Molecular and clinical description of patients with GABA A receptor gene variants ( GABRA1 , GABRB2 , GABRB3 , GABRG2 ): a cohort study, review of literature, and genotype‐phenotype correlations

Objective: GABAA receptor subunit variants have recently been associated with neurodevelopmental disorders and/or epilepsy. The phenotype linked with each gene is becoming better known. Because of their common molecular structure and physiological role, it seemed interesting to describe a putative phenotype associated with GABAA -receptor-related disorders as a whole and seek possible genotype/phenotype correlations.Methods: We collected clinical, electrophysiological, therapeutic, and molecular data from patients affected with GABAA receptor subunit variants (GABRA1, GABRB2, GABRB3, GABRG2) through a national French collaboration using the EPIGENE network and compared them to the one already described in the literature.Results: We gathered the reported patients in 3 epileptic phenotypes: 15 patients with fever-related epilepsy (40%), 11 with early developmental epileptic encephalopathy (30%), 10 with generalized epilepsy spectrum (27%), and 1 patient without seizures (3%). We did not find a specific phenotype for any gene, but we showed that the location of variants on the transmembrane (TM) segment was associated with a more severe phenotype, irrespective of the GABAA receptor subunit gene, whereas N-terminal variants seemed to be related to milder phenotypes.Significance: GABAA receptor subunit variants are associated with highly variable phenotypes despite their molecular and physiological proximity. None of the genes described here was associated with a specific phenotype. On the other hand, it appears that the location of the variant on the protein may be a marker of severity. Variant location may have important weight in the development of targeted therapeutics.