No abstract

Aim: It is difficult to diagnose dementia with Lewy bodies (DLB) because it exhibits clinical and neuropathological overlap with both Alzheimer's disease and Parkinson's disease. The α-synuclein protein is a major component of Lewy bodies, and accumulation of α-synuclein aggregates causes synaptic dysfunction in DLB. Epigenetic changes at the synuclein alpha (SNCA) gene may be involved in DLB pathogenesis. Methods:We examined DNA methylation rates at 10 CpG sites located in intron 1 of SNCA and SNCA mRNA expression in peripheral leukocytes to compare DLB patients (n = 20; nine men, 11 women; age = 78.8 AE 7.7 years) with healthy controls (n = 20; eight men, 12 women; age = 77.0 AE 6.9 years). Results:The methylation rate at CpG 4 (P = 0.002) and the overall mean methylation rate at these sites (P < 0.001) were significantly lower in DLB patients than in healthy controls after Bonferroni correction. Although SNCA126, a partial form of SNCA mRNA expression, was significantly increased in DLB (P = 0.017), there was no significant difference in total SNCA mRNA expression between DLB patients and healthy controls (P = 0.165). No correlation was observed between SCNA mRNA expression levels and blood DNA methylation rates in either DLB or healthy controls. Conclusion:Our findings indicated that lower methylation rates may be a biomarker for DLB.

Despite the continuing debate about the amyloid hypothesis in Alzheimer's disease (AD), the precise pathogenesis is still unclear. Mixed pathology is common and multiple different protein aggregates are seen in human postmortem brains. Aggregates consisting of the alpha-synuclein protein encoded by the Synuclein Alpha gene (SCNA) are common in both dementia with Lewy bodies and AD. We examined SNCA mRNA expression and methylation rates of the CpG island at intron 1 of SNCA in peripheral leukocytes in 50 AD and age- and sex-matched control subjects to verify whether alpha-synuclein pathology affects the AD pathogenesis. SNCA mRNA expression in AD subjects was significantly higher than that in control subjects (1.62±0.73 versus 0.98±0.50, p < 0.001). We found significant differences between AD and control subjects at seven CpG sites (average rate; 8.8±2.7 versus 9.5±2.5, respectively: p = 0.027). The methylation rates tended to be lower in AD subjects at all CpG sites. We conclude that mRNA expression and methylation of SNCA intron 1 are altered in AD, which may be caused by Lewy body pathology in AD.

The ABCA7 mRNA expression level in peripheral blood may be a marker for early stages of AD and disease progression regardless of rs3764650 and the methylation rate of its promoter.

MEF2C mRNA expression in leukocytes may be a biological marker for cognitive decline in AD.