For example, a recent study showed that expression of Dnmt1 mRNA is increased in prefrontal cortical GABAergic neurons of schizophrenia patients with decreased GAD67 level [42]; while nicotine injections for 4 days decreased Dnmt1 mRNA and protein with increased GAD67 expression in the mouse frontal cortex [49]. The gene discussed is GAD1; the disease is schizophrenia.