The Journal of Neuroscience, August 1, 1998, 18(15):5832-5838
Differential Regulation of Synaptic Vesicle Protein Genes by
Target and Synaptic Activity
Jeffery A.
Plunkett1,
Stephen A.
Baccus2, and
John L.
Bixby1, 2
1 Department of Molecular and Cellular Pharmacology and
2 Neuroscience Program, University of Miami School of
Medicine, Miami, Florida 33136
Differentiation of presynaptic nerve terminals involves changes in
gene expression; these may be regulated by synaptic transmission and/or
by contact with the target muscle. To gain insight into the control of
presynaptic differentiation, we examined the regulation by target and
synaptic activity of synaptic vesicle protein (SVP) genes in the chick
ciliary ganglion (CG). In the CG, two SVP genes, synaptotagmin I (syt
I) and synaptophysin II (syp II), are coordinately upregulated at the
time of target contact. To test the hypothesis that this upregulation
is induced by target contact, we examined mRNA levels of syt I and syp
II in CGs from embryos in which one eye had been removed before axon
outgrowth. As expected, target removal prevented the normal
upregulation of syt I mRNA in the deprived ganglion. In contrast, and
unexpectedly, syp II mRNA upregulation was not affected. The target
dependence of syt I upregulation was not attributable to nerve-muscle
transmission, because blockade of this transmission had no effect on
SVP mRNA levels. Surprisingly, blockade of synapses onto CG neurons
from the brain also did not affect syt I mRNA levels but increased levels of syp II mRNA. We conclude that contact with target induces upregulation of syt I mRNA, which is the case for spinal motor neurons.
However, the normal upregulation of syp II mRNA is not controlled by
the same signal(s). Instead, our results suggest that these two SVP
genes are differentially regulated, both by target contact and by
blockade of synaptic transmission.
Key words:
synaptotagmin; synaptophysin; ciliary ganglion; synapse
formation; atropine; hemicholinium-3
Copyright © 1998 Society for Neuroscience 0270-6474/98/18155832-07$05.00/0