Journal of Neuroscience, Vol 13, 387-401, Copyright © 1993 by Society for Neuroscience
The expression of the protein p68/70 within the goldfish visual system suggests a role in both regeneration and neurogenesis
GR Wilmot, PA Raymond and BW Agranoff
Neuroscience Program, University of Michigan, Ann Arbor 48104.
Previous attempts to characterize the molecular events that support
successful regeneration of axotomized goldfish retinal ganglion cells
(RGCs) have led to the discovery of an acidic protein doublet in retina
that displays an increased incorporation of 35S-methionine following
axotomy, and is known to be axonally transported within the optic nerve.
This protein is termed p68/70, reflecting its relative migration in 10%
SDS-PAGE. In the present study, an affinity-purified polyclonal antibody to
p68/70 (anti-p68/70) was developed and used to assess the species, tissue,
and cellular distribution of p68/70. The antibody cross-reacted with
homogenates of brain and other tissues from goldfish and closely related
fish species. While each goldfish tissue tested expressed p68/70, the
levels varied over a 30-fold range, with the highest amounts in brain, egg,
and ovary. Immunolabeling of goldfish retina revealed prominent staining of
RGC somata, dendrites, and axons. During regeneration, the immunoreactivity
of the RGC somata and axons increased dramatically. Intense immunolabeling
was also observed in the germinal neuroepithelial cells and rod precursors
and in all retinal layers near the peripheral margin, in the region of
recently differentiated neurons. In the tectum, the germinal zone was also
highly labeled. The elevated expression of p68/70 in each of these areas
known to mediate neuronal growth within the goldfish visual system suggests
that p68/70 plays a role in axonal growth, regrowth, and possibly in neural
development as well.