Abstract
The leucine-rich repeat-containing family 8 member A (LRRC8A) is an essential subunit of the volume-regulated anion channel (VRAC). VRAC is critical for cell volume control, but its broader physiological functions remain under investigation. Recent studies in the field indicate that Lrrc8a disruption in brain astrocytes reduces neuronal excitability, impairs synaptic plasticity and memory, and protects against cerebral ischemia. In the present work, we generated the brain-wide conditional LRRC8A knock-out mice (LRRC8A bKO) using NestinCre-driven Lrrc8aflox/flox excision in neurons, astrocytes, and oligodendroglia. LRRC8A bKO animals were born close to the expected Mendelian ratio and developed without overt histological abnormalities, but, surprisingly, all died between 5 and 9 weeks of age with a seizure phenotype, which was confirmed by video and EEG recordings. Brain slice electrophysiology detected changes in the excitability of pyramidal cells and modified GABAergic inputs in the hippocampal CA1 region of LRRC8A bKO. LRRC8A-null hippocampi showed increased immunoreactivity of the astrocytic marker GFAP, indicating reactive astrogliosis. We also found decreased whole-brain protein levels of the GABA transporter GAT-1, the glutamate transporter GLT-1, and the astrocytic enzyme glutamine synthetase. Complementary HPLC assays identified reduction in the tissue levels of the glutamate and GABA precursor glutamine. Together, these findings suggest that VRAC provides vital control of brain excitability in mouse adolescence. VRAC deletion leads to a lethal phenotype involving progressive astrogliosis and dysregulation of astrocytic uptake and supply of amino acid neurotransmitters and their precursors.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Abbreviations: CA1-PCs, pyramidal cells of CA1 region; CNS, central nervous system; EEG, electroencephalogram; EPM, elevated plus maze; GAD, glutamate decarboxylase; GAT-1, GABA transporter type 1; GFAP, glial fibrillary acidic protein; GLT-1, glutamate transporter type 1; HIHS, heat-inactivated horse serum; HPLC, high-performance liquid chromatography; IgG, immunoglobulin G; IPSCs, inhibitory postsynaptic currents; KO, knockout [animal]; LRRC8, leucine-reach repeat-containing family 8; MBP, myelin-basic protein; MEM, minimal essential medium; MLC, megalencephalic leukoencephalopathy with subcortical cysts; MPFA, multiple-probability fluctuation analysis; OFT, open field test; PBS, phosphate-buffered saline; PTX, picrotoxin; PV, parvalbumin; TBS-T, Tris-buffered saline containing Tween-20; VGAT, vesicular GABA transporter; VRAC, volume-regulated anion channel.
Conflict of interest statement: The authors have declared that they have no conflicts of interest in connection with this article.
This is the revised and accepted version of the manuscript that will appear in FASEB Journal (https://faseb.onlinelibrary.wiley.com/doi/epdf/10.1096/fj.202002745R).