Abstract | OBJECTIVE: METHODS: We conducted whole-exome sequencing of patients with myoclonic atonic epilepsy (MAE) and characterized the seizure phenotypes and EEG patterns. We studied the protein stability and structural changes with homology modeling and machine learning tools. We characterized the function and trafficking of the mutant GAT-1 with 3H radioactive GABA uptake assay and confocal microscopy. We utilized different models including a knockin mouse and human astrocytes derived from induced pluripotent stem cells (iPSCs). We focused on astrocytes because of their direct impact of astrocytic GAT-1 in seizures. RESULTS: We identified four novel SLC6A1 variants associated with MAE and 2 to 4 Hz spike-wave discharges as a common EEG feature. Machine learning tools predicted that the variant proteins are destabilized. The variant protein had reduced expression and reduced GABA uptake due to endoplasmic reticular retention. The consistent observation was made in cortical and thalamic astrocytes from variant-knockin mice and human iPSC-derived astrocytes. The Slc6a+/A288V mouse, representative of MAE, had increased 5-7 Hz spike-wave discharges and absence seizures. INTERPRETATION: SLC6A1 variants in various locations of the protein peptides can cause MAE with similar seizure phenotypes and EEG features. Reduced GABA uptake is due to decreased functional GAT-1, which, in thalamic astrocytes, could result in increased extracellular GABA accumulation and enhanced tonic inhibition, leading to seizures and abnormal EEGs.
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Authors | Felicia Mermer, Sarah Poliquin, Shuizhen Zhou, Xiaodong Wang, Yifeng Ding, Fei Yin, Wangzhen Shen, Juexin Wang, Kathryn Rigsby, Dong Xu, Taralynn Mack, Gerald Nwosu, Carson Flamm, Matthew Stein, Jing-Qiong Kang |
Journal | Neurobiology of disease
(Neurobiol Dis)
Vol. 172
Pg. 105810
(10 01 2022)
ISSN: 1095-953X [Electronic] United States |
PMID | 35840120
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural)
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Copyright | Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved. |
Chemical References |
- GABA Plasma Membrane Transport Proteins
- SLC6A1 protein, human
- gamma-Aminobutyric Acid
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Topics |
- Animals
- Astrocytes
(metabolism)
- Epilepsies, Myoclonic
(genetics)
- Epilepsy, Absence
- GABA Plasma Membrane Transport Proteins
(genetics, metabolism)
- Humans
- Mice
- Seizures
(complications, genetics)
- gamma-Aminobutyric Acid
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