In the mature central nervous system (CNS), oligodendrocytes provide support and insulation to axons thanks to the production of a myelin sheath. During their maturation to myelinating cells, oligodendroglial precursors (OPCs) follow a very precise differentiation program, which is finely orchestrated by transcription factors, epigenetic factors and microRNAs (miRNAs), a class of small non-coding RNAs involved in post-transcriptional regulation. Any alterations in this program can potentially contribute to dysregulated myelination, impaired remyelination and neurodegenerative conditions, as it happens in multiple sclerosis (MS). Here, we identify miR-125a-3p, a developmentally regulated miRNA, as a new actor of oligodendroglial maturation, that, in the mammalian CNS regulates the expression of myelin genes by simultaneously acting on several of its already validated targets. In cultured OPCs, over-expression of miR-125a-3p by mimic treatment impairs while its inhibition with an antago-miR stimulates oligodendroglial maturation. Moreover, we show that miR-125a-3p levels are abnormally high in the cerebrospinal fluid of MS patients bearing active demyelinating lesions, suggesting that its pathological upregulation may contribute to MS development, at least in part by blockade of OPC differentiation leading to impaired repair of demyelinated lesions.

Background and Purpose: Refractory status epilepticus is a clinical emergency associated with high mortality and morbidity. Increasing evidence suggests neuroinflammation contributes to the development of drug-refractoriness during status epilepticus. Here, we have determined the contribution of the ATP-gated P2X7 receptor, previously linked to inflammation and increased hyperexcitability, to drugrefractory status epilepticus and its therapeutic potential.Experimental Approach: Status epilepticus was induced via a unilateral microinjection of kainic acid into the amygdala in adult mice. Severity of status epilepticus was compared in animals with overexpressing or knock-out of the P2X7 receptor, after inflammatory priming by pre-injection of bacterial lipopolysaccharide (LPS) and in mice treated with P2X7 receptor-targeting and anti-inflammatory drugs.

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Background and Purpose Neonatal seizures represent a clinical emergency. However, current anti‐seizure medications fail to resolve seizures in ~50% of infants. The P2X7 receptor (P2X7R) is an important driver of inflammation, and evidence suggests that P2X7R contributes to seizures and epilepsy in adults. However, no genetic proof has yet been provided to determine what contribution P2X7R makes to neonatal seizures, its effects on inflammatory signalling during neonatal seizures, and the therapeutic potential of P2X7R‐based treatments on long‐lasting brain excitability. Experimental Approach Neonatal seizures were induced by global hypoxia in 7‐day‐old mouse pups (P7). The role of P2X7Rs during seizures was analysed in P2X7R‐overexpressing and knockout mice. Treatment of wild‐type mice after hypoxia with the P2X7R antagonist JNJ‐47965567 was used to determine the effects of the P2X7R on long‐lasting brain hyperexcitability. Cell type‐specific P2X7R expression was analysed in P2X7R‐EGFP reporter mice. RNA sequencing was used to monitor P2X7R‐dependent hippocampal downstream signalling. Key Results P2X7R deletion reduced seizure severity, whereas P2X7R overexpression exacerbated seizure severity and reduced responsiveness to anti‐seizure medication. P2X7R deficiency led to an anti‐inflammatory phenotype in microglia, and treatment of mice with a P2X7R antagonist reduced long‐lasting brain hyperexcitability. RNA sequencing identified several pathways altered in P2X7R knockout mice after neonatal hypoxia, including a down‐regulation of genes implicated in inflammation and glutamatergic signalling. Conclusion and Implications Treatments based on targeting the P2X7R may represent a novel therapeutic strategy for neonatal seizures with P2X7Rs contributing to the generation of neonatal seizures, driving inflammatory processes and long‐term hyperexcitability states.

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