acid changing from Methionine to Threonine and increasing susceptibility of asthma.Distribution frequency of the same SNP change in various race is different,and its effects on asthma are also distinct.At present,there is no report that SNPs in ADAM33 is associated with asthma and BHR in Han Nationality of Southern China.ObjectivesTo analyze the association of T₁ polymorphism with asthmatic subjects in Han Nationality of Southern China,we used polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP)and DNA sequencing etc.to determine the polymorphism of T₁ locus allele in ADAM33 gene in asthmatic patients and normal control,MethodsIndividuals in two groups were studied.The asthmatic group included 164 subjects with asthma(101 males,and 63 females).The normal control group included 112 healthy individuals(69 males,and 43 females).The differences in age and sexual distinction were not significant(P＞0.05).All human subjects come from Han Nationality of Southern China and consent this research.Genomic DNA in white blood cell from venous blood was abstracted by reagent box.T₁ locus allele in exon domain 20 of ADAM33 gene were analysed by polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP)in both groups.Distribution of T₁ locus genotypes and frequency of T₁ locus allele were compared between the two groups. The frequency of T1 lOCUS allele in Han Nationality of Southern China was also compared with that in UK,US,German,Korean.In asthmatic patients,FVC%Pred, FEV₁%Pred levels was compared in three genotypes.Results1.Age distinction was compared between asthmatic subjects and normal control,t=0.468,P＞0.05.2.Sexual distinction was compared between asthmatic subjects and normal control,P= 0.997(P＞0.05).3.The frequencies of genotype of TT,TC and CC were respectively 129,30 and 5 in asthmatic subjects,which were in good agreement with Hardy-Weinberg equilibrium.The frequencies of genotype of TT,TC and CC were respectively 102,7 and 3 in normal control,which were not agreement with Hardy-Weinberg equilibrium.4.T₁ locus SNP exists in the healthy Han Nationality of Southern China Distribution of T₁ locus genotypes were TT 91.1%(102),TC 6.3%(7)and CC2.7%(3), respectively.5.No significant difference was found in T₁ locus allele frequency among UK,US,German,Korean and Southern China(x²=6.769,P＞0.05).6.There was a significant difference in the distributions of the genotypes(TT, TC,CC)between asthmatic subjects and normal control(x²=8.456,P＜0.05).Also, significant difference was observed in T₁ locus allele frequency between the two groups(x²=6.265,P＜0.05).7.The presence of C allele of ADAM33 gene was found to be a greater risk factor in asthmatic subjects than in normal control.The odds ratio(OR)of TC and TC +CC were 3.389(1.430～8.030),2.767(1.308～5.854),respectively,when compared with TT genotype,the P＜0.05.8.There was a significant decrease in the FVC%Pred,FEV₁%Pred levels of CC genotype compared with that of TT genotype.Conclusions1.The frequencies of the genotypes(TT,TC,CC)were in good agreement with Hardy-Weinberg equilibrium in asthmatic subjects,but not in normal control.2.T₁ locus SNP exists in Han Nationality of Southern China.3.No significant difference was found in T₁ locus allele frequency among UK, US,German,Korean and Southern China.4.T₁ polymophic site is associated with susceptibility of asthma in Han Nationality of Southern China.The T allele may be protective,while the C allele may be susceptibility gene for asthma.5.The potential mechanism of asthma caused by T₁ locus SNP:to cause decrease in the FVC%Pred,FEVl%Pred levels and to lead to increasing susceptibility of asthma.