Identifying types of epilepsy-associated GABAA receptor variants for precision medicine

Abstract

Epilepsy is a highly heterogeneous neurological disorder, with a significant proportion of cases linked to genetic variants acecting ion channels that regulate neuronal excitability. Among these, pathogenic variants in subunits of the γ-aminobutyric acid type A (GABAA) receptor, a pentameric chloride channel responsible for fast inhibitory neurotransmission, are increasingly recognised as major contributors to genetic epilepsies, particularly developmental and epileptic encephalopathies (DEEs). Unfortunately, translating genetic findings into ecective, individualised treatment remains limited by our ability to functionally characterise variants of uncertain significance (VUS) and distinguish between gain-of-function (GoF) and loss-of-function (LoF) ecects. This thesis focuses on the identification and functional interpretation of epilepsy-associated GABAA receptor variants, with a particular emphasis on the GABRA6. A key aim was to enhance diagnostic precision by developing improved experimental pipelines for assessing the cell surface expression and gating properties of receptor variants. Using a combination of in silico prediction, structural mapping, and electrophysiological techniques, the work identifies patterns in variant localisation that correspond to distinct functional ecects. To support high-throughput and clinically relevant variant interpretation, this thesis also addresses key limitations in current surface expression assays. A revised cell surface quantification method was attempted for use in heterologous expression systems, to allow more accurate detection of tracicking-deficient GABRG2 variants that would otherwise evade diagnosis using standard electrophysiology alone. Integrating this assay into a diagnostic workflow strengthens our capacity to identify LoF variants, which are often associated with milder phenotypes, and to distinguish them from dominant-negative or GoF variants with more severe consequences. Collectively, the findings advance a structural and functional framework for interpreting GABAA receptor variants and demonstrate the importance of accurate cell surface expression analysis in the clinical classification of epilepsy-linked mutations. This approach contributes to the broader goal of precision medicine: delivering mechanistically informed, individualised treatments for patients with genetic epilepsies.

Date of Thesis submission	2025
Original language	English
Awarding Institution	Western Sydney University
Sponsors	Australian Government Research Training Program Scholarship
Supervisor	Nathan Absalom (Supervisor) & Chloe Goldsmith (Supervisor)