New research by a team at the Medical Research Council's
National Institute for Medical Research (NIMR; now part of
the Francis Crick Institute) explores the mechanisms by
which neural stem cells are generated and produce their offspring.
Neural stem cells are a type of brain cell that continuously
divides and produces new and different nerve cells, or
neurons.
Animal brains are organised into different areas with distinct
functions, each made up of many diverse types of neurons.
Scientists had shown that this diversity is caused by patterning of
neural stem cells in different parts of the brain, but did not know
whether other mechanisms also could
contribute.
Now, Holger Apitz and Iris Salecker of NIMR have identified a
new strategy for generating neurons in the brains of the fruit fly
Drosophila.
They studied the fly's visual system. It was already known that
- as in many other parts of the fly brain - neurons are typically
produced by cells called neuroblasts, the fly equivalents of neural
stem cells. When these divide, each neuroblast produces one new
copy of itself and one other cell that divides to generate
neurons.
However, the scientists identified one region in the fly's
visual system that uses a different strategy to generate its neural
stem cells and neurons. This involves the production of precursor
cells that move from one region to another before developing into
neural stem cells and giving rise to neurons. This strategy is
remarkably similar to a process observed in the mammalian brain,
and therefore may also occur in humans.
The scientists' discovery means that future studies will be able
to use this region of the Drosophila brain as a model to understand
what happens in mammalian brains. In the long term, this could help
to find out what may go wrong in brain disorders caused by
developmental defects and to work towards ways to treat such
defects.
Dr Salecker said: "Since some of the observed molecular and
cellular mechanisms appear to be shared between the fly visual
system and mammalian brains, we hope that our findings, in
conjunction with the powerful genetic toolbox of Drosophila, can be
used as a start to systematically identify the genes controlling
the production of neural stem cells and neurons by this particular
developmental strategy in the future".
The paper, A region-specific neurogenesis mode requires migratory progenitors
in the Drosophila visual system, is published in Nature
Neuroscience.