Journal of Neuroscience, Vol 10, 641-648, Copyright © 1990 by Society for Neuroscience
Slow transport rates of cytoskeletal proteins change during regeneration of axotomized retinal neurons in adult rats
L McKerracher, M Vidal-Sanz and AJ Aguayo
Center for Research in Neuroscience, Montreal General Hospital, Quebec, Canada.
To investigate cytoskeletal changes associated with axonal regrowth from
damaged nerve cells in the mammalian CNS, we examined the slow transport of
axonal proteins during the regeneration of adult rat retinal ganglion cell
(RGC) axons. Although normally such RGC axons do not regrow after injury in
the CNS, they can extend several centimeters when their nonneuronal
environment is changed by replacing the optic nerve (ON) with a grafted
segment of peripheral nerve (PN). Proteins transported in axons of RGCs
from intact control and PN-grafted animals were labeled by an intraocular
injection of 35S-methionine and examined 4-60 days later by SDS PAGE.
During RGC regeneration into PN grafts, the transport rate of tubulin and
neurofilament increased twofold, whereas that of actin decreased to nearly
one third of its normal rate. Thus, in these regenerating RGC axons, all
three major cytoskeletal proteins were largely transported within a single
rate component rather than in the two separate components (SCa and SCb)
normally observed in the intact ON. Furthermore, the 200 kDa neurofilament
protein (NF-H) was persistently detected in Western blots during periods of
active regeneration, a finding that contrasts with the late appearance of
the NF-H during the developmental growth of retinal axons. The changes in
slow transport observed during RGC regeneration in adult rats may reflect
growth-associated responses of mature CNS neurons during periods of active
axonal extension.