A Study Investigating the Role of 2 Candidate SNPs in Bax and Bcl-2 Genes in Alzheimer's Disease.

OBJECTIVE: The proto-oncogene Bax (Bcl-2-associated X protein) and related protein Bcl-2 (B-cell chronic lymphocytic leukemia/lymphoma-2) genes are triggers of apoptosis in Alzheimer's disease (AD). The balance of these proteins has an important role in the death or life of a neuronal cell, and the functional polymorphisms in genes expressing these proteins have been found to promote apoptosis. To investigate the role of Bax and Bcl-2 genes in AD, we examined the presence of the 2 polymorphisms in peripheral blood. To our knowledge, this is the first clinical association study of these 2 functional SNPs using the peripheral blood of patients with AD. METHODS: Bax (rs4645878) and Bcl-2 (rs2279115) in Alzheimer's patients (N = 132) and healthy controls (N = 109), aged 65 to 85 years, were analyzed by qPCR (Quantitative Polymerase Chain Reaction) using TaqMan probe technology. Statistical analyses were done using SPSS, 11.5. The differences between groups were analyzed using an independent-samples t test. The relationships between genotypes and alleles were analyzed using chi-square or likelihood ratio test. The Hardy-Weinberg balance was checked for the patient and control groups. A p-value of less than 0.05 was taken as significant. RESULTS: Sporadic AD patients and non-demented age matched control subjects were genotyped in this case-control study. No statistically significant relationship was found between the patients and controls for allele or genotype frequencies (p>0.05). CONCLUSION: Our data suggest that these two polymorphisms do not contribute to AD in the population from the Mersin region of the Eastern Mediterranean. Further studies with larger sample sizes must be conducted to ascertain the association between the 2 polymorphisms.

SNP Variation in MicroRNA Biogenesis Pathway Genes as a New Innovation Strategy for Alzheimer Disease Diagnostics: A Study of 10 Candidate Genes in an Understudied Population From the Eastern Mediterranean.

Alzheimer disease (AD) is a common complex neurodegenerative disorder accounting for nearly 50% to 70% of dementias worldwide. Yet the current diagnostic options for AD are limited. New diagnostic innovation strategies focusing on novel molecules and pathways are sorely needed. In this connection, microRNAs (miRNAs) are conserved small noncoding RNAs that regulate posttranscriptional gene expression and are vital for neuronal development and its functional sustainability. Conceivably, biological pathways responsible for the biogenesis of miRNAs represent a veritable set of upstream candidate genes that can be potentially associated with the AD pathophysiology. Notably, whereas functional single-nucleotide polymorphisms (SNPs) in miRNA biogenesis pathway genes have been studied in other complex diseases, surprisingly, virtually no such study has been conducted on their relevance in AD. Moreover, novel diagnostics identified in easily accessible peripheral tissues such as the whole blood samples represent the initial entry or gateway points on the biomarker discovery critical path for AD. To the best of our knowledge, we report here the first association study of functional SNPs, as measured by real-time PCR in 10 "upstream" candidate genes critically situated on the miRNA biogenesis pathway, in a large sample of AD patients (N=172) and healthy controls (N=109) in a hitherto understudied world population from the Mersin region of the Eastern Mediterranean. We observed a significant association between 2 candidate genes and AD, TARBP2 rs784567 genotype and AD (χ=6.292, P=0.043), and a trend for RNASEN rs10719 genotype (χ=4.528, P=0.104) and allele (P=0.035). Functional SNP variations in the other 8 candidate genes (DGCR8, XPO5, RAN, DICER1, AGO1, AGO2, GEMIN3, and GEMIN4) did not associate with AD in our sample. Given the putative biological importance of miRNA biogenesis pathways, these emerging data can provide a new foundation to stimulate future debate and genetic investigations of AD, focusing on new molecular mechanisms such as miRNA biogenesis, particularly in accessible peripheral tissues for novel molecular diagnostics for dementia.