Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes

Berardo Rinaldi, Allan Bayat*, Linda G. Zachariassen, Jia Hui Sun, Yu Han Ge, Dan Zhao, Kristine Bonde, Laura H. Madsen, Ilham Abdimunim Ali Awad, Duygu Bagiran, Amal Sbeih, Syeda Maidah Shah, Shaymaa El-Sayed, Signe M. Lyngby, Miriam G. Pedersen, Charlotte Stenum-Berg, Louise Claudia Walker, Ilona Krey, Andrée Delahaye-Duriez, Lisa T. EmrickKrystal Sully, Chaya N. Murali, Lindsay C. Burrage, Julie Ana Plaud Gonzalez, Mered Parnes, Jennifer Friedman, Bertrand Isidor, Jérémie Lefranc, Sylvia Redon, Delphine Heron, Cyril Mignot, Boris Keren, Mélanie Fradin, Christele Dubourg, Sandra Mercier, Thomas Besnard, Benjamin Cogne, Wallid Deb, Clotilde Rivier, Donatella Milani, Maria Francesca Bedeschi, Claudia Di Napoli, Federico Grilli, Paola Marchisio, Suzanna Koudijs, Danielle Veenma, Emanuela Argilli, Sally Ann Lynch, Ping Yee Billie Au, Fernando Eduardo Ayala Valenzuela, Carolyn Brown, Diane Masser-Frye, Marilyn Jones, Leslie Patron Romero, Wenhui Laura Li, Erin Thorpe, Laura Hecher, Jessika Johannsen, Jonas Denecke, Vanda McNiven, Anna Szuto, Emma Wakeling, Vincent Cruz, Valerie Sency, Heng Wang, Juliette Piard, Fanny Kortüm, Theresia Herget, Tatjana Bierhals, Angelo Condell, Bruria Ben-Zeev, Simranpreet Kaur, John Christodoulou, Amelie Piton, Christiane Zweier, Cornelia Kraus, Alessia Micalizzi, Marina Trivisano, Nicola Specchio, Gaetan Lesca, Rikke S. Møller, Zeynep Tümer, Maria Musgaard, Benedicte Gerard, Johannes R. Lemke, Yun Stone Shi, Anders S. Kristensen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)


AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) mediate fast excitatory neurotransmission in the brain. AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal. Increasing numbers of GRIA3 missense variants are reported in patients with neurodevelopmental disorders (NDD), but only a few have been examined functionally. Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays. Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral. We collected detailed clinical data from 25 patients (from 23 families) harbouring 17 of these variants. All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25). Twelve patients had seizures, including focal motor (6/12), unknown onset motor (4/12), focal impaired awareness (1/12), (atypical) absence (2/12), myoclonic (5/12) and generalized tonic-clonic (1/12) or atonic (1/12) seizures. The epilepsy syndrome was classified as developmental and epileptic encephalopathy in eight patients, developmental encephalopathy without seizures in 13 patients, and intellectual disability with epilepsy in four patients. Limb muscular hypotonia was reported in 13/25, and hypertonia in 10/25. Movement disorders were reported in 14/25, with hyperekplexia or non-epileptic erratic myoclonus being the most prevalent feature (8/25). Correlating receptor functional phenotype with clinical features revealed clinical features for GRIA3-associated NDDs and distinct NDD phenotypes for loss-of-function and gain-of-function variants. Gain-of-function variants were associated with more severe outcomes: patients were younger at the time of seizure onset (median age: 1 month), hypertonic and more often had movement disorders, including hyperekplexia. Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances. Loss-of-function and gain-of-function variants were disease-causing in both sexes but affected males often carried de novo or hemizygous loss-of-function variants inherited from healthy mothers, whereas affected females had mostly de novo heterozygous gain-of-function variants.

Original languageEnglish
Pages (from-to)1837-1855
Number of pages19
JournalBrain : a journal of neurology
Issue number5
Publication statusPublished - 1 May 2024

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