Institute of Fundamental Technological Research

Background: Depressive disorder, including recurrent type (rDD), is accompanied by increased oxidative stress and activation of inflammatory pathways, which may induce DNA damage. This thesis is supported by the presence of increased levels of DNA damage in depressed patients. Such DNA damage is repaired by the base excision repair (BER) pathway. BER efficiency may be influenced by polymorphisms in BER-related genes. Therefore, we genotyped nine single-nucleotide polymorphisms (SNPs) in six genes encoding BER proteins.

Material/Methods: Using TaqMan, we selected and genotyped the following SNPs: c.-441G>A (rs174538) of FEN1, c.2285T>C (rs1136410) of PARP1, c.580C>T (rs1799782) and c.1196A>G (rs25487) of XRCC1, c.*83A>C (rs4796030) and c.*50C>T (rs1052536) of LIG3, c.-7C>T (rs20579) of LIG1, and c.-468T>G (rs1760944) and c.444T>G (rs1130409) of APEX1 in 599 samples (288 rDD patients and 311 controls).

Results: We found a strong correlation between rDD and both SNPs of LIG3, their haplotypes, as well as a weaker association with the c.-468T>G of APEXI which diminished after Nyholt correction. Polymorphisms of LIG3 were also associated with early onset versus late onset depression, whereas the c.-468T>G polymorphism showed the opposite association.

Conclusions: The SNPs of genes involved in the repair of oxidative DNA damage may modulate rDD risk. Since this is an exploratory study, the results should to be treated with caution and further work needs to be done to elucidate the exact involvement of DNA damage and repair mechanisms in the development of this disease.

Depression, DNA Repair, Inflammation, Oxidative Stress, Polymorphism, Single Nucleotide

Background: An elevated levels oxidative modified DNA bases and a decreased efficiency of oxidative DNA damage repair were found in patients with depression disorders, including recurrent type (rDD). The glycosylases are involved in base excision repair (BER), which eliminates oxidative DNA damage. Therefore, we genotyped the single nucleotide polymorphisms (SNPs) of genes encoding three glycosylases: hOGG1, MUTYH and NEILL

Methods: We selected three polymorphisms: c.977C > G - hOGG1 (rs1052133), c.972G > C - MUTYH (rs3219489) and c.*589G > C - NEIL1 (rs4462560). A total of 555 DNA samples (257 cases and 298 controls) were genotyped using TaqMan probes.

Results: The C/C genotype and allele C of the c.*589G > C decreased the risk of rDD occurrence, while the G/G genotype and allele G of the same SNP increased the risk. This polymorphism had a stronger association with early-onset depression (patients with first episode <35 years of age) than with late onset depression (first episode >= 35 years of age). We did not find any significant differences in distribution of alleles and genotypes of other SNPs; however, the G/G genotype of the c.972G > C increased the risk of late onset rDD. We also found that combined genotype C/C-C/C of c.977C > G and c.*589G > C significantly reduced the risk of rDD.

Limitations: Limited sample size and ethnic homogeneity of the studied population.

Conclusion: This is the first study to show that SNPs of genes involved in DNA repair, particularly in BER pathway, may modulate the risk of rDD. These results further support the hypothesis on the involvement of DNA repair mechanisms in pathogenesis of depression.

Depression, Glycosylases, BER, DNA repair, DNA damage

Background: Many clinical studies have shown that oxidative stress pathways and the efficiency of the oxidative DNA damage base excision repair (BER) system are associated with the pathogenesis of Alzheimer's disease (AD). Reduced BER efficiency may result from polymorphisms of BER-related genes. In the present study, we examine whether single nucleotide polymorphisms (SNPs) of BER genes are associated with increased risk of AD. Methods: SNP genotyping was carried out on DNA isolated from peripheral blood mononuclear cells obtained from 120 patients with AD and 110 healthy volunteers. Samples were genotyped for the presence of BER-related SNPs, i.e.XRCC1-rs1799782, rs25487; MUTYH-rs3219489, and PARP1-rs1136410. Results: We found a positive association between AD risk and the presence of G/A genotype variant of the XRCC1 rs25487 polymorphism [odds ratio (OR) = 3.762,95% Cl: 1.793-7.8911. The presence of the A/A genotype of this polymorphism reduced the risk of AD (OR = 0.485,95% Cl: 0.271-0.870). In cases of the PARP1 gene rs1136410 polymorphism, we observed that the T/C variant increases (OR =4.159, 95% Cl: 1.978-8.745) while the T/T variant reduces risk (OR = 0.240,95% Cl: 0.114-0.556) of AD. Conclusions: We conclude that BER gene polymorphisms may play an important role in the etiology of AD. Diagnosing the presence or absence of particular genetic variants may be an important marker of AD. Further research on a larger population is needed. There is also a need to examine polymorphisms of other BER in the context of AD risk.

Alzheimer's disease, Base excision repair, Polymorphisms