Author: Stephanie Dutchen

DNA diversity in the brain: Somatic mutations reveal a neuron’s history

neurons somatic mutations
Neurons are more like snowflakes–no two alike–than anyone realized.

Walt Whitman’s famous line, “I am large, I contain multitudes,” has gained a new level of biological relevance in neuroscience.

As we grow, our brain cells develop different genomes from one another, according to new research from Harvard Medical School and Boston Children’s Hospital. The study, published last week in Science, provides the most definitive evidence yet that somatic (post-conception) mutations exist in significant numbers in the brains of healthy people—about 1,500 in each of the neurons they sampled.

The finding confirms previous suspicions and lays the foundation for exploring the role of these non-inherited mutations in human development and disease. Already, the researchers have found evidence that the mutations occur more often in the genes a neuron uses most. And they been able to trace brain-cell lineages based on mutation patterns.

“This work is a proof of principle that if we had unlimited resources, we could actually decode the whole pattern of development of the human brain,” says co-senior investigator Christopher Walsh, MD, PhD, the HMS Bullard Professor of Pediatrics and Neurology and chief of the Division of Genetics and Genomics at Boston Children’s. “These mutations are durable memory for where a cell came from and what it has been up to. I believe this method will also tell us a lot about healthy and unhealthy aging as well as what makes our brains different from those of other animals.”

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Infecting bacteria show surprising genetic diversity; we may need to adapt too

New research may change the way we culture and treat infections. (Burkholderia cepacia complex, CDC/Wikimedia Commons)
New research may change the way we culture and treat infections. (Burkholderia cepacia complex, CDC/Wikimedia Commons)

Ed. note: A longer version of this story appeared on Harvard Medical School’s website.

A boy with cystic fibrosis develops a potentially deadly Burkholderia dolosa infection in his lungs. Various genetic mutations allow some bacterial strains to survive assaults from his immune system and antibiotics, while others perish. Eventually, the strongest mutant dominates the B. dolosa colony.

Right? Maybe not, say the authors of a new study. Examining sputum samples from infected patients, they found that dozens of different kinds of B. dolosa may coexist in that boy’s lungs—each adapting and surviving in different ways. The findings, published last month in Nature Genetics, warn of possible shortfalls in the way infections are currently cultured and treated.

“We found that when a pathogen like B. dolosa infects us, it diversifies. Many cells discover ways to survive, and these successful mutants coexist,” says senior author Roy Kishony, PhD, professor of systems biology at Harvard Medical School.

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