Genetic interaction between GABRA1 and ERBB4 variants in the pathogenesis of genetic generalized epilepsy

Epilepsy is a complex neurological disease that can be caused by both genetic and environmental factors. Many studies have been conducted to investigate the genetic risk variants and molecular mechanisms of epilepsy. Disruption of excitation-inhibition balance (E/I balance) is one of the widely accepted disease mechanisms of epilepsy. The maintenance of E/I balance is an intricate process that is governed by multiple proteins. Using whole exome sequencing (WES), we identified a novel GABRA1 c.448G>A (p.E150K) variant and ERBB4 c.1972A>T (p.I658F, rs190654033) variant in a Malaysian Chinese family with genetic generalized epilepsy (GGE). The GGE may be triggered by dysregulation of E/I balance mechanism. Segregation of the variants in the family was verified by Sanger sequencing. All family members with GGE inherited both variants. However, family members who carried only one of the variants did not show any symptoms of GGE. Both the GABRA1 and ERBB4 variants were predicted damaging by MutationTaster and CADD, and protein structure analysis showed that the variants had resulted in the formation of additional hydrogen bonds in the mutant proteins. GABRA1 variant could reduce the efficiency of GABA_A receptors, and constitutively active ERBB4 receptors caused by the ERBB4 variant promote internalization of GABA_A receptors. The interaction between the two variants may cause a greater disruption in E/I balance, which is more likely to induce a seizure. Nevertheless, this disease model was derived from a single small family, further studies are still needed to confirm the verifiability of the purported disease model.