The Association Of SERPINE2Gene With COPD In A Chinese Han Population

BackgroundChronic obstructive pulmonary disease (COPD) is characterized by irreversible and progressive bronchial obstruction and persistent airway inflammation. It is a common, complex disease that causes severe morbidity and mortality. It is the fourth leading cause of death in the world,and it's prevalence and mortality are expected to be increased in the coming decades. Therefore, a clear understanding of the various aspects of susceptibility to this lung disease is necessary in order to develop better treatments. So far, cigarette smoking has been proven the most important risk factor for COPD. Alpha1-antitrypsin (AAT) deficiency is another proven genetic risk factor for COPD. However, only15%of smokers have this disease and AAT deficiency is present in only1-2%of COPD cases. Furthermore, nonsmokers may also develop chronic airflow obstruction. All of these data suggest that genetic constitution as well as living habits play a role in the development and severity of COPD.Several studies have suggested that other genetic factors may also be involved in the patheogensis of COPD. Polymorphisms of several candidate genes have been studied and associated with the development of COPD.One such candidate is the SERPINE2[Serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type1), member2] gene. Genetic associa-tions with COPD-related traits can help to define distinct subtypes of COPD.SERPINE2is located on chromosome2q33-35. Using gene-expression microarray and animal model experiments, DeMeo and colleagues identified SERPINE2as a novel COPD-susceptibility gene. Zhu and colleagues also con-firmed the association between SERPINE2and COPD in a large case-control collection from Bergen, Norway, which included973cases with COPD and956control subjects.However, Chappell and colleagues'prospective study of1,018COPD cases and911controls coming from six European centers suggested that there was no significant association between SERPINE2and COPD. In order to clarify these contradictory results of SERPINE2in COPD, we conducted a case-control association study of three known single nucleotide polymorphisms (SNPs) of the SERPINE2gene in the Chinese population.ObjectiveUsing case-control study, we intend to determine the association between the three SNPs in SERPINE2and COPD in the Chinese Han population. The three SNPs in this study were rs840088G/A in intron1, rs1438831A/G in5'upstream sequence, and rs3795879G/A in intron3. Their polymorphisms in the409patients with COPD and the411unrelated controls obtained from a Chinese Han population were analyzed.Methods1. participants:All study subjects involved in this investigation were recruit-ed upon giving informed consent. The study design was approved by the ethical committee of Shandong University. This prospective observational study involved409patients with clinical diagnosis of COPD and411unrelated healthy controls without any respiratory system diseases. These820selected participants were of the Chinese Han population. All the patients and case-controls were recruited from Qilu Hospital and the Second Affiliated Hospital of Shandong University of Traditional Chinese Medicine. The average ages of the COPD patients and case-controls were65.1years and63.7years, respectively.The group of COPD were consisted of251men and158women,and219people had smoking history; The controls were consisted of266men and145women,and223people had smoking history.2. Collecting blood samples and extracting DNA:Collect blood samples from COPD patients and healthy controls in the Chinese Han population and then extract DNA from the white blood cells in peripheral blood using a standardized method. The DNA concentration and purity of each sample were analyzed by ul-traviolet spectrophotometry. All DNA samples were stored at-20℃until analysis.3. Genotyping:SNPs rs840088G/A,rs1438831A/G and rs3795879G/A of SERPINE2gene were detected by polymerase chain reaction (PCR) based restriction fragment length polymorphism (RFLP) technique in COPD subjects and healthy controls.4. Evaluate each polymorphism for Hardy-Weinberg equilibrium (HWE):using chi-square test and make sure all the genotypic and allele results were at Hardy-Weinberg equilibrium in both COPD patients and healthy controls used in the study.5. DNA sequencing:Direct sequencing of a subgroup of samples with the same primers was used to further validate the authenticity of genotype analysis. Sequencing was performed using the BigDye Terminator v1.1Cycle Sequencing kit (Applied Biosystems), and analyzed on an ABI PRISM3100DNA sequencer (Applied Biosystems, Foster City, CA, USA).6. Comparing the distribution of different genotypes and alleles of every polymorphism in the two groups:Compare the distribution of different genotypes and alleles of every polymorphism in the two groups by chi-square test to determine whether the polymorphisms were associated with COPD.Results1. The frequencies of genotypes AA, AG, GG at polymorphism sites rs840088A/G were13.9%,51.6%and34.5%respectively in COPD group, while16.3%,49.6%, and和34.1%in control group. Besides, the A type allele frequencies were0.397and0.412in patients and controls respectively, and the G type allele frequencies were0.603and0.588in COPD patients and healthy controls. There was no significant difference in genotype frequencies (P value=0.630) or allele frequencies (P value=0.567).2. The frequencies of genotypes AA, AG, GG at polymorphism sites rs1438831A/G, were2.9%,34.7%and62.4%respectively in COPD group, while4.9%,30.6%and64.5%in control group. Besides, the A type allele frequencies were0.203and0.202in patients and controls respectively, and the G type allele frequencies were0.797and0.798in COPD patients and healthy controls. There was no significant difference in genotype frequencies (P value=0.208) or allele frequencies (P value=0.960).3. For rs3795879, the frequency of homozygote AA genotype was75.6%in COPD and72.5%in the controls. The frequency of homozygote AG was22.7%in COPD and24.6%in the controls, and the frequency of homozygote GG genotype was1.7%in the cases and2.9%in controls. Besides, the A type allele frequencies were0.869and0.848in patients and controls respectively, and the G type allele frequencies were0.131and0.152in COPD patients and healthy controls. There was no significant difference in genotype frequencies (P value=0.398) or allele frequencies (P value=0.217).Conclusions No significant association was found between SNPs rs840088G/A, rs1438831A/G and rs3795879G/A polymorphism in SERPINE2and COPD susceptibility in Chinese Han population.