Source: The Society for Neuroscience
Date: November 2001
Links: www.sfn.org
www.newscientist.com
San Diego, US, November 2001
"Magic ingredient" for neural stem cells revealed
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 (november 2001).
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