Reversing DNA methylation: new insights from neuronal activity-induced Gadd45b in adult neurogenesis.

Neurogenesis in the adult mammalian brain involves activity-dependent expression of genes critical for the proliferation of progenitors and for neuronal maturation. A recent study suggests that the stress response gene Gadd45b (growth arrest and DNA-damage-inducible protein 45 beta) can be transiently induced by neuronal activity and may promote adult neurogenesis through dynamic DNA demethylation of specific gene promoters in adult hippocampus. These results provide evidence supporting the provocative ideas that active DNA demethylation may occur in postmitotic neurons and that DNA methylation-mediated dynamic epigenetic regulation is involved in regulating long-lasting changes in neural plasticity in mammalian brains.