Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant

Kohei Hamanaka, Keita Miyoshi, Jia Hui Sun, Keisuke Hamada, Takao Komatsubara, Ken Saida, Naomi Tsuchida, Yuri Uchiyama, Atsushi Fujita, Takeshi Mizuguchi, Benedicte Gerard, Allan Bayat, Berardo Rinaldi, Mitsuhiro Kato, Jun Tohyama, Kazuhiro Ogata, Yun Stone Shi, Kuniaki Saito, Satoko Miyatake, Naomichi Matsumoto*

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GRIA3 at Xq25 encodes glutamate ionotropic receptor AMPA type 3 (GluA3), a subunit of postsynaptic glutamate-gated ion channels mediating neurotransmission. Hemizygous loss-of-function (LOF) variants in GRIA3 cause a neurodevelopmental disorder (NDD) in male individuals. Here, we report a gain-of-function (GOF) variant at GRIA3 in a male patient. We identified a hemizygous de novo missense variant in GRIA3 in a boy with an NDD: c.1844C > T (p.Ala615Val) using whole-exome sequencing. His neurological signs, such as hypertonia and hyperreflexia, were opposite to those in previous cases having LOF GRIA3 variants. His seizures and hypertonia were ameliorated by carbamazepine, inhibiting glutamate release from presynapses. Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics. A fly line expressing a human GluA3 mutant possessing our variant and the Lurcher variant, which makes ion channels leaky, showed developmental defects, while one expressing a mutant possessing either of them did not. Collectively, these results suggest that p.Ala615Val has GOF effects. GRIA3 GOF variants may cause an NDD phenotype distinctive from that of LOF variants, and drugs suppressing glutamatergic neurotransmission may ameliorate this phenotype. This study should help in refining the clinical management of GRIA3-related NDDs.

TidsskriftHuman Genetics
Sider (fra-til)283-293
StatusUdgivet - feb. 2022

Bibliografisk note

Funding Information:
The authors thank Ms. Kaori Takabe, Mr. Takabumi Miyama, Ms. Nobuko Watanabe, Ms. Mai Sato, and Ms. Sayaka Sugimoto at Department of Human Genetics, Yokohama City University Graduate School of Medicine, and S. Kondo at Tokyo University of Science for their technical assistance, and the Drosophila Genetic Resource Center, Kyoto Institute of Technology, for providing the fly strains. They are also grateful to Edanz ( ) for editing the English text of a draft of this manuscript. This work was supported by Japan Agency for Medical Research and Development (AMED) [JP20ek0109486, JP21ek0109549, JP21cm0106503, and JP21ek0109493 to N.M.; and JP19ek0109288 to K. Saito]; Japan Society for the Promotion of Science (JSPS) KAKENHI [JP20K16932 to K. Hamanaka, JP 20K17428 to N.T., JP 21k15097 to Y.U., JP20K17936 to A.F., and JP20K07907 to S.M.]; and an intramural Grant of Yokohama City University (to K. Hamanaka).

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.


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