Genetic Variation In CLU Gene And Alzheimer’s Disease Risk In Han Chinese

Objective:To investigate whether polymorphisms of the Clusterin gene (CLU) have an effect on the risk for late onset Alzheimer’s disease (LOAD) in Han Chinese. Methods: 1、We performed sequencing of the CLU gene by using genomic DNA of 50 case and 50 control subjects matched for age and sex, who were selected randomly from the main study population. The CLU gene sequences within the promoter, exons the 5’and 3’ untranslated regions, and the exon-intron boundaries were involved. The CLU gene SNPs were further selected based on the criteria that minor allele frequency (MAF)≥0.05 and r2>0.82, and all the novel or known rare variants that were more prevalent in AD patients than in healthy controls.2、796 SAD patients and 796 healthy subjects matched for sex and age were recruited for the larger retrospective case-control study. The selected polymorphisms in CLU gene were genotyping and analyzed by polymerase chain reaction-ligase detection reaction (PCR-LDR) (TaqMan Assay). And the PCR-LDR was also used for the detection of APOE polymorphisms.3、The distribution frequency of alleles and genotypes of SNPs in LOAD group and control group was calculated with x2 analysis. Statistical analysis of the LOAD case and control subjects divided into the APOE □4-positive subgroup and APOE □4-negative subgroup was also carried out. To idenfiy the independent risk factor for AD, odds ratios (ORs) and 95% confidence intervals were tested using logistic regression models after adjustment for sex, age, and APOE □4 genotype. Results:1、A total of 18 variants in CLU gene were found in the sequencing analysis, including 11 previously reported variants in the SNP database as well as 7 new SNPs. According to the above criteria, a total of 11 variants were finally selected to be used to explore in the further research, including rs881146, rs7012010, rs17466684, rs17057441, rs2279591, rs9331949, rs9331942, rs3087554, rs3216167, rs7982, rs1532278.2、As expected, after classification, according to APOE gene, APOE □4 allele carriers have higer risk of LOAD than APOE □4 non-carrier patients (OR=1.854,95%CI=1.443-2.382, P<0.001).3、Among the eleven SNPs, we found that only the allele and genotype frequencies of rs9331949, which was located at the 3’ untranslated region (3’UTR) of CLU gene, were differed significantly between the AD group and control group (allelic association, P=0.003, genotypic, P=0.006). The minor allele C had an significant increased risk for LOAD when compared with the control group (OR=1.286,95%CI=1.088-1.519, P<0.001). What’s more, the rs9331949 C allele appeared to confer higher risk significantly in APOE □4 carriers (OR=1.625; 95%CI=1.087-2.430) than in non-APOE D4 carriers (OR=1.232; 95%CI=1.023-1.484) after classification according to carrying of APOE □4 alleles. Muti-factor logistic regression analysis also revealed that the rs9331888 polymorphism presented strong associations with LOAD (additibe model:p=0.004, OR=1.274,95%CI=1.082-1.499; dominant model:P=0.002, OR=1.975,95%CI=1.293-3.018). Haplotype analysis revealed two risk haplotypes (Hap 2:CG and Hap 4:TA) and one protective haplotype (Hap 3:TG). Conclusions:1. Our results suggested that APOE gene polymorphism correlates with LOAD in North Han Chinese, and the carriers of APOE □4 alleles have profound higer risk of LOAD.2. The polymorphisms of CLU were significantly correlated with the susceptibility of LOAD in Han Chinese, and the allele C of rs9331949, located at the 3’untranslated region, was significantly associated with an increased risk of LOAD.