GluN1 (GRIN1) forms a di-heterotetrameric complex with GluN2C (GRIN2C) in heterologous expression systems. The tetramer includes two molecules of GluN1 and two molecules of GluN2C (Monyer et al. 1994). The stoichiometry in neurons remains to be determined. GluN2C expression starts late during embryonic development and is most prominent in cerebellum, olfactory bulb, and glial cells (Karavanova et al. 2007, Ravikrishnan et al. 2018, reviewed by Traynelis et al. 2010, Paoletti et al. 2013).