Schedule of Events | Symposia

Functional Characterizations of CACNA1G variants Associated with Genetic Generalized Epilepsy

Poster Session F - Tuesday, April 1, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Athar sharifi^1,2 (athr.sharifi@gmail.com), Hang Lyu¹, Epi25 collaborative, Holger Lerche¹, Yuanyuan Liu¹; ¹Dept. of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tubingen, Germany, ²Dept. of Molecular Medicine, University of Padua, Padua, Italy

Background:There is a large body of evidence highlighting the fundamental role of voltage-gated calcium channels (CaVs) in neuronal function. Variants causing dysfunction of CaVs have been implicated in a variety of neurodevelopmental, neurological, and psychiatric disorders. CaV3.1 encoded by the CACNA1G gene, is a subtype of low-voltage activated T-type calcium channel. Variants in CACNA1G have been associated with epilepsy and ataxia. This study aims to elucidate the functional consequences of two CACNA1G variants, R198C and N1745S, which were identified in patients with genetic generalized epilepsy (GGE). Methods:The C592>T or A5111>G mutation was engineered into the human CaV3.1 channel cDNA by site-directed mutagenesis to generate the R198C or N1745S variant construct, respectively. Whole-cell patch clamp experiments were performed in transfected HEK293 cells to characterize the biophysical properties of the R198C and N1745S mutant and wild-type (WT) CaV3.1 channel. Results:The results showed that R198C significantly reduced the peak current density, while N1745S showed a trend towards lower peak current density compared to WT. Although both R198C and N1745S variants did not affect either the V1/2 or the time course of voltage-dependent activation and inactivation, they accelerated the deactivation time course at -50mV, -60mV and -70mV. Additionally, R198C increased the slope of the activation curve and slowed the recovery from inactivation. Conclusion:Our findings suggested that both R198C and N1745S variants caused a loss-of-function (LOF) effect, while R198C showed a stronger LOF than N1745S. These findings help to understand the pathophysiological mechanism underlying CACNA1G-related epilepsy(GGE). Keywords: CACNA1G, genetic generalized epilepsy, site-directed mutagenesis, calcium channel

Topic Area: METHODS: Electrophysiology