Distinct Functional Alterations and Therapeutic Options of Two Pathological De Novo Variants of the T292 Residue of GABRA1 Identified in Children with Epileptic Encephalopathy and Neurodevelopmental Disorders

Abstract

Mutations of GABAAR have reportedly led to epileptic encephalopathy and neurodevelopmental disorders. We have identified a novel de novo T292S missense variant of GABRA1 from a pediatric patient with grievous global developmental delay but without obvious epileptic activity. This mutation coincidentally occurs at the same residue as that of a previously reported GABRA1 variant T292I identified from a pediatric patient with severe epilepsy. The distinct phenotypes of these two patients prompted us to compare the impacts of the two mutants on the receptor function and to search for suitable therapeutics. In this study, we used biochemical techniques and patch-clamp recordings in HEK293 cells overexpressing either wild-type or mutated rat recombinant GABAARs. We found that the α1T292S variant significantly increased GABA-evoked whole-cell currents, shifting the dose–response curve to the left without altering the maximal response. In contrast, the α1T292I variant significantly reduced GABA-evoked currents, shifting the dose–response curve to the right with a severely diminished maximum response. Single-channel recordings further revealed that the α1T292S variant increased, while the α1T292I variant decreased the GABAAR single-channel open time and open probability. Importantly, we found that the T292S mutation-induced increase in GABAAR function could be fully normalized by the negative GABAAR modulator thiocolchicoside, whereas the T292I mutation-induced impairment of GABAAR function was largely rescued with a combination of the GABAAR positive modulators diazepam and verapamil. Our study demonstrated that α1T292 is a critical residue for controlling GABAAR channel gating, and mutations at this residue may produce opposite impacts on the function of the receptors. Thus, the present work highlights the importance of functionally characterizing each individual GABAAR mutation for ensuring precision medicine.

Characterization of the zebrafishgabra1sa43718/sa43718germline loss of function allele confirms a function for Gabra1 in motility and nervous system development

“…This is consistent with functional analysis of the p.T292I patient variant we discovered. Chen and colleagues established that the pT292I variant can produce a receptor in HEK293 cells, but reduces channel open time 12 . Interestingly and despite a normal morphology, Samarut and colleagues showed 460 differentially expressed genes in gabra1 mutant brains.…”

“…GABRA1 encodes for the α1 subunit of the GABA A R and to date, over 30 different variants in the GABRA1 gene have been reported and associated with neurological disorders and neurodevelopmental defects [2][3][4][5][6][7][8][9][10][11] . Subsequent studies have demonstrated that the c.875C>T mutation is a loss of function allele that reduces single channel open time 12 .…”

Variable Expression of GABAA Receptor Subunit Gamma 2 Mutation in a Nuclear Family Displaying Developmental and Encephalopathic Phenotype

“…Alongside other GABR mutants that contribute to DEE such as GABRA1 [ 24 , 51 ], many other non-GABR ion channel or non-ion channel genes also contribute to DEEs. These genes are involved in kinase activity (cyclin-dependent kinase-like 5) [ 52 ], ion channel function (sodium voltage-gated channel alpha subunits 1, 2, and 8; potassium voltage-gated channel subfamily Q member 2) [ 53 , 54 , 55 , 56 ], cell adhesion (protocadherin 19) [ 57 ], and general cell homeostasis (tuberous sclerosis complex) [ 58 ].…”

Sex-specific transcriptional rewiring in the brain of Alzheimer’s disease patients

“…2022.1009368 Frontiers in Aging 10 frontiersin.org GABRA1 and GABRD, were linked to nicotine addiction in M-AD. A mutation in GABRA1 has been reported in epileptic encephalopathy in children (Chen W. et al, 2022). GABRA1 was identified as a therapeutic target of clinical AD drugs (Aggarwal et al, 2006;Xu Y. et al, 2021).…”