EGR3 deletion attenuates developmental and epileptic encephalopathy in Kcna1-null mice.

Abstract

KCNA1 encodes the α-subunit of the voltage-gated potassium channel KV1.1. Mutations in KV1.1's pore domain result in developmental and epileptic encephalopathy (DEE), where early life seizures and a culprit lesion synergistically disrupt neurodevelopmental trajectories, resulting in intellectual disability that often presents with disturbances in sleep, sociability and sensory processing. Abnormalities in the subcellular localization of Kv1.1, via mutations in/autoantibodies against LGI1 and CNTNAP2, also give rise to syndromes of epilepsy and neuropsychiatric impairment. Mice with deletions of Kcna1("-/-") are known to display spontaneous seizures at 2-3 weeks of age and premature mortality. In this study, we applied instrumented home-cage monitoring to examine how aberrations in KCNA1 expression may result in pervasive alterations in spontaneous behavior. Compared to wildtype, Kcna1-/- mice displayed a robust multifaceted behavioral syndrome featuring marked nocturnal hyperactivity, reduced sleep and sheltering, fragmented feeding/drinking rhythms, abnormal sensory responsivity and diminished wheel-running. In similar recordings, Kcna1+/- mice only displayed increased sheltering, Lgi1+/- mice displayed mild sleep reductions and Cntnap2-/- mice showed home-cage hypoactivity. Kcna1 loss in parvalbumin-positive interneurons (PV-Cre) resulted in a subtle phenocopy, with mild reductions in sleep accompanied by reduced sheltering behavior, while Kcna1 deletions in forebrain pyramidal neurons (Emx1-Cre) or dopaminergic neurons (DAT-Cre) were asymptomatic. Adult-onset conditional deletions of Kcna1 also produced only mild sleep loss 6 weeks later. To survey the molecular landscape in Kcna1-/- mice, we conducted a mass spectrometry proteomic analysis of dissected hippocampal tissue (a predominant seizure onset zone and where astrogliosis is observed). This revealed significant upregulations in brain-derived neurotrophic factor (BDNF) and the immediate early transcription factor, early growth response-3 (EGR3), which is necessary for the induction of BDNF following electroconvulsive seizures. Heterozygous or homozygous deletions of Egr3 in Kcna1-/- mice resulted in significant survival prolongation, a partial suppression of neurobehavioral impairments, and a significant reduction in the frequency of spontaneous seizures and spreading depolarization events. These phenotypic corrections were associated with an amelioration of BDNF induction, hippocampal astrogliosis and proteomic disturbances. Together, these data demonstrate how disruptions to an ion channel that governs neuronal excitability at millisecond timescales can pleiotropically alter spontaneous behavior over much longer time scales. Our results provide a model and a set of precision endpoints to understand how ictal and interictal features of DEE may manifest through long-term transcriptional alterations imparted by early life seizures.