Genetic Variants Affect Longevity Through Genes Associated With DNA Damage And Repair System

DNA damage and repair is an important way to maintain genomic stability.Genomic stability is closely related to aging and longevity.Studies have shown that the DNA repair ability is significantly enhanced in long-lived animals.DNA damage repair function is determined by DNA damage repair enzymes;genetic polymorphisms on these genes,especially functional polymorphisms,may be involved in the expression or activity of the enzyme and thus affect DNA damage and repair.However,it is unclear which DNA damage and repair genes are involved in the decision of human longevity traits.This paper proposes to compare the single-nucleotide polymorphism(SNP)of DNA damage repair genes in centenarians(100 years old and above)with middle-aged populations,and to screen out DNA damage and repair genes related to human longevity.The biological role in determining the longevity of these genes is determined in model animal.First,the 177 DNA damage and repair related genes were searched and identified using the GO database.The middle-aged population was used as a control to find SNPs(p<10e-04,the p value depends on the p-value deviation value in the QQ plot;statistical power is greater than 0.7)that were significantly altered in centenarians on these genes(including the genomic region and the adjacent 500 kb region).A total of 5 DNA damage and repair SNP associated with longevity,rs174535(FEN1;OR=1.211);p=5.943e-06),rs1535(FEN1;OR=1.21;p=6.589e-06),rs174576(FEN1;OR=1.209;p=7.549e-06),rs174577(FEN1;OR=1.213;p=4.84e-06)and rs174548(DDB1;OR=1.216;p=4.048e-06).According to the distribution of minor allele frequency of GWAS data and eQTL data,the four SNPs of FEN1 in the centenarians all decreased the expression of FEN1,whereas the SNP of DDB1 increased the expression of DDB1.As FEN1 was down-regulated in centenarians,FEN1 homologue,crn-1,was knocked-down in Caenorhabditis.elegans(N2).Recombinase was used to construct the L4440 knockdown plasmid,after feeding the bacteria with knockdown plasmid in L3-L4 stage,qPCR results showed that crn-1 was significantly knocked-down compared to negative control.Crn-1 was also significantly knocked-down in reproductive-suppressed sqt-3 worms.Crn-1 knocked-down lines showed significant extension in both median and maximum lifespan by approximately 16%as compared to wild-type,suggesting that crn-1 is involved in the regulation of lifespan and inhibiting its expression can significantly extend the life of C.elegans.However,upon the hydrogen peroxide treatment,a reagent used to induce DNA damage,crn-1 knocked-down lines were observed to be sensitive to hydrogen peroxide-mediated oxidative stress,suggesting that crn-1 knocked-down mediated lifespan extension in C.elegans is not caused by improved DNA repair ability.Finally,we found that knockdown of crn-1 expression can decrease the hatching rate,that suggests crn-1 may be involved in organismal development.Meanwhile,after feeding the bacteria with knockdown plasmid in L3-L4 stage,qPCR results showed that ddb-1 was significantly knocked-down compared to negative control.Ddb-1 was also significantly knocked-down in reproductive-suppressed sqt-3 worms.Ddb-1 knocked-down lines showed no significant extension in both median and maximum lifespan compared to wild-type,but,Ddb-1 knocked-down lines showed significant shortened in maximum lifespan by approximately 20%compared to wild-type in the case of UV induction,suggesting that ddb-1 is involved in DNA damage and repair process.In conclusion,our study found SNPs in genes responding to DNA damage and repair associated with longevity and their host genes FEN1 and DDB1 through centenarian GWAS study.Here we report for the first time,crn-1,homologue of human FEN1 in C.elegans,can extend both the median and maximum lifespan.We also found that the underlying mechanism of resulted lifespan extension is not due to the improvement for DNA damage resistance.