Altered oligodendroglial cell development and increased myelination in SCN2A gain-of-function-linked epilepsy.

Gain-of-function variants in SCN2A, encoding the voltage-gated sodium channel NaV1.2, cause developmental and epileptic encephalopathies characterized by seizures, developmental delay, and white matter abnormalities. While NaV1.2 is known to regulate neuronal excitability, its role in oligodendroglial cells is unclear. Here, we show that NaV1.2 is expressed in early oligodendrocyte lineage stages. In mice carrying the gain-of-function Scn2ap.A263V variant, oligodendrocyte precursor cells displayed similar NaV1.2 expression, but altered electrophysiological properties and calcium signaling. Single-cell transcriptomics revealed stage-specific changes in oligodendroglial maturation during early postnatal development, associated with lower variability and slightly faster conduction velocities. In adult mutant mice, gray matter myelination was increased without changes in oligodendrocyte numbers or myelin structure. Since NaV1.2 was absent from mature oligodendrocytes, the enhanced myelination likely reflects an activity-dependent adaptation to altered neuronal network activity rather than a primary myelinopathy. These findings identify a glial contribution to SCN2A-related disease mechanisms and underscore the need to consider neuron-glia interactions when developing targeted therapies for epilepsy.