As observed in the dentate gyrus, developmental arsenic exposure significantly increases levels of H3K4me3 in (A) the adult male frontal cortex with concurrent increased protein expression of (B) MLL, the histone methyltransferase responsible for trimethylation of H3K4, and decreased protein expression of (C) KDM5B, the demethylase that removes methyl groups from H3K4. Unlike the observations in the dentate gyrus, DAE does not impact (D) H3K4me3 levels or protein expression of (E) MLL or (F) KDM5B in the adult female frontal cortex. *p<.05; **p<.01