Using a real-time PCR-based technique called MethyLight, we analyzed DNA methylation at 50 loci, most of them representing promoter CpG islands of genes expressed in the cerebral cortex; a portion of these genes is also implicated in cancer biology. Most of the cancerrelated genes included in this study show aberrant methylation in various types of neoplasia, including CNS tumors, and hence we were interested to monitor potential methylation changes within these genes during the course of normal brain development and aging. In mouse cerebral cortex, Dnmt3a NSC 136476 Hedgehog inhibitor expression remains detectable in adults, albeit at lower levels than observed during earlier periods of postnatal development; in contrast, Dnmt3b is found in murine CNS only during a narrow period of prenatal development. To find out when DNMT3a protein is expressed in the human cerebral cortex, we employed immunoblotting on cortical homogenates from fetal, child and adult samples. The present study examined DNA methylation changes for 50 genomic loci during the course of development, maturation and aging of the human cerebral cortex. The majority of loci showed significant age effects: eight loci showed a progressive increase in methylation that continued across the entire lifespan and another 18 loci were defined by a sharp rise within the first months or years after birth. We present direct evidence that, for a subset of loci, genomic DNA from differentiated cortical neurons undergoes methylation changes during the course of maturation and aging. In addition, one locus, MGMT, showed a stochastic accumulation in methylation starting around age 50, with potential Navitoclax implications for the tumor biology of astrogliomas, as discussed above. While DNA methylation changes related to development or aging were extremely robust in the present study, disease-associated changes, on the other hand, were surprisingly limited. Schizophrenia, a chronic psychiatric disease condition associated with psychosis and widespread cortical dysfunction in the absence of large-scale loss of neurons, was not associated with significant methylation changes in the present study. On the other hand, cases diagnosed with Alzheimer��s disease, which is defined by a neurodegenerative process in cerebral cortex and other brain regions, showed significant methylation changes in 2/50 loci. One locus, which is methylated in neurons was significantly less methylated in the DNA from Alzheimer cases compared to age-matched controls, possibly due to largescale loss of neurons associated with that disease. In addition, methylation of another locus was higher in the Alzheimer samples than in controls. Thus, the DNA methylation alterations in both genes appear to reflect an enhancement, or acceleration, of the age-associated changes that we observed in normal brain.