"Thousands of Mutations Accumulate in the Human Brain Over a Lifetime"

"Cells of the human body acquire mutations over time, whether because of errors introduced during DNA replication or damage incurred during transcription and other cellular processes. But, until recent technological developments enabled whole genome sequencing from the miniscule quantities of DNA found inside single cells or small clones of the same cell, investigating the nature and extent of such somatic mutations—and the resulting tissue mosaicism—was practically impossible.

Within the now burgeoning field of somatic mutation analyses, the brain is a particular area of interest. That’s because unlike organs such as the skin and gut where cells are replaced daily, the brain’s neurons, once established in the fetus, for the most part stick around for life. Somatic mutations in these cells, then, could affect brain function, behavior, and the propensity for disease long-term. Indeed, it’s thought that such mutations could influence the development of diseases such as schizophrenia, autism, and Tourette’s, which have unclear etiologies, says Yale School of Medicine’s Flora Vaccarino who authored one of the studies... 

The researchers found that a neuron “starts with around 600 mutations” in an infant, “and the mutations accumulate about one every two weeks, so that by the time a neuron is 80 years old it has about 2,400 or so,” says Christopher Walsh of Harvard Medical School and Boston Children’s Hospital who authored the study. “In general, our numbers pick up right where [Vaccarino’s] leave off,” he says... 

“About one percent of the mutations are likely to be functional in the sense that they disrupt a protein,” says Walsh, “so by the time you’re 80 years old there’s about one in a thousand neurons that has had a gene essentially knocked out.” Mutation accumulation could therefore be “a reasonable model for how age-related cognitive decline might come about,” he says."

https://www.the-scientist.com/?articles.view/articleNo/51118/title/Thousands-of-Mutations-Accumulate-in-the-Human-Brain-Over-a-Lifetime/