Brain metabolic DNA in memory processing and genome turnover.

Sophisticated methods are currently used to investigate the properties of brain DNA and clarify its role under physiological conditions and in neurological and psychiatric disorders. Attention is now called on a DNA fraction present in the adult rat brain that is characterized by an elevated turnover and is not involved in cell division or DNA repair. The fraction, known as brain metabolic DNA (BMD), is modulated by strain, stress, circadian oscillations, exposure to enriched or impoverished environment, and notably by several training protocols and post-trial sleep. BMD is frequently localized in glial cells but is also present in neurons, often in the perinucleolar region. Its distribution in repetitive and non-repetitive DNA fractions shows that BMD differs from native DNA and that in learning rats its profile differs from that of control rats. More detailed knowledge of the molecular, cellular, and time-dependent BMD features will be necessary to define its role in memory acquisition and processing and in the pathogenesis of neurologic disorders.