By Robert Martone
We normally think that every cell in our body contains the same genome, the complete set of genetic information that makes up the biological core of our individuality. However, there are exceptions where the body contains cells that are genetically different. This happens in cancers, of course, which arise when mutations create genetically distinct cells. What most people do not realize, however, is that the brain has remarkable genetic diversity, with some studies suggesting there may be hundreds of mutations in each nerve cell. In the developing brain, mutations and other genetic changes that occur while brain cells divide are passed down to a cluster of daughter cells. As a result, the adult brain is composed of a mosaic of genetically distinct cell clusters.
We know that the activity and organization of the brain changes in response to experience. Memories and learning are reflected in the number and strength of connections between nerve cells. We also know that the brain is genetically mosaic, but a new study makes a remarkable connection between experience and the genetic diversity of the brain. It suggests that experience can change the DNA sequence of the genome contained in brain cells. This is a fundamentally new and unexplored way in which experience can alter the brain. It is of great scientific interest because it reveals the brain to be pliable, to its genetic core, in response to the world.
The genome is the molecular signature of identity. The sequence of DNA contained in our genomes distinguishes each of us as unique individuals, and changes in that sequence are relatively rare. Genomic changes typically arise from rare errors during cell replication, or from exposure to carcinogens or radiation. Here, experience has an equally powerful capacity to change the genome, but only in cells of the brain. The care that a newborn receives in early life can have profound effects on psychological and intellectual growth. Attentive nurturing, feeding and grooming can reduce stress and anxiety and enhance psychological well-being. On the other hand, indifference can lead to increased anxiety and impaired psychological adjustment. This study reveals that one way the quality of early care could cause lifelong changes in behavior is by changing the brain’s genetic nature.
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