A team of San Diego scientists has developed a new way of looking deep into the human brain. By zooming inside individual cells from different brain regions, researchers found diversity in how different neurons transcribe their DNA.
For a study published in the journal Science on Thursday, the scientists looked at the genes expressed in different neurons from six different regions of a postmortem human brain. Based on the genetic activity found within these cells, they were able to identify 16 different subtypes of neurons.
"This was a chance to look at single neurons in a way that really hadn't been possible before on a large scale," said Jerold Chun, a neuroscientist at the Scripps Research Institute in La Jolla and a senior author of the study.
"We've known for many years that there are huge differences in the way neurons look and how they're connected," he said. "But now we can actually look at some of the molecules that are responsible for that."
Chun says understanding diversity among neurons will be important for understanding diseases like Alzheimer's and Parkinson's.
Genetic studies of human brain cells have been done in the past, but they've focused on isolated chunks of surgically removed brain. Chun says that's like looking at a small American neighborhood and assuming it represents all of the diversity found throughout the U.S.
So far, the technique has only been applied to one brain donated by a 51-year-old woman free of neurodegenerative disease. Chun hopes to create a reference map of the genetic diversity found in a typical, healthy brain. That will require probing a lot more regions within a lot more human brains.
Scientists from UC San Diego and the local gene sequencing company Illumina also worked on the study.
"We couldn't have done it without this incredible collaboration," Chun said. "I think that's one of the great strengths of the community here."
