Sent: 7/23/2011 5:38:45 P.M. Central Daylight Time
Subj: Human Skin Cells Converted Into Neurons
Human Skin Cells Converted Into NeuronsMain Category: Neurology / Neuroscience
Also Included In: Stem Cell Research
Article Date: 14 Jul 2011 - 3:00 PDT
The addition of two particular gene snippets to a skin cell's usual genetic material is enough to turn that cell into a fully functional neuron, report researchers from the Stanford University School of Medicine. The finding, published online July 13 in Nature, is one of just a few recent reports of ways to create human neurons in a lab dish.
The new capability to essentially grow neurons from scratch is a big step for neuroscience research, which has been stymied by the lack of human neurons for study. Unlike skin cells or blood cells, neurons are not something that's easy for a living human to donate for research.
"A major problem in neurobiology has been the lack of a good human model," said senior author Gerald Crabtree, MD, professor of pathology and of developmental biology. "Neurons aren't like blood. They're not something people want to give up."
Generating neurons from easily accessible cells, such as skin cells, makes possible new ways to study neuronal development, model disease processes and test treatments.
It also helps advance the effort, still in its infancy, to replace damaged or dead neurons with new ones.
Before succeeding at turning skin cells straight into neurons, scientists had discovered two years ago that they could get similar results if they transformed the skin cell first into a stem cell and then coaxed the stem cell into becoming a neuron. But Crabtree's new study and two studies by others show it's possible to go straight from skin cell to neuron without the stem-cell pit stop.
Crabtree's study is unique among the efforts because of the surprising identity of the molecules that nudged the cells to switch - short chains of genetic material called microRNA, best known for their ability to bind to specific genetic transcripts to turn off their activity.
"In this case, though, they're playing an instructive role," Crabtree said.
The discovery of the microRNAs' ability to switch the cells came to light when Andrew Yoo, PhD, then a postdoctoral researcher in Crabtree's lab (now on the faculty of Washington University in St. Louis), was trying to better understand what makes neural stem cells move on to become mature neurons. He found that two microRNAs, miR-9/9* and miR-124, trigger it by controlling a molecular machine (called the BAF chromatin remodeling complex) that shapes chromosomes so they'll direct the cell to remain a stem cell.
"When the microRNAs bind to one subunit of this 13-membered complex they turn this function off, and the cells begin to grow up and connect to one another - that is, they become mature, functioning neurons," said Crabtree. After they published this in Nature in 2009, Yoo went on to try to understand how the two microRNAs functioned. One way he did this was to watch what happened when he introduced them into cells that normally lacked them.
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