Several clinical trials have been conducted to assess the efficacy of agonists targeting both mGlu2 and mGlu3 receptor subtypes to treat schizophrenia symptoms (Patil et al., 2007; Kinon et al., 2011; Adams et al., 2013; Stauffer et al., 2013), with varying success. The gene discussed is GRM2; the disease is schizophrenia.