The enormous
complexity of nervous system function results from interactions
between a vast number of different neuronal cell types.
To begin addressing how this diversity is generated,
we have been studying how sympathetic neurons develop
from uncommitted embryonic precursor cells.
We have shown
that the neurotrophic factors nerve growth factor (NGF)
and neurotrophin-3 (NT-3) act sequentially on these
developing neurons to support their survival during
differentiation. Other factors such as fibroblast growth
factor act as initial triggers of this differentiation
process.
Taken together,
these studies have demonstrated how precursor cells
can develop under the influence of local factors (NT-3
and FGF), and eventually be supported by factors (NGF)
produced by distant targets of sympathetic innervation.
These developmental switches in factor responsiveness
are likely to represent a general mechanism of nervous
system development.
