In a late-onset familial AD (FAD) mouse model, H3K9 dimethylation (H3K9me2) and histone methyltransferase 1 (EHMT1) and EHMT2 were significantly increased in the prefrontal cortex, a key cognitive region in AD (Zheng et al., 2019). The gene discussed is EHMT1; the disease is Alzheimer disease.