miR-211 is a neuronal regulator of cholinergic-induced seizures

Epilepsy, one of the most common brain disorders, poses aworld-wide health and social problem. Recent reports indicate thatboth cholinergic and microRNA (miRNA) mis-regulation areinvolved in generating the neuronal hyper-excitability and hyper-synchronization hallmarks of convulsive and non-convulsiveepileptic seizures; however, how the healthy brain avoids suchseizures remains unclear. Here, we report that miRNA-211suppresses non-convulsive seizures via the cholinergic and theTGFbR-II pathways. Our working hypothesis predicted thatneuronal miRNAs that regulate synaptic vesicle functioning couldcontrol neuronal hyper-excitability and seizure-related synchronizedfiring. By intersecting publicly available miRNA datasets we foundmiRNA-211 to be a putative regulator of synaptic vesicle processes,regulated by cholinergic-activation. Notably, neuronal miRNA-211is located in the 15q13.3 chromosomal locus (OMIM #612001), inwhich heterozygote microdeletions result in widely differing degreesof mental retardation and recurrent epileptic seizures, and homozy-gous deletions entail epileptic encephalopathy. Engineered double-transgenic mice (dTg-211), over-expressing doxycycline-suppressi-ble forebrain miRNA-211, showed impaired spatial learning and memory, but otherwise normal behavior. RNA-sequencing demon-strated that doxycycline-induced suppression of miR-211 excessinduced a wide transcriptional change in the frontal cortex,particularly in genes involved in synaptic activity, Ca+2transmem-brane transport, TGFbR-II signaling and higher brain functions.Concordantly, electrocorticography (ECoG) documented sponta-neous, non-convulsive seizures following miR-211 suppression.These events were accompanied by downregulation of the cholin-ergic muscarinic receptors. mAChR4 and mAChR2, known tonegatively affect cholinergic synaptic transmission, and elevation inmAChR5, and the nicotinic nAChR5 and nAChR7, which have areciprocal excitatory influence on synaptic transmission. Alongsidethe emergence of spontaneous seizures we noted a stepwiseelevation of the convulsive-seizure related miR-134, which doesnot change following mild epileptic preconditioning, and theinhibition of which prevents prolonged seizure-suppressive effects.Taken together, our findings indicate that miR-211 downregulationmay have a strong excitatory influence on CNS cholinergictransmission, and support cholinergic-mediated miRNA-211 controlover neuronal hyper-excitability and synchronized firing, whichlimits the consecutive emergence of non-convulsive and convulsive seizures.