brain plasticity: gene content of each neuron can vary (Introduction)

by David Turell , Sunday, June 26, 2016, 23:44 (3073 days ago) @ David Turell

To make the brain as responsive as possible to our needs each neuron can vary its own instructions:-http://www.the-scientist.com/?articles.view/articleNo/46399/title/Single-Cell-RNA-Sequencing-Reveals-Neuronal-Diversity/&utm_campaign=NEWSLETTER_TS_The-Scientist-Daily_2016&utm_source=hs_email&utm_medium=email&utm_content=30975475&_hsenc=p2ANqtz--bFYZlFXBRhtY3gEshC8Bbq3WER9bcpJK9Gak9VTw2Sa5HbJB3b8vJLZdI7FDTTnbCSYSOQwIaOOqJh5gw7nif1PvRRg&_hsmi=30975475/-"Neurons within a single brain can differ from one another in genomic content—a phenomenon known as mosaicism. But the extent to which those differences are reflected in gene expression has remained uncertain, in large part because of the difficulty associated with analyzing transcription in individual cells. Now, a team led by researchers at the Scripps Research Institute in La Jolla, California, and the University of California, San Diego (UCSD), has developed a high-throughput pipeline to analyze the transcriptomes of thousands of single neuronal nuclei, revealing considerable variation in gene expression across the human cerebral cortex.-***-"Previous attempts to resolve differences in gene expression among neurons have been limited in scope by the small samples obtainable from fresh brains, and by the challenge of physically disentangling individual cells from one other. “All these neurons in the human adult brain, they're highly, highly connected,” explained UCSD's Kun Zhang, a bioengineer and collaborator on the National Institute of Health's Single Cell Analysis Program (SCAP). “It's very difficult to dissociate individual neurons from human brains.”-***-"By sequencing messenger RNA (mRNA) transcripts within these nuclei, the team generated 3,227 single-cell transcriptome datasets across the six regions: “more than an order of magnitude more than what's been looked at previously,” Chun told The Scientist. Not only did these datasets identify cells as either inhibitory or excitatory (consistent with previous work in mice), they also revealed 16 distinct neuronal subtypes divided between these two categories that tended to be localized in one or a few Brodmann areas, indicating that the composition of neuronal types varies among regions of the brain.-“'One of the major findings is that the composition in the visual cortex is very different from the other five areas that we sampled,” Zhang said, adding that further transcriptome differences were observable within subtypes as well as between them. “With these subtypes, we can start to ask, ‘What are the differences across these six brain areas, and do particular subtypes contribute to these differences?"-Comment: This is a human study. At some point ape brains will have this same study, and I can guess the result: no where near the variability. This is part of the reason why our brains are so helpful to our needs. One can only wonder how this developed in evolution without purposeful planning.