Functional analysis of epilepsy-associated GABA_A receptor mutations using Caenorhabditis elegans

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Genetic generalized epilepsy (GGE) is significantly associated with GABA_A receptor subunit mutations.
• Over 150 GGE-associated variants exist, with many lacking validated pathogenicity.
• Developing robust in vivo models is crucial for assessing the functional impact of these variants.

Purpose of the Study:

• To establish Caenorhabditis elegans as a functional in vivo model for investigating GABA_A receptor subunit variants.
• To validate the pathogenicity of epilepsy-associated GABA_A receptor variants.
• To create a platform for the high-throughput screening of epilepsy-associated gene variants.

Main Methods:

• CRISPR-Cas9 gene editing was employed to generate unc-49 deletion and epilepsy-associated mutant strains in C. elegans.
• Phenotypic analysis of locomotion, shrinker frequency, and pentylenetetrazole (PTZ)-induced convulsions was performed.
• Rescue experiments utilized transgenes expressing C. elegans unc-49B or human GABA_A receptor subunits (α1, β3, γ2).

Main Results:

• The unc-49 deletion strain exhibited impaired locomotion, increased shrinker frequency, and heightened seizure-like activity.
• Phenotypic rescue was observed upon expression of C. elegans unc-49B or human GABA_A receptor subunits.
• Two epilepsy-associated variants were functionally characterized as loss-of-function, confirming their pathogenicity.

Conclusions:

• C. elegans provides a validated genetic model for studying GABA_A receptor mutations in epilepsy.
• This platform enables the functional validation of numerous epilepsy-associated variants.
• The study establishes a powerful tool for advancing epilepsy research and genetic diagnostics.