Lack of association between rs597668 polymorphism near EXOC3L2 and late-onset Alzheimer's disease in Han Chinese

Untangling huge literature to disinter genetic underpinnings of Alzheimer's Disease: A systematic review and meta-analysis

Drug discovery for Alzheimer's Disease (AD) is channeled towards unravelling key disease specific drug targets/genes to predict promising therapeutic candidates. Though enormous literature on AD genetics is available, there exists dearth in data pertinent to drug targets and crucial pathological pathways intertwined in disease progression. Further, the research findings revealing genetic associations failed to demonstrate consistency across different studies. This scenario prompted us to initiate a systematic review and meta-analysis with an aim of unearthing significant genetic hallmarks of AD. Initially, a Boolean search strategy was developed to retrieve case-control studies from PubMed, Cochrane, ProQuest, Europe PMC, grey literature and HuGE navigator. Subsequently, certain inclusion and exclusion criteria were framed to shortlist the relevant studies. These studies were later critically appraised using New Castle Ottawa Scale and Q-Genie followed by data extraction. Later, meta-analysis was performed only for those Single Nucleotide Polymorphisms (SNPs) which were evaluated in at least two different ethnicities from two different reports. Among, 204,351 studies retrieved, 820 met our eligibility criteria and 117 were processed for systematic review after critical appraisal. Ultimately, meta-analysis was performed for 23 SNPs associated with 15 genes which revealed significant associations of rs3865444 (CD33), rs7561528 (BIN1) and rs1801133 (MTHFR) with AD risk.

Association of lectin-like oxidized low density lipoprotein receptor 1 (OLR1) polymorphisms with late-onset Alzheimer disease in Han Chinese

Background

Lectin-like oxidized low density lipoprotein receptor 1 (OLR1) locates within the area of chromosome 12p, which has been identified as the AD-susceptible region, and plays a role in lipid metabolism. Therefore, it has been suggested to be a good candidate gene for Alzheimer's disease (AD). Several SNPs within OLR1 have been reported to have association with AD among Caucasians.

Methods

We selected and genotyped three SNPs (rs1050283, rs1050286, rs17808009) in OLR1 to investigate its possible relationship with the onset of late-onset Alzheimer disease(LOAD) in 984 LOAD cases and 1,354 healthy controls among northern Han Chinese.

Results

No significant association was found between the OLR1 (rs1050283, rs1050286, rs17808009) polymorphisms and LOAD, even after adjustment for gender and age and stratification for apolipoprotein E (APOE) status.

Conclusions

Our study showed that the SNPs (rs1050283, rs1050286, rs17808009) located in the 3'UTR of OLR1 may not involve in the mechanism of LOAD in Han Chinese population.

INPP5D rs35349669 polymorphism with late-onset Alzheimer's disease: A replication study and meta-analysis

Inositol polyphosphate-5-phosphatase (INPP5D) was reported to be associated with Alzheimer's disease (AD) through modulating the inflammatory process and immune response. A recent genome-wide association study discovered a new locus single nucleotide polymorphism (SNP, rs35349669) of INPP5D which was significantly associated with susceptibility to late-onset Alzheimer's disease (LOAD) in Caucasians. In this study, we investigated the relations between the INPP5D polymorphism rs35349669 and LOAD in Han Chinese population comprising 984 LOAD cases and 1352 healthy controls being matched for age and gender. Our results showed no obvious differences in the genotypic or allelic distributions of rs35349669 polymorphism between LOAD cases and healthy controls (genotype: p = 0.167; allele: p = 0.094). Additionally, when these data were stratified by APOEε4 status, there are still no evident differences in the genotypic or allelic distributions in APOEε4 carriers (p > 0.05). Furthermore, meta-analysis of 81964 individuals confirmed that rs35349669 was significantly associated with the risk for LOAD (OR=1.08, 95%CI=1.06-1.11), but the results remained negative in Chinese subgroup (OR=0.77, 95%CI=0.53-1.13). Overall, the current evidence did not indicate that INPP5D rs35349669 polymorphism play a role in the genetic predisposition to LOAD in Chinese population.

ZCWPW1 is associated with late-onset Alzheimer's disease in Han Chinese: a replication study and meta-analyses

Recently, a large genome-wide association study (GWAS) has identified a novel variant (rs1476679) within ZCWPW1 showing strong association with late-onset Alzheimer's disease (LOAD) in Caucasian. However, the effect of rs1476679 on other populations remains unclear. In order to explore whether rs1476679 is also associated with the LOAD risk in other ethnic groups, we recruited 2350 unrelated Northern Han Chinese subjects, which include 992 LOAD patients and 1358 healthy controls. Analysis of data from these subjects suggests that the rs1476679 polymorphism is significantly associated with the LOAD (genotype P = 0.017, allele P = 0.044). The logistic regression reveals the C allele at rs1476679 is a protective factor for LOAD in the dominant model (OR = 0.779, 95%CI = 0.659–0.921, Pc = 0.009) adjusting for gender, age and APOE ε4 status. Furthermore, rs1476679 can decrease the AD risk (Dominant: OR = 0.733, 95%CI = 0.607–0.884, Pc = 0.006; Additive: OR = 0.820, 95%CI = 0.708–0.950, Pc = 0.048) in APOE ε4 non-carriers after stratification. Furthermore, meta-analysis of 82525 individuals confirmed that rs1476679 within ZCWPW1 decreased the risk of LOAD (OR = 0.91, 95%CI = 0.89–0.94). To summarize, the rs1476679 polymorphism in ZCWPW1 is associated with LOAD in Northern Han Chinese population.

NME8 rs2718058 polymorphism with Alzheimer's disease risk: a replication and meta-analysis

Recently, a large meta-analysis of five genome wide association studies (GWAS) has identified that a novel single nucleotide polymorphism (SNP) rs2718058, adjacent to gene NME8 on chromosome 7p14.1, was associated with late-onset Alzheimer's disease (LOAD) in Caucasians. However, the effect of rs2718058 on other populations remains unclear. In order to explore the relationship between rs2718058 and LOAD risk in a North Han Chinese population, we recruited 984 LOAD cases and 1354 healthy controls that matched for sex and age in this study. The results showed no significant differences in the genotypic or allelic distributions of rs2718058 polymorphism between LOAD cases and healthy controls, even though after stratification for APOE ε4 status and statistical adjustment for age, gender and APOE ε4 status (p > 0.05). However, a meta-analysis conducted in a sample of 82513 individuals confirmed a significant association between SNP rs2718058 and LOAD risk (OR = 1.08, 95%CI = 1.05-1.11) in the whole population. But there was still no positive results in Chinese subgroup (OR = 1.05, 95%CI = 0.93-1.17). In conclusion, the rs2718058 near gene NME8 on chromosome 7p14.1 might not play a major role in the genetic predisposition to LOAD in the North Han Chinese.

EXOC3L2 rs597668 variant contributes to Alzheimer's disease susceptibility in Asian population

Recent genome-wide association studies have established the association between EXOC3L2 rs597668 variant and Alzheimer's disease (AD) in European population. However, recent studies reported inconsistent results in Asian population. Here, we performed a systematic review and meta-analysis to evaluate the impact of rs597668 on AD risk in Asian population using a total of 8686 samples including 2855 cases and 5831 controls. Meanwhile, we selected 17,008 AD cases and 37,154 controls in European population to evaluate the potential heterogeneity between East Asian and European populations. In East Asian population, we identified no potential heterogeneity with P=0.31 and I² = 15.8%. By meta-analysis, we identified positive association between rs597668 and AD risk with P=0.023, OR=0.93, 95% CI 0.87-0.99. We further found significant heterogeneity in pooled Asian and European populations with P<0.0001 and I² = 87.7%. The meta-analysis indicated negative association with P=0.66, OR=0.97, 95% CI 0.85-1.11. In summary, all these findings indicate that rs597668 C allele is a risk factor for AD in European population with OR=1.18 and P=2.49E-13. However the rs597668 C allele played a protective role in AD with OR=0.93 and P=0.023 in East Asian population.

Association between EXOC3L2 rs597668 polymorphism and Alzheimer's disease

BACKGROUND

EXOC3L2 gene rs597668 polymorphism was identified to be significantly associated with Alzheimer's disease (AD) in Caucasian population. However, recent studies reported consistent and inconsistent results in Caucasian and Asian populations.

AIMS

In order to assess this association, we performed a meta-analysis of rs597668 polymorphism using RevMan (v.5.1) software.

METHODS

We searched PubMed and Google scholar databases and selected 4 independent publications, which included 16 independent studies. We conducted sensitivity analysis and evaluated the publication bias. In the end, we calculated the odds ratio (OR) using fixed effect model (Mantel-Haenszel).

RESULTS

We observed significant association between rs597668 polymorphism and AD using allele model (P = 0.006, OR = 1.09, 95% CI 1.03-1.16) and the dominant model (P = 0.008, OR = 1.11, 95% CI 1.03-1.21).

DISCUSSION AND CONCLUSIONS

To our knowledge, this is the first study that assesses the association between rs597668 polymorphism and AD by meta-analysis. We believe that our findings will be very useful for future genetic studies in AD.

SLC26A4 gene polymorphism and late-onset Alzheimer's disease in a Han Chinese population from Qingdao, China

In a recent genome-wide association study, the SLC26A4 gene rs2072064 polymorphism was found to be associated with late-onset Alzheimer's disease in Caucasians. Here, we investigated this association in a large Northern Han Chinese cohort consisting of 599 sporadic late-onset Alzheimer's disease patients and 598 healthy controls matched for sex and age in a Northern Han Chinese population from Qingdao, China. Genotyping by the polymerase chain reaction-ligase detection reaction revealed that there were significant differences in the genotype (P = 0.017) and allele (P = 0.007) frequencies of the rs2072064 polymorphism between late-onset Alzheimer's disease patients and controls. The A allele of this polymorphism was significantly associated with a reduced risk of late-onset Alzheimer's disease (odds ratio (OR) = 0.792, 95% confidence interval (CI) = 0.670-0.937, P = 0.007). When the data were stratified by the apolipoprotein E ε4 status, there was a significant difference only among apolipoprotein E ε4 non-carriers (genotypic P = 0.001, allelic P = 0.001). Furthermore, the association between rs2072064 and late-onset Alzheimer's disease remained significant by logistic regression analysis after adjustment for age, gender, and the apolipoprotein E ε4 carrier status (dominant model: OR = 0.787, 95% CI = 0.619-1.000, P = 0.050; recessive model: OR = 0.655, 95% CI = 0.448-0.959, P = 0.030; additive model: OR = 0.792, 95% CI = 0.661-0.950, P = 0.012). These findings suggest that SLC26A4 is a susceptibility gene for late-onset Alzheimer's disease in a Northern Han Chinese population from the Qingdao area.