GRIA3, located on the X-chromosome, encodes the GluA3 subunit of the AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptor. AMPA receptors mediate fast excitatory neurotransmission in the brain, with GRIA3-encoded subunits contributing to the formation of these receptors, which are crucial for synaptic plasticity and normal brain function [1,2,3].

Functional studies on GRIA3 variants in patients with neurodevelopmental disorders (NDD) have revealed significant insights. Electrophysiological assays on 43 rare missense and one frameshift GRIA3 variants from NDD patients showed that 31 variants altered receptor function, presenting loss-of-function or gain-of-function properties [1]. Loss-of-function variants were associated with features like older age at seizure onset (median age: 16 months), hypotonia, and sleeping disturbances, while gain-of-function variants led to more severe outcomes such as younger age at seizure onset (median age: 1 month), hypertonia, and more frequent movement disorders [1]. Additionally, a missense variant c.2477G > A; p.(Gly826Asp) in affected male patients was found to decrease current response to agonists and reduce cell-surface expression, suggesting pathogenicity via a loss-of-function mechanism, and was associated with an exaggerated startle reflex, chorea, and multifocal myoclonus [4].

In conclusion, GRIA3 is essential for normal brain function through its role in AMPA receptor assembly. Research on GRIA3 variants in patients has highlighted its significance in neurodevelopmental disorders, with loss-of-function and gain-of-function variants leading to distinct phenotypes. Understanding these relationships can potentially contribute to better diagnosis and treatment strategies for related NDDs.