Inhibition of DNA Methylation Impairs Synaptic Plasticity during an Early Time Window in Rats

Abstract

Although the importance of DNA methylation-dependent gene expression to neuronal plasticity is well established, the dynamics of methylation and demethylation during the induction and expression of synaptic plasticity have not been explored. Here, we combined electrophysiological, pharmacological, molecular, and immunohistochemical approaches to examine the contribution of DNA methylation and the phosphorylation of Methyl-CpG-binding protein 2 (MeCP2) to synaptic plasticity. We found that, at twenty minutes after theta burst stimulation (TBS), the DNA methylation inhibitor 5-aza-2-deoxycytidine (5AZA) impaired hippocampal long-term potentiation (LTP). Surprisingly, after two hours of TBS, when LTP had become a transcription-dependent process, 5AZA treatment had no effect. By comparing these results to those in naive slices, we found that, at two hours after TBS, an intergenic region of the RLN gene was hypomethylated and that the phosphorylation of residue S80 of MeCP2 was decreased, while the phosphorylation of residue S421 was increased. As expected, 5AZA affected only the methylation of the RLN gene and exerted no effect on MeCP2 phosphorylation patterns. In summary, our data suggest that tetanic stimulation induces critical changes in synaptic plasticity that affects both DNA methylation and the phosphorylation of MeCP2. These data also suggest that early alterations in DNA methylation are sufficient to impair the full expression of LTP.

Regulation of seizure-induced MeCP2 Ser421 phosphorylation in the developing brain

“…MeCP2 likely plays a pivotal role in regulating activity-dependent gene transcription important for neural function, maturation of spine density, neuronal connectivity, dendritic arborization, behavior (Cohen et al, 2011; Jiang et al, 2013; Kishi and Macklis, 2010; Luikenhuis et al, 2004; Mullaney et al, 2004; Shahbazian et al, 2002b; Zhou et al, 2006), and multple forms of synaptic plasticity, including synaptic scaling (Blackman et al, 2012; Qiu et al, 2012; Zhong et al, 2012) and Hebbian plasticity (Li et al, 2011; Moretti et al, 2006; Munoz et al, 2016; Weng et al, 2011). Mouse models of Rett Syndrome with decreased or blocked expression of MeCP2 show impaired LTP in area CA1 of the hippocampus (Asaka et al, 2006; Weng et al, 2011), changes in glutamate receptor expression including decreased NR2A (Asaka et al, 2006), behavioral deficits (Neul et al, 2010), and increased spontaneous seizure susceptibility (D’Cruz et al, 2010; Shahbazian et al, 2002a; Zhang et al, 2014).…”

“…Of the multiple phosphorylation sites that regulate MeCP2 function (Bellini et al, 2014), the neuronal-specific (Zhou et al, 2006) S421 site is highly regulated by activity, such as Schaffer collateral stimulation (Munoz et al, 2016), psychostimulant-induced plasticity (Deng et al, 2010, 2014), postsynaptic Ca 2+ influx, and CaMKII T286 phosphorylation (Zhou et al, 2006). In older animals, NMDARs are the primary mediator of synaptically driven MeCP2 S421 phosphorylation (Zhou et al, 2006); however, we hypothesized that elevated expression of CP-AMPARs and LT-VGCCs early in development may provide an additional route of Ca 2+ entry into neurons (Morton et al, 2013; Rakhade and Jensen, 2009; Sanchez et al, 2001).…”

Ryanodine Receptor-Mediated Calcium Release Has a Key Role in Hippocampal LTD Induction

“…Free-floating sections for immunofluorescence were prepared as previously described (Muñoz et al, 2016 ). Naïve slices or slices exposed to LTD induction protocols (plus or minus 20 μM ryanodine in both cases), were fixed for 30 min in 4% paraformaldehyde/4% sucrose and then placed in 30% sucrose (w/v).…”

Tuina Massage Improves Cognitive Functions of Hypoxic-Ischemic Neonatal Rats by Regulating Genome-Wide DNA Hydroxymethylation Levels

“…On the contrary, pathogenically, environment-sensitive epigenetic modifications have already been proven to be involved in neurogenesis [11], learning and memory [12], and synaptic plasticity [13]. Among various epigenetic modifications, DNA methylation on the fifth carbon of cytosine (5-methylcytosine, 5 mC) is the most extensively studied epigenetic modification which plays important roles in chromatin structure remolding, transcriptional suppression, and cellular differentiation [14–16].…”