Authors :
Presenting Author: Lu Zhang, MD,PhD – Huashan Hospital
Yuncan Chen, MD,PhD – Huashan Hospital
Shimin xu, MD,PhD – Huashan Hospital
Yiqiao Wang, MD,PhD – Huashan Hospital
Yan Ge, MD,PhD – Huashan Hospital
Xunyi Wu, MD,PhD – Huashan Hospital
Rationale: Sudden unexpected death in epilepsy (SUDEP) is a leading cause of premature mortality in individuals with epilepsy and is driven by complex, poorly understood mechanisms involving cardiac, autonomic, and respiratory dysfunction. While genetic variants in SCN5A—which encodes the cardiac sodium channel NaV1.5—are well known for their role in cardiac excitability, their contribution to brain function remains largely unexplored. In a previous Chinese cohort, we identified a rare de novo SCN5A R1193W variant associated with SUDEP. To investigate whether this variant affects neuronal function, we characterized the baseline and activity-dependent expression of NaV1.5 in the brain and heart. Furthermore, we generated a knock-in mouse model carrying the R1193W variant and applied electrophysiological recordings and multi-omics profiling to evaluate its impact on seizure susceptibility and underlying neurophysiological mechanisms.
Methods:
The spatial and cell-type–specific distribution of NaV1.5 in the mouse brain was mapped using fluorescent in situ hybridization (FISH). Kainic acid-induced status epilepticus (SE) was used to examine activity-dependent changes in NaV1.5 expression in the heart and selected brain regions. A CRISPR/Cas9- generated knock-in mouse model harboring the SCN5A variant was generated. Seizure susceptibility was assessed using the pentylenetetrazol (PTZ)-induced seizure model. Whole-cell patch-clamp recordings in hippocampal slices were used to evaluate synaptic activity and neuronal excitability. Transcriptomic and proteomic analyses were performed on brain tissue to identify molecular alterations associated with the variant.
Results:
NaV1.5 exhibited region-specific expression in the brain, primarily in GABAergic neurons of the amygdala and glutamatergic neurons of the piriform cortex, with limited expression in the hippocampus. Acute SE led to reduced NaV1.5 expression levels in the heart but not in the brain. Knock-in mice carrying the SUDEP-associated SCN5A variant showed increased seizure susceptibility, elevated frequency of spontaneous excitatory postsynaptic currents (sEPSCs), and a hyperpolarized action potential threshold in CA1 pyramidal neurons, despite unaltered sodium and potassium current amplitudes, suggesting the presence of network-level hyperexcitability. Multi-omics analysis revealed significant downregulation of GABAergic signaling components, supporting a mechanism involving impaired inhibition and circuit imbalance.
Conclusions:
This study reveals that SCN5A, traditionally considered a cardiac gene, also plays a critical role in neuronal excitability. The SUDEP-associated R1193W variant promotes hippocampal hyperexcitability, enhances synaptic transmission, and disrupts inhibitory signaling in the brain. These findings highlight a previously unrecognized contribution of SCN5A to epilepsy and SUDEP risk through central nervous system mechanisms.
Funding: -