Journal of Neuroscience, Vol 9, 2645-2653, Copyright © 1989 by Society for Neuroscience
Changes in cytoskeletal gene expression affect the composition of regenerating axonal sprouts elaborated by dorsal root ganglion neurons in vivo
MM Oblinger, RA Szumlas, J Wong and FJ Liuzzi
Department of Cell Biology and Anatomy, Chicago Medical School, Illinois 60064.
The effect of a change in neurofilament (NF) and tubulin gene expression on
the elongation of axonal sprouts by adult rat sensory neurons was examined.
Distal sciatic nerve crush axotomy was used to initiate changes in
cytoskeletal gene expression in lumbar dorsal root ganglion (DRG) neurons.
In situ hybridization of DRG neurons with 35S- labeled cDNA probes revealed
a significant reduction in the level of mRNAs for the low-molecular
weight-NF protein and a significant increase in the level of beta tubulin
mRNAs by 2 weeks after axotomy. A novel modification of the axonal
transport paradigm was used to examine the biochemical composition of the
regenerating axons formed by primed and unprimed DRG neurons. Primed
neurons (which had sustained a crush axotomy of the distal sciatic nerve 2
weeks earlier) and unprimed (normal) neurons were labeled by microinjection
of 35S-methionine and then stimulated to regenerate axons by a crush
located very close to the DRG. In this paradigm, axonal sprouts that formed
after the proximal crush axotomy incorporated radiolabeled, slow axonally
transported proteins as they elongated. Fluorographs of SDS-PAGE revealed
that the regenerating axonal sprouts of primed DRG cells incorporated and
conveyed significantly less labeled NF protein than did the regenerating
axons of unprimed DRG neurons. Electron microscopy revealed that the
regenerating axonal sprouts of primed DRG cells contained numerous
microtubules but very few identifiable NFs compared with the regenerating
sprouts of unprimed DRG neurons.(ABSTRACT TRUNCATED AT 400 WORDS)