IREB2 and nicotine dependence: In this study, METH-induced behavioral sensitization was accompanied by increased IREB2 expression in the NAc, whereas the nicotine addiction susceptibility gene IREB2 was identified in a genome-wide association study (GWAS) of nicotine-addicted populations [42], and another study demonstrated that Ireb2−/− mice had decreased locomotor activity [43].