Functional Investigation of a GRIN2A Variant Associated with Rolandic Epilepsy

• Published in: Neuroscience bulletin Vol. 34; no. 2; pp. 237 - 246
• Main Authors: Xu, Xing-Xing, Liu, Xiao-Rong, Fan, Cui-Ying, Lai, Jin-Xing, Shi, Yi-Wu, Yang, Wei, Su, Tao, Xu, Jun-Yu, Luo, Jian-Hong, Liao, Wei-Ping
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.04.2018; Springer
• Subjects: Adolescent; Anatomy; Anesthesiology; Aspartate; Biomedical and Life Sciences; Biomedicine; Epilepsy; Epilepsy, Rolandic - genetics; Genetic aspects; Glutamate; Human Physiology; Humans; Investigations; Lamotrigine; Male; Methyl aspartate; Mutation; Neurology; Neurophysiology; Neurosciences; Original; Original Article; Pain Medicine; Receptors, N-Methyl-D-Aspartate - genetics; T cells; NMDA receptors; Epilepsy; Mutation; GRIN2A
• ISSN: 1673-7067; 1995-8218
• DOI: 10.1007/s12264-017-0182-6

N-methyl-D-aspartate receptors (NMDARs), a subtype of glutamate-gated ion channels, play a central role in epileptogenesis. Recent studies have identified an increasing number of GRIN2A (a gene encoding the NMDAR GluN2A subunit) mutations in patients with epilepsy. Phenotypes of G RIN2A mutations include epilepsy-aphasia disorders and other epileptic encephalopathies, which pose challenges in clinical treatment. Here we identified a heterozygous GRIN2A mutation (c.1341T>A, p.N447K) from a boy with Rolandic epilepsy by whole-exome sequencing. The patient became seizure-free with a combination of valproate and lamotrigine. Functional investigation was carried out using recombinant NMDARs containing a GluN2A-N447K mutant that is located in the ligand-binding domain of the GluN2A subunit. Whole-cell current recordings in HEK 293T cells revealed that the N447K mutation increased the NMDAR current density by ~1.2-fold, enhanced the glutamate potency by 2-fold, and reduced the sensitivity to Mg 2+ inhibition. These results indicated that N447K is a gain-of-function mutation. Interestingly, alternative substitutions by alanine and glutamic acid at the same residue (N447A and N447E) did not change NMDAR function, suggesting a residual dependence of this mutation in altering NMDAR function. Taken together, this study identified human GluN2A N447K as a novel mutation associated with epilepsy and validated its functional consequences in vitro . Identification of this mutation is also helpful for advancing our understanding of the role of NMDARs in epilepsy and provides new insights for precision therapeutics in epilepsy.