Posters

Epilepsy is a neurological disorder affecting approximately 70 million people worldwide, characterised by repeated seizures. This study used clinical EEG to explore the evolution of epileptogenic activity in a patient suffering from temporal lobe epilepsy with focal impaired awareness seizures. Recordings were classified into four distinct periods including control, two prodromal phases and symptomatic seizure. Morse wavelet time-frequency analysis of the four stages revealed an initial prodromal period characterised by a continuous alpha discharge followed by gradual increase in theta and delta activity during the second prodromal phase. The onset of symptoms was marked by a significant increase in delta and theta activity, accompanied by silencing of alpha waves. Functional connectivity using mutual information (MI) revealed a diffuse network connecting the left and right temporal lobes with a marked bilateral occipital component in the first prodromal phase. During the second prodromal phase, an epileptogenic focus was revealed in the right temporal lobe in the delta and theta bands, with a second network connecting the contralateral temporal lobe with occipital lobes in the beta/gamma bands. Source localisation identified the right V1-V5 as the main driver of alpha activity observed in the wavelet analysis. Source localisation during the seizure confirmed the focus in the ipsilateral temporal and frontal lobes with a remarkable mirrored appearance in the contralateral temporal and parietal association areas. This analysis revealed the presence of an extended epileptogenic network beyond the clinical focus and highlighted the utility of time-frequency analysis and MI in the characterisation of epileptogenic networks.

Developmental and epileptic encephalopathies (DEEs) are severe neurodevelopmental disorders defined by early-onset seizures and significant developmental delay. Many DEEs result from pathogenic variants in ion channel genes, highlighting the importance of understanding how altered channel function contributes to epilepsy and disrupted brain development. KCNH5 encodes the voltage-gated potassium channel Kv10.2 and has recently emerged as an epilepsy-associated gene, with multiple variants reported in public databases and clinical studies. Despite this, functional evidence is still lacking for most KCNH5 variants, and the mechanisms linking Kv10.2 dysfunction to epilepsy remain unclear. In this study, we report the effects of disease-associated KCNH5 mutations using electrophysiology in Xenopus oocytes. Most variants display gain-of-function in properties like gating behaviour and activation kinetics. Additionally, we present a novel knock-in mouse model carrying a mutation in the pore region of Kv10.2, corresponding to the most severe clinical phenotype in humans. Early observations suggest reduced viability in mutant animals, with limited survival after postnatal day 14 (P14), even in heterozygous condition. Our data , indicates that Kv10.2 is required during a critical period of early development and excessive channel activity is pathological. Overall, this work provides functional evidence for linking KCNH5 variant driven channel dysfunction to developmental changes and epilepsy mechanisms, and will guide future studies of additional KCNH5 variants and their impact in neurodevelopment.

Background: Status epilepticus (SE) is a neurological emergency associated with high morbidity and mortality, yet the early molecular changes accompanying sustained seizure activity remain incompletely understood. Heterogeneity between gene expression studies of animal SE models warrants a robust comparison to define the transcriptomic profile of SE across platforms, species, and experimental models.

Methods: We performed a meta-analysis of published gene expression studies of animal SE models encompassing the first 72 hours following SE onset. Twelve studies, comprising 37 transcriptomic datasets, were included, spanning species (mouse, rat) and experimental model (kainic acid, pilocarpine, self-sustaining SE). Pre-defined time windows (0-12, 12-24, 24-72 hours) were used to improve temporal resolution. Datasets were harmonised, mapped to human orthologues and analysed using multilevel linear mixed-effects models.

Results: Across all datasets, 444,693 animal gene entries mapped to human orthologs, yielding 17,215 unique human genes. Global analysis across time windows and SE models identified 118 differentially expressed genes (112 upregulated and 6 downregulated). Temporal analysis demonstrated largely distinct transcriptional profiles across time windows, with 83-87% of DEGs specific to their respective window. Four genes (FOS, TUBB6, TIMP1, HSPB1) were persistently upregulated across the first 24 hours following onset. Model-stratified analysis revealed distinct transcriptomic profiles across SE models. Pathway enrichment analysis identified early enrichment of inflammatory signalling pathways, including interleukin-17 (IL-17) signalling.

Conclusions: We provide a comprehensive molecular overview of early SE and show it be characterised by a highly dynamic, time-dependent transcriptomic response, with a small core of conserved dysregulated genes and prominent activation of pro-inflammatory cascades.

Background: KCNA6 encodes the voltage-gated potassium channel Kv1.6, a subunit involved in regulating neuronal excitability and action potential repolarization. Previous clinical case reports have demonstrated that KCNA6 mutations affecting potassium channel function correlate with a range of early infantile epileptic and neurodevelopmental disorder phenotypes. This report aims to document the condition of a novel mutation Kv1.6 p.Leu448Val in another patient exhibiting similar clinical features. Patient’s asymptomatic father did not carry the variant while mother’s DNA was not available.

Methods: Target mutant mRNA was obtained through site-directed mutagenesis, introduced into Xenopus laevis oocytes for expression, and its electrophysiological functional characteristics were assessed using the two-electrode voltage clamp technique. Wild-type and mutant RNA were also co-injected in 1:1 ratio. Results： This patient presented with febrile seizures before the age of one, accompanied by phenotypic features including global developmental delay, absent speech, and autism. The p.Leu448Val mutation is located within the S6 α-helical region, overlapping with previously reported mutations at the channel gate. Functional characterisation conducted in Xenopus oocytes revealed that the mutation disrupts the normal closure mechanism, resulting in increased potassium currents. These gain-of-function effects persisted when p.Leu448Val was co-injected with wild-type subunits.

Discussion: The clinical presentation of this individual and the electrophysiological features of the p.Leu448Val channel were consistent with the previously reported cases of KCNA6-associated epilepsy, confirming the pathogenicity of this variant. This case expands the clinical and genetic spectrum, and further establishes the causative role, of KCNA6 gain -of -function variants in developmental and epileptic encephalopathies .