< http://www.newscientist.com > "Magic ingredient" for neural stem cells revealed
17:03 13 November 01 Emma Young, San Diego
Vital new clues to what makes certain cells in the brain act as neural stem cells have been uncovered. The researchers say their work will boost research into creating new neurons to repair damaged brains.
Recent experiments have provided strong evidence that in the developing fetal brain, a subsection of a group of cells called radial glial cells act as neural stem cells, giving rise to neurons. Related cells in the adult brain called astrocytes can also act as neural stem cells.
But what gives certain radial glial cells and a very small number of astrocytes in two discrete adult brain areas their stem cell capabilities has been a mystery.
Now a team at the Max-Planck Institute of Neurobiology in Germany has uncovered a key molecule involved. When this molecule was added to astrocytes that do not normally act as stem cells, they started producing new neurons.
"Astrocytes that naturally act as stem cells are a very rare cell type - but if we understand more about the differences between 'normal' astrocytes and neurogenic astrocytes, we could potentially use the ones found throughout the brain for neural replacements," says researcher Magdalena Götz.
"Magic ingredient"
Götz and her colleagues first worked on mouse radial glial cells, which until very recently were thought to be simply "helper" cells, guiding the growth of neurons in the fetal brain.
The team studied transcription factors - molecules that regulate which genes are transcribed and then translated into proteins. They found that radial glial cells that lacked a functional form of a transcription factor called Pax6 could not generate neurons. But when Pax6 was introduced into glial precursor cells, these cells started to produce neurons.
Perhaps more importantly, the team found that the introduction of Pax6 into mouse astrocytes had the same effect. This raises the prospect of using "normal" astrocytes taken from a patient with brain damage to make new neurons, for use in treatment.
Finding molecular markers that indicate whether a radial glial cell can act as a stem cell or not will also help researchers "purify" samples, says Götz.
In the dark
The identification of certain radial glial cells and certain astrocytes as neural stem cells has a huge impact, say researchers in the field.
"Before this, we were pretty much working in the dark about what these stem cells in the brain were," says Gordon Fishell of New York University. "Now we know what cells we should be going after in the brain if we want to get cells with stem cell-like properties." Because radial glial cells guide the growth of neural cells in the developing brain, it is also possible that they could be used to guide treatment cells to their target, says Arnold Kriegstein of Columbia University, New York.
Götz presented the new research at the Society for Neuroscience annual conference in San Diego.
17:03 13 November 01