Critical contributions of neuronal subtypes to pediatric drug-resistant focal dysplasia.

Approximately 75% of epilepsy cases emerge in childhood, and 10%-30% of these pediatric epilepsy cases are resistant to standard drug therapies; however, the underlying causes of resistance remain poorly understood. Focal cortical dysplasia (FCD) is a primary contributor to pediatric epilepsy and is often associated with drug resistance. We performed single-nucleus RNA sequencing (snRNA-seq) and patch-clamp recording of fresh brain tissue samples that were obtained from pediatric FCD patients during surgery. Our study revealed significant transcriptomic changes across multiple subtypes of excitatory neurons and GABAergic neurons. Among the identified neuronal subtypes, the three inhibitory neuronal subtypes PVALB_RGS5, VIP_CRH, and SST_PENK presented prominent transcriptomic alterations related to epilepsy. The expression of genes enriched in epilepsy-related signaling pathways, especially those associated with excitatory/inhibitory (E/I) balance and energy metabolism, was significantly altered in these neuronal subtypes. Differentially expressed genes (DEGs) in the PVALB_RGS5 subtype were particularly enriched in pathways related to synaptic function. Recordings from fast-spiking (FS)/parvalbumin-containing neurons in brain sections from patients with FCD revealed a reduction in excitatory synaptic inputs, which indicates fewer synaptic inputs onto these neurons and lower activity. In addition, astrocyte subtype 4 exhibited distinct metabolic characteristics and interaction patterns with neuronal subtypes, which suggests their significant role in epilepsy pathophysiology. Our findings indicate that several specific neuronal and astrocyte subtypes play critical roles in the genesis and/or progression of drug-resistant pediatric seizures and that targeting these subtypes may represent a new treatment option.