Among mGlu receptors, growing evidence suggests that group II mGlu receptors (mGlu2 and mGlu3 receptors), which have major roles in the regulation of glutamatergic transmission within the cortical and limbic systems (Wright et al., 2013), may serve as potential therapeutic targets for neuropsychiatric disorders, including schizophrenia (Chaki, 2010; Stansley and Conn, 2018), depression (Chaki, 2017), anxiety (Swanson et al., 2005), and cognitive impairment (Kim et al., 2014). The gene discussed is GRM2; the disease is major depressive disorder.