The role of Methyl-CpG binding domain 3 (Mbd3) in epileptogenesis

Methyl CpG binding domain 3 (Mbd3) protein belongs to the MBD family of proteins and is responsible for reading the DNA methylation pattern. Our previous study showed increased levels of NuRD complex proteins, including Mbd3 protein, in the brains of epileptic animals. The present study investigated whether the Mbd3 protein determines the seizure threshold. An increase in Mbd3 protein levels was demonstrated in the entorhinal cortex/amygdala in the rat’s brain 4 hours after pentylenetetrazole (PTZ)-induced seizures. Reduction of Mbd3 level using shRNA coding AAV vector injected to the amygdala prolonged the latency time to the onset of an acute seizure in the PTZ challenge test. This was accompanied by increased anxiety in the open field test. An overexpression of Mbd3 using AAV decreased anxiety, increased their excitability in the open field test, and accelerated epileptogenesis in the PTZ-kindling model. mRNA profiling with RNA-seq upon increased expression of MBD3 was performed in a model of magnesium deficiency-induced epileptiform discharges in vitro , revealing time- and state-specific gene expression changes. Our data indicate the pro-epileptic properties of the Mbd3 protein in vivo and in vitro .