Association And Methylation Analysis Of 13 Candidate Genes In Nicotine Addiction With Men In Shanxi Province Of China

Nicotine dependence as an addictive disorder not only affects people’s behavior,but also increases the risk of various diseases,such as lung cancer,oral cancer,laryngeal cancer,cardiovascular and cerebrovascular diseases,and respiratory diseases etc.Because many countries and people gradually realized the catastrophic consequences of smoking,numerous regulations and laws against tobacco smoking have been implemented and developing of the effective smoking cessation drugs has becomea hot topic.Since smoking addiction is a complex disorder,which is regulated by environmental factors,genetic factors and epi-genetics factors,the pathogenesis of smoking addiction is less clear.In addition,the susceptibility genes for smoking addiction detected in genetic studies were mainly based on the samples with European and Africa origins.Therefore,performing the multi-omic analyses to find out the the biological mechanism of nicotine addiction for Chinese Han population,and to develop the precise smoking cessation drugs,has becomemore and more important.In this study,according to the former published results,we performed an multi-omics analysis with 13 genes from the nicotinic acetylcholine receptor family,dopamine receptor family,and serotonin in a Chinese Han population.The specific genetic architecture of nicotine dependence for Chinese Han population will be the foundation for the development of the effective cessation drugs.(1)Genetic and epigenetic analysis revealing the genetic mechanisms in the nAChRs with smoking:Nicotine dependence(ND)is a worldwide health problem.Numerous genetic studies have demonstrated a significant association of variants in nicotinic acetylcholine receptors(nAChRs)with smoking behaviors.However,most of these studies enrolled only subjects of European or African ancestry.In this study,we performed both association,interaction analysis,cis-mQTL analysis and differential methylation regions analysis for 67 SNPs in CHRNA3-A5,CHRNA7,CHRNB2,and CHRNB4 with ND in a Chinese Han population(N = 5,055)to find the potential biological mechanism of nicotine dependent.We revealed three novel SNPs in CHRNA3 and CHRNB4 to be significantly associated with the FTND score.Further,we showed that these significant variants contribute to ND via two methylated sites,and we demonstrated significant interaction affecting ND among variants in CHRNA5/A3/B4,CHRNA7,and CHRNA4/B2/A5.In sum,these findings provide robust evidence that SNPs in nAChR genes convey a risk of ND in the Chinese Han population.(2)Genetic and epigenetic analysis revealing the genetic mechanisms in the NCAM1–TTC12–ANKK1–DRD2 cluster with smoking:Although studies have demonstrated that the NCAM1–TTC12–ANKK1–DRD2 gene cluster plays essential roles in addictions in subjects of European and African origin,study of Chinese Han subjects is limited.Further,except DRD2,the underlying biological mechanisms of other genes are largely unknown.In smoking cohort,we found two missense variants(rs11604671;rs2734849)and an intronic variant(rs4648317)with significant effects on ND and further explored their mechanisms of action through expression and methylation analysis.We found the majority of smoking-related DMRs are located in the ANKK1/DRD2 region,indicating a likely causative relation between non-synonymous SNPs and DMRs.Our results offer strong clues to show that besides DRD2,ANKK1 plays essential role in smoking,as well.(3)Genetic and epigenetic analysis revealing the genetic mechanism in the serotonergic genes with smoking:Although pathological research reports that the serotonergic genes have great effects on addictive diseases,less SNPs were validated by independent cohorts.Only SNP-SNP interaction effects with smoking behavior has detected in European or African cohorts.In our study,we showed a haplotype block constructed by rs3758987 and rs4938056 in HTR3 B,which had significant association with ND.We further showed these SNPs contribute to ND through four methylated sites in HTR3 B.All these findings suggest that variants in the serotonergic system play an important role in ND in the Chinese Han population.More importantly,these findings demonstrated that the involvement of this system in ND is through gene-by-gene interaction and methylation.In summary,this study demonstrates the effects of functional variants on nicotine dependence by multi-omic analysis with men in Shanxi province of China.We used candidate genes association analysis,gene-gene interaction analysis,and cis-meQTL analysis to comprehensively extend our knowledge of the biologic mechanism of the candidate genes and variants.A good understanding of the SNPs will help us find pharmacologic targets to account for the addictive properties and look for an effective smoking cessation drug of nicotine in Chinese smokers.