The γ-aminobutyric acid type A receptors (GABA A Rs) are principal inhibitory receptors in the mature central nervous system (CNS). Genetic mutations in GABA A R subunits contribute to the pathogenesis of various neurological diseases by increasing (gain-of-function, GOF) or decreasing (loss-of-function, LOF) receptor function. Accurately distinguishing between GOF and LOF is crucial for selecting the appropriate medication and improving clinical outcomes. However, there is currently no consensus on how functional analyses should be performed or which criterion should be used to define GOF and LOF variants. In many recent publications, classification has been based mainly on the change in GABA EC50 for a given variant, which may not capture the full functional impact and sometimes misrepresents the true extent of functional changes, potentially leading to misleading conclusions under certain situations. Here, we functionally evaluated 23 previously uncharacterized GABRA1 missense variants and proposed a novel approach using the mutant (MT)/wild-type (WT) response ratio at the WT EC50 concentration, incorporating both EC50 and maximum response to classify GOF/LOF variants. This two-parameter approach resolved inaccuracies observed in single-parameter methods, particularly for variants with substantial changes in maximal response. We further applied this method to clinically analyze 58 GABRA1 missense variants identified in a cohort of 117 patients. Our analysis revealed that LOF variants are associated with higher seizure incidence and increased fever sensitivity, whereas GOF variants correlate with more severe cognitive impairment and movement disorders. Overall, this approach enhances the precision of functional analysis and clinical correlation of pathogenic GABA A R variants for better diagnosis of related disorders.
He et al. (Sun,) studied this question.