Disruption of grin2A, an epilepsy-associated gene, produces altered spontaneous swim behavior in zebrafish

N-methyl-D-aspartate receptors (NMDARs) control synaptic plasticity and brain development in a manner determined by receptor subunit composition. Pathogenic variants in GRIN2A gene, encoding the NMDAR GluN2A subunit, can cause gain or loss of function of receptors containing the affected subunit, and are associated with intellectual disability and epilepsy in patients. While in-vitro studies of recombinant receptors have yielded some insights, animal experimental models are essential to better understand the relationship between the molecular pathology of the variants and the disease. Here we introduce a zebrafish model of GluN2A loss of function to study system-level effects of zebrafish grin2Aa and grin2Ab gene deletion. Our electrophysiological analysis revealed functional differences between receptors containing zebrafish GluN2Aa/b and GluN2Bb paralogs comparable to mammalian receptors containing GluN2A vs. GluN2B subunits. Both grin2Aa^-/- and grin2Ab^-/- , as well as double-knockout grin2A^-/- zebrafish larvae showed increased locomotor activity in a novel environment. Proteomic analysis suggested that the relative proportion of GluN2B-containing NMDARs may be increased in grin2A mutant fish. Our results highlight fundamental similarities between zebrafish and mammalian NMDAR signaling and validate the use of zebrafish as a model organism to study the neurodevelopmental role of NMDARs. The newly created transgenic zebrafish strains complement the rodent models of GluN2A loss of function and can be used for high-throughput testing of pharmacological or genetic treatment strategies for patients with GRIN2A gene variants.Significance Statement N-methyl-D-aspartate receptors (NMDARs), critical for brain development and synaptic plasticity, are regulated by subunit composition. Pathogenic variants in the GRIN2A gene, encoding the GluN2A subunit, are linked to epilepsy and intellectual disability through altered receptor function. To explore system-level consequences of GluN2A loss, we developed zebrafish models lacking grin2Aa and grin2Ab genes. These mutants exhibited increased locomotor activity and possibly altered receptor subunit ratios, resembling features seen in mammalian GluN2A deficiency. Electrophysiological analysis confirmed functional distinctions between GluN2A- and GluN2B-containing zebrafish receptors, paralleling mammalian NMDAR properties. These results validate zebrafish as a model for GRIN2A-related disorders and establish a foundation for high-throughput screening of therapeutic strategies, complementing existing rodent models.