The new development is a study in which the scientists worked with embryonic mouse brains. It may simplify the isolation of stem cells not only from brain, but also other body tissues, say the researchers.
The researchers say that they have identified a specific protein "signal", which appears to prevent neural stem cells from taking their first step towards becoming neurons. They say that this sort of protein might be used to rebuild a damaged nervous system.
"Stem cells don't instantly convert into functional adult tissue. They undergo a stepwise maturation where they gradually shed their stem cell properties," Nature magazine quoted study author Dr. Nicholas Gaiano, assistant professor at the Institute for Cell Engineering, as saying.
The first step turns stem cells into "progenitor" cells by dictating the mechanism through which signals downstream of the Notch protein, which regulates stem cells in many different tissues, are transmitted. One well-known target of Notch is a protein called CBF1.
In order to study Notch signalling further, Dr. Gaiano and his colleagues created genetically engineered mouse embryos that glow green when CBF1 is turned on.
The researchers found that during brain development some of the brain cells, generally thought to be neural stem cells, stopped glowing. It was an indication that the CBF1 protein was no longer active in them. A closer look revealed that the cells that went dark were in fact no longer true neural stem cells, which could form all major brain cell types, but instead had aged into progenitor cells, which formed mostly neurons.
The researchers then knocked out the CBF1 protein in neural stem cells so as to test whether it was the critical switch. They found that the knockout got the stem cells to rapidly convert to progenitor cells. "However, if we activated the CBF1 protein in progenitor cells we couldn't get them to shift back into stem cells. So whatever happens biochemically once CBF1 is turned off seems to create a one-way street," says Dr. Gaiano.
In another study, Dr. Gaiano and his colleagues have also found that CBF1 signalling may play the same role in blood stem cells, indicated that the new discovery might be a general "switch" distinguishing stem cells from progenitors in many different tissues.