Roles Of DNA Methylation In The Pathogenesis Of Parkinson's Disease

BackgroundThe etiology of PD remains unclear, genetic factors, environmental factors and their interactions are believed to contribute to the causes of the disease. The current flurry of research on DNA methylation and the increasing documentation of the effects of various environmental factors have expanded the scope of research on the etiology of various diseases including neurodegenerative diseases. However, DNA methylation is tissue-specific and in a dynamic-changing status. The obtanance of brain tissue is quite difficult and thus it is hard to led upport to follow-up research on methylation biomarkers. Some of the DNA metylation changes in brain tissue were consistent with that in peripheral blood. Studies using peripheral blood focused on DNA methylation of psychotic disorders and neurodegenerative diseases have achieved significant progress. Human peripheral blood mononuclear cells(PBMCs) represents a simple and readily accessible peripheral model to study DA-related mechanisms relevant for neurodegenerative diseases. Studies focousing on DNA methylation pattern of peripheral samples from sporadic PD patients is absent to date.ObjectiveIn the present study, we chose PBMCs from sporadic PD patients and healthy subjects as dopaminergic non-neural cell models to study the PD related changes of DNA methylation(including global methylation, expression of DNMTs and MBPs). MethodsGlobal methylation levels of genomic DNA were detected by ELISA Kit in62sporadic PD patients and63controls. Expression levels of DNMTs and MBPs were measured by real-time PCR in the same cohort. Statistic methods were used to analysis the difference between these two groups.Results1. Global DNA methylation is significantly lower in SPD than that in controls in PBMCs (P<0.05). The global DNA methylation levels of male SPD are significantly lower compared to female SPD(P<0.05).2. Age, onset-age, course of disease and L-dopa intake have no significant effect on global DNA methylation in PBMCs in SPD group and controls(P>0.05).3. Expression levels of DNMTs and MBPs are significantly elevated in PBMCs from SPD than that from controls (P<0.05).4. Expression levels of DNMT3A are inversely correlated with age in SPD(rs=-0.294, P<0.05) while expression levels of MBD4are positively correlated with age in SPD(rs=-0.294, P<0.05). Expression levels of DNMT3A are significantly elevated in male SPD compared to female SPD(P<0.05). Expression levels of MBD3are significantly lower in L-dopa-treated SPD compared the non-L-dopa-treated SPD(P<0.05).5. Global DNA methylation levels are inversely correlated with expression levels of DNMT1and MBD1in SPD PBMCs (rs[DNMT1]=-0.497, P<0.05, rs[MBD1]=-0.265, P<0.05), but not in control PBMCs(P>0.05). ConclusionsThis is the first research to detect the global DNA methylation levels and the expression levels of DNMTs and MBPs in PBMCs from SPD and control. Global DNA methylation levels and the expression levels of DNMTs and MBPs in PBMCs are significantly different between SPD and controls. Age, gender and L-dopa have effect on expression levels of DNMTs and MBPs in SPD patients. BackgroundDNA methylation changes were evident in PBMCs from sporadic PD patients. However, DNA methylation modifications were tissue specific. Brain tissue from animal models induced by enviromental toxics were considerable substitute while brain tissue from PD patients was not available yet. MPTP is the first and most classic enviromental factors found able to selectively induce dopaminergic neurons degeneration. The N-methyl group is necessary for the toxicity of MPTP/MPP+. The involvement of aberrant N-methylation processes of protein and lipid have been suggested in PD patients and animal models, so the PD-like symptoms may be related to the methylation process.Expression profiling in PD patients and animal models identified serious changes of gene expression. The role of DNA methylation, as one of the most important mechanisms for gene regulation, in MPTP induced PD models have not been studied. So we expanded our investigation of DNA methylation to brain tissue from substantia nigra region of MPTP-treated PD mice.ObjectiveTo identify the existantcy of abnarmal DNA methylation in the substantia nigra region of the MPTP-induced rodent PD model. To give a detailed profile of genome-wide methylation and to locate PD-related DNA methylation changes in substantia nigra region of the MPTP-induced PD mice model.Methods1. Eight-week old male C57/BL mice were treated with MPTP or saline intraperitonially. The behavior changes were observed and mesured by bar test.The extents of tyrosine hydroxylase loss were mesured by immunohistochemistry and Western Blot.2. The global DNA methylation levels of substantia nigra region were measured by ELISA Kit.3. Expression levels of DNMTs and MBPs in substantia nigra region were identified by real-time PCR.4. MeDIP-Chip method was used to performe gonome-wide analysis of DNA methylation change in substantia nigra region of MPTP-induced PD mice model.5. DNA methylation in the promotor region of Uchll in substantia nigra region were mesured by bisulfite sequencing PCR. Expression levels of Uch11in substantia nigra were mesured by Real-time PCR.Results1. PD-like behaviors were induced by successively intraperitonial administration of MPTP. Immunohistochemistry and Western Blot showed selectively loss of TH protein expression in substantia nigra region(P<0.05).2. The global DNA methyaltion level of tissue from substantia nigra region of MPTP-treat mice were significantly lower than that in the saline controls(P<0.05).3. Dnmt1, Dnmt3a and MBPs mRNA expression were detected in the substantia nigra region. The mRNA expression level of Dnmtl, Dnmt3a and MBPs in substantia nigra region of MPTP-treat mice were significantly increased than that in the saline controls(P<0.05).4. Gonome-wide DNA methylation chip analysis presented723methylated stes in the substantia nigra region from saline control and640methylated stes in the substantia nigra region from MPTP-treated models. We detected48sites, involving44genes, with significantly altered DNA methylation, the methylation levels of5genes were elevated and39were decreased. The abnormal-methylated genes involved in the biological processes concerning signal transduction, molecular transport, transcrption modulation, development, cell differentiation, regulation of apoptosis, oxidation reduction and protein catabolism.5. The DNA methylation levels of promotor region of Uchll in substantia nigra region of MPTP-treated mice were significantly higher than that in the saline controls(P<0.05).ConclusionsDNA methylation patterns are alterd in the substantia nigra region of MPTP-treated mice models. Global DNA methylation levels were decreased while expression levels of Dnmtl, Mbd1and Mecp2were elevated in the substantia nigra region of MPTP-treated mice models. We further confirmed that MeDIP-Chip is an effective method for genome-wide analysis of DNA methylation change. The detected PD-related gene with abnormal DNA methylation in substantia nigra region of MPTP-treated mice can be considered as target gene for further investigation.