Developmental Pb exposure not only altered DNA methylation in both specific gene level and global genome level in brain of Alzheimer’s disease model [25–28], but also could affect the expression of DNA methyltransferase 1(DNMT1) and DNA methyltransferase 3a (DNMT3a) in hippocampus [29]. This evidence concerns the gene DNMT3A and early-onset autosomal dominant Alzheimer disease.