The association of the regulatory region of the presenilin-2 gene with Alzheimer's disease in the Northern Han Chinese population

Genetic Association between Presenilin 2 Polymorphisms and Alzheimer's Disease and Dementia of Lewy Body Type in a Japanese Population

Background/Aims

Mutations in the presenilin 2 (PSEN2) gene cause familial Alzheimer's disease (AD). Common polymorphisms affect gene activity and increase the risk of AD. Nonsynonymous polymorphisms in the PSEN2 gene showed Lewy body dementia (LBD) phenotypes clinically. Therefore, we aimed to investigate whether PSEN2 gene polymorphisms were associated with AD or LBD.

Methods

Seven single nucleotide polymorphisms (SNPs) of the gene were analyzed using a case-control study design comprising 288 AD patients, 76 LBD patients, and 105 age-matched controls.

Results

Linkage disequilibrium (LD) examination showed strong LD from rs1295645 to rs8383 on the gene in our cases from Japan. There were no associations between the SNPs studied here and AD onset, and haplotypic analyses did not detect genetic associations between AD and the PSEN2 gene. Although the number of the cases was small, the SNPs studied did not modify the risk of developing LBD in a Japanese population.

Conclusion

The common SNPs of the PSEN2 gene did not affect the risk of AD or LBD in a Japanese population. Because genetic variability of the PSEN2 gene is associated with behavioral and psychological symptoms of dementia (BPSD) in AD and LBD, further detailed analyses considering BPSD of both diseases would be required.

Mitochondrial diseases of the brain

Neurodegenerative disorders are debilitating diseases of the brain, characterized by behavioral, motor and cognitive impairments. Ample evidence underpins mitochondrial dysfunction as a central causal factor in the pathogenesis of neurodegenerative disorders including Parkinson's disease, Huntington's disease, Alzheimer's disease, Amyotrophic lateral sclerosis, Friedreich's ataxia and Charcot-Marie-Tooth disease. In this review, we discuss the role of mitochondrial dysfunction such as bioenergetics defects, mitochondrial DNA mutations, gene mutations, altered mitochondrial dynamics (mitochondrial fusion/fission, morphology, size, transport/trafficking, and movement), impaired transcription and the association of mutated proteins with mitochondria in these diseases. We highlight the therapeutic role of mitochondrial bioenergetic agents in toxin and in cellular and genetic animal models of neurodegenerative disorders. We also discuss clinical trials of bioenergetics agents in neurodegenerative disorders. Lastly, we shed light on PGC-1α, TORC-1, AMP kinase, Nrf2-ARE, and Sirtuins as novel therapeutic targets for neurodegenerative disorders.

Presenilin-2 polymorphisms and risk of sporadic AD: evidence from a meta-analysis

Association studies of presenilin-2 (PSEN2) polymorphisms and sporadic Alzheimer's disease (AD) have yielded inconsistent results, possibly because single studies often lack sufficient statistical power. In this study, we performed a meta-analysis to evaluate the association of the two most extensively studied PSEN2 polymorphisms, rs8383 and 5'indel, with the risk of sporadic AD. We systematically reviewed relevant studies retrieved by Medline, Pubmed, Embase, AlzGene, and CNKI. Data were analyzed using the Stata (v11.0) software package. The fixed effects model or random-effects model were applied depending on between-study heterogeneity. Publication bias was evaluated using Egger's test and Begg's funnel plots. Overall, the meta-analysis included 6 case-control studies for each polymorphism with 2186 confirmed AD cases and 2507 healthy controls in total. Analysis suggested a significant association between SNP rs8383 polymorphism and AD risk with no evidence of between-study heterogeneity or publication bias. In contrast, we found no evidence for an association between the 5'indel polymorphism and AD risk. Further stratified analyses by apolipoprotein ε4 status or ethnicity also failed to reveal a statistically significant association between the 5'indel polymorphism of PSEN2 and AD risk. Our analysis supports the hypothesis that the PSEN2 rs8383 polymorphism is associated with an enlarged risk of sporadic AD. However, larger scale association studies are necessary to further validate the association of PSEN2 polymorphisms with sporadic AD risk and to define potential gene-gene interactions.

The role of variation at AβPP, PSEN1, PSEN2, and MAPT in late onset Alzheimer's disease

Rare mutations in AβPP, PSEN1, and PSEN2 cause uncommon early onset forms of Alzheimer's disease (AD), and common variants in MAPT are associated with risk of other neurodegenerative disorders. We sought to establish whether common genetic variation in these genes confer risk to the common form of AD which occurs later in life (>65 years). We therefore tested single-nucleotide polymorphisms at these loci for association with late-onset AD (LOAD) in a large case-control sample consisting of 3,940 cases and 13,373 controls. Single-marker analysis did not identify any variants that reached genome-wide significance, a result which is supported by other recent genome-wide association studies. However, we did observe a significant association at the MAPT locus using a gene-wide approach (p = 0.009). We also observed suggestive association between AD and the marker rs9468, which defines the H1 haplotype, an extended haplotype that spans the MAPT gene and has previously been implicated in other neurodegenerative disorders including Parkinson's disease, progressive supranuclear palsy, and corticobasal degeneration. In summary common variants at AβPP, PSEN1, and PSEN2 and MAPT are unlikely to make strong contributions to susceptibility for LOAD. However, the gene-wide effect observed at MAPT indicates a possible contribution to disease risk which requires further study.

Pharmacogenetic Study on the Effect of Rivastigmine on PS2 and APOE Genes in Iranian Alzheimer Patients

Background/Aims

Alzheimer disease (AD) is a complex and genetically heterogeneous disorder, and certain genes such as PS2 and APOE4 contribute to the development of AD. Due to its heterogeneity, AD-predisposing genes could vary in different populations. Moreover, not all AD patients will respond to the same therapy. We specifically investigated the effect ofrivastigmine (Exelon) on PS2 and APOE genes in Iranian AD patients.

Methods

A total of 100 AD patients, 67 patients with sporadic AD (SAD) and 33 patients with familial AD (FAD), receiving rivastigmine therapy and 100 healthy controls were studied. PCR-RFLP was used for genotyping of PS2 and APOE.

Results

We found a positive association between the PS2 –A allele and SAD patients (p^c = 0.01), and the PS2 +A/–A genotype was significantly more frequent in SAD than FAD patients (p^c = 0.009). The APOE4 allele was associated with total AD, SAD and FAD (p^c = 0.000002). Patients with the PS2 +A/–A genotype and bigenic genotypes of +A/–A·∊3/∊3 and +A/–A·∊3/∊4 were the best responders to Exelon therapy, and those with the PS2 +A/+A and APOE ∊3/∊4 genotypes were the worst responders.

Conclusion

Our findings suggest that the PS2 and APOE4 alleles and genotypes affect both AD risk and response to rivastigmine therapy.

Association between NR2B subunit gene (GRIN2B) promoter polymorphisms and sporadic Alzheimer's disease in the North Chinese population

N-methyl-d-aspartate (NMDA) receptor plays a crucial role in learning, memory and information processing of human brain. Its dysfunction is related to the pathogenesis of Alzheimer's disease (AD). We detected four polymorphisms of the promoter regions of the human NMDA receptor 2B (NR2B) subunit gene (GRIN2B) in 362 AD patients and 334 healthy in North Han Chinese populations, these were -200T/G (rs1019385), -421C/A (rs3764028), -1447T/C (ENS10557853), and -1497G/A (rs12368476). Genetic analysis confirmed that there were significant differences in genotype (P=0.029) and allele (P=0.010) frequencies for -421C/A between SAD and control. In the subjects without APOE varepsilon4 allele, these difference remained significant (genotype P=0.012, allele P=0.004). The -421CC genotype was about 1.5 fold increasing risk compared with CA+AA genotypes (OR=1.517, 95% CI 1.077-2.137, P=0.017). Luciferase reporter assay showed a 34.69-39.79% decrease in transcriptional activity for -421C allele of GRIN2B promoter compared with -421A in SH-SY5Y and HeLa cell lines. Our study suggests that the -421C allele may induce lower GRIN2B transcriptional activity and NR2B protein expression, thus it is associated with AD.