The Association Between ADAM33 Polymorphisms Of T2 And S2 Locuses And Asthma

BackgroundBronchial asthma(Asthma) is a complex disease being of inclination of inheritance obviously,which is characterized of family assemble.The development and the progress of asthma is determined by the interaction of the genetic susceptibility and environmental factors.At present there were a large amount of studies about asthma,researchers had applied themselves diligently to the studies of the inheritance etiology of asthma.Up to now there had been lots of studies tried to investigate the susceptible gene of the asthma susceptible patients.They hoped to find the asthma susceptible gene to help to realize the pathogeny of asthma,meanwhile,it was a way to provide clues for the effective treatment of asthma.ADAM33(A disintegrin and metalloproteinase) SNPs(singlenucleotide polymorphisms) as a hotspot had been studied much for several years.Initially,ADAM33 was found at cell membrances,which was a metalloproteinase anchored at membrances.Because they had the disintegrate structural domain and the metalloproteinase structural domain these two domains,a disintegrin and metalloproteinase was named[1].SNPs were kinds of polymorphisms of DNA sequences caused by dissociation at nnucleotides,incluing convertion,reversal,deletion and insertion of single base.Since 2002 Van Eerdewegh et al[2]published their identification of ADAM33 as an asthma susceptible gene by a genomewide scan for 460 white sib-pairs from the United States and the UK.They demonstrated highly significant linkage for asthma and airway hyperresponsiveness(AHR) in the region of chromosome 20p13.By linkage disequilibrum studies with 135 SNPs of 23 genes in this region,they found higher LD between ADAM33 and adjacent genes,24 SNPs in three genes were significant with asthma and AHR.The majority of the these SNPs(14)were in ADAM33 and located in the 3'region of the gene.So they indentified ADAM33 gene as the susceptible gene for asthma and AHR.In the light of the genetics,heredity was of the character of race specificity.The distribution of the same SNP was diverse in the different races of people,and the influence was not alike.Now there were lots of researchers investigated the association between ADAM33 SNPs and asthma susceptibility,severity,lung function and allergy using case-control,haplotype analysis and transmission disequilibrium test and so on.And the conclusion were also different.Until now there was't a study yet which can conclude one SNP was associated with all races.The specific function of ADAM33 are unknown yet,but it is supposed that ADAM33 is associated with AHR and air remodeling according to the selective expression in the interstitial cell[2],the change of activity would lead to the abnormal function of the airway smooth muscle cell and fibroblast necessarily.ObjectivesADAM33 was identified as a susceptibility gene related to asthma and AHR.After that researchers from different countries did a great deal of studies among different populations,the conclusions were inconsistent.There are 179 SNPs in ADAM33 gene,25 are located in coding region(5 are homonymy,25 are inhomonymy).The studies about ADAM33 SNPs and Chinese asthma patients of Han people are less,so our objective is to find the relation between ADAM33 SNPs and Chinese asthma patients of Han people by PCR—direct sequencing and case-control analysis.MethordsAccording to the guide formulated by Chinese Medical Association we recruited 186 asthma patients dignosed in clinic and 150 healthy individuals random.All subjects came from Nan Fang Hospital and consented this research.In the asthma group,there were 95 men and 91 women,the averge age was 47.78 years old.In the control group,there were 78 men and 72 women,the averge age was 41.92 years old.There were 71 asthma patients who had been tested the lung function.159 patients had a allergic rhinitis,whose EOS of peripheral blood were increasing.All of the healthy controls did not have the asthmatic symdrome,like wheezing,breathless,long time chronic cough and so on.The two groups were both Chinese Han people and there was not a significant difference between the age and the gender in two groups.Genomic DNA in blood cell from venous blood was abstracted by reagent box.Selected T2 and S2 locuses and analysed them by PCR—direct sequencing in two groups.Distributions of T2 and S2 locuses alleles and the frequencies of the alleles were compared between the two groups using X2 test.The severity of asthma between two groups were compared using nonparametric Test.Lung functions during genotypes were compared by Fisher's Exact Test.Odds ratios and 95%confidence intervals were caculated for each genotype using logistic regression models.All of the caculations were put out by SPSS13.0.P(0.05 was significant.Results1.Age between asthmatic group and the control group was compared by t test,t=0.486,P=0.627(tab 1),there was not a significant difference between the age of the two group.2.Gender between asthmatic group and the control group was compared by X2 test,X2=0.028,P=0..866(tab 2),there was not a significant difference between the gender of the two group.3.The distribution of the genotype CC,CT,TT ofT2 locus of ADAM33 in asthmatic group were 139,47,0 respectively.Caculated X2 by the formula of Hardy-weinberg equilibrium test,X2=3.74,P＞0.05,the distribution of T2 locus's genotypes were in line with Hardy-weinberg equilibrium test.Caculated X2 of S2 locus by the same way,X2=2.01,P＞0.05,the distribution of S2 locus's genotypes were in line with Hardy-weinberg equilibrium test.In the control group, Caculated X2 of two locuses according to the same formula,X2 were 0.998 and 1.43 respectively,P＞0.05,both of the two locuses were in line with Hardy-weinberg equilibrium test.4.We did not test the TT genotype for the T2 locus,the major reason maybe because of the small sample.The allele frequence of T of T2 locus were 12.6%and 7.6%in cases and controls,respectly.The allele frequence of C of S2 locus were 24.8%and 16.3%in cases and controls,respectly.There was a significant difference in the genotype distributions of T2 and S2 locuses between two groups(T2:P=0.026,S2:P=0.021),the two locuses were related to the susceptibility of asthma.5.We classified the cases as mild,moderate and severe based on the asthma symptoms and the lung functions.The genotype distributions of T2 and S2 locuses among three groups were of no significant differences (T2:P=0.897,S2:P=0.811),which meant that T2 and S2 SNPs were of no relations with asthma severity.6.We caculated the comparative criticality between the two groups using logistic regression models.The odds ratios were 1.867 and 0.444,respectively.The rare allele could significantly increase the danger of asthma. (T2:P=0.027,S2:P=0.024)7.We divided cases into EOS(+)and EOS(--) according to the blood cell sorts and the usage of the drugs.There was no significant difference between the genotypes distribution of the two locuses and EOS,which meant that T2 and S2 SNPs were of no relations with allergy.(T2:P=0.128,S2:P=0.111)8.Caculated the relations between genotypes and lung function(FEV1%,FEV1/FVC,FVC%) by Fisher's Exact Test,P of T2 locus were 0.432,0.546 and 0.538.P of S2 locus were 0.640,0.427 and 0.738.There was not a significant difference between the lung function and genotypes of the two locuses.ConclusionThere were significant differences between the T2 and S2 locuses in ADAM33 and the susceptibility of the Chinese Han asthma.The rare allele can significantly increase the danger of asthma,but there was no association regarding ADAM33 and allergy and lung function decrease.The role of polymorphisms in ADAM33 gene to pathogenesis of asthma will be clarified by studying larger number of samples and analyzing more SNPs.