GRIN2B and schizophrenia: Single nucleotide or dinucleotide-repeated polymorphisms of the NMDAR subunit genes, such as NR1 (GRIN1), NR2A (GRIN2A), and NR2B (GRIN2B), increase susceptibility to schizophrenia (Ohtsuki et al., 2001; Rice et al., 2001; Miyatake et al., 2002; Itokawa et al., 2003; Iwayama-Shigeno et al., 2005; Qin et al., 2005; Martucci et al., 2006; Tang et al., 2006; Zhao et al., 2006).