GluN2A (GRIN2A) forms a di-heterotetramer with GluN1 (GRIN1). Based on the crystal structure of the rat GluN1:GluN2A (Grin1:Grin2a) NMDA receptor (Furukawa et al. 2005) and the Cryo-EM structure of the human GluN1:GluN2A (GRIN1:GRIN2A) NMDA receptor (Zhang et al. 2018), the tetramer includes 2 molecules of GluN1 and two molecules of GluN2A. GluN2A expression starts postnatally and GluN2A is highly expressed in adult brain (Monyer et al. 1992, Sheng et al. 1994).