The Journal of Neuroscience, January 15, 2000, 20(2):736-748
Expression of Neurotrophin-3 (NT-3) and Anterograde Axonal
Transport of Endogenous NT-3 by Retinal Ganglion Cells in Chick
Embryos
Christopher S.
von Bartheld and
Rafal
Butowt
Department of Physiology and Cell Biology, University of Nevada
School of Medicine, Reno, Nevada 89557
Anterograde axonal transport of neurotrophins has been demonstrated
recently, but to date such transport has only been shown for
brain-derived neurotrophic factor and no other endogenous neurotrophin. Endogenous neurotrophin-3 (NT-3) protein is present in
the ganglion cell layer of the chicken retina, as well as the superficial layers of the optic tectum. NT-3 immunolabel in these tectal layers is largely reduced or abolished after treatment of the
eye with colchicine or monensin, demonstrating that endogenous NT-3 is
transported to the optic tectum by retinal ganglion cells (RGCs).
Reverse transcription-PCR analysis of RGCs purified to 100% shows that
RGCs, but not tectal cells, express NT-3 mRNA. Blockade of the
intercellular transfer of NT-3 within the retina does not reduce the
anterograde transport of endogenous NT-3 to the tectum, indicating that
a major fraction of the anterogradely transported NT-3 is produced by
RGCs rather than taken up from other retinal cells. Immunolabel for the
neurotrophin receptor p75, but not trkB or trkC, in the superficial
tectum coincides with the NT-3 label. The p75 label in the neuropil of
superficial tectal layers is largely reduced or eliminated by injection
of monensin in the eye, indicating that p75 protein is exported along RGC axons to the retinotectal terminals and may act as a neurotrophin carrier. These results show that NT-3 is produced by RGCs and that some
of this NT-3 is transported anterogradely along the axons to the
superficial layers of the tectum, possibly to regulate the survival,
synapse formation, or dendritic growth of tectal neurons.
Key words:
anterograde transport; NT-3; BDNF; retina; optic tectum; p75 neurotrophin receptor; neurotrophic factor; visual system; RT-PCR
Copyright © 2000 Society for Neuroscience 0270-6474/00/202736-13$05.00/0
Previous Article | Next Article
