Journal of Neuroscience, Vol 7, 3362-3369, Copyright © 1987 by Society for Neuroscience
Axonal signals regulate the differentiation of non-myelin-forming Schwann cells: an immunohistochemical study of galactocerebroside in transected and regenerating nerves
KR Jessen, R Mirsky and L Morgan
Department of Anatomy and Embryology, University College London, UK.
Little is known about the factors involved in directing and maintaining the
divergent differentiation of the 2 major Schwann cell variants, myelin and
non-myelin-forming cells, in peripheral nerves. There is strong evidence
that the differentiation of myelin-forming cells depends critically on
cell-cell signaling through contact with appropriate axons. In this paper
we ask whether this remarkable dependence of the Schwann cell on axonal
contact for full differentiation is unique to those cells that form myelin
or whether axonal signaling is also an important factor in the
differentiation of non-myelin-forming Schwann cells. Sciatic nerves or
cervical sympathetic trunks of adult rats were either transected or crushed
and the axons allowed to degenerate and, in the case of crushed nerves, to
regenerate into the distal stump for periods of time varying from 2 d to 9
weeks. The distal stump of the nerve was excised at specific times, the
Schwann cells dissociated and immunolabeled with antibodies to
galactocerebroside. In the sciatic nerve, which contains a mixture of
non-myelin-forming and myelin-forming Schwann cells, transection resulted
in a loss of galactocerebroside expression from the surface of all the
Schwann cells in the distal stump over a 9 week period, irrespective of
their original phenotype. In crushed sciatic nerves, where axons were
allowed to regrow into the distal stumps, the number of Schwann cells
expressing immunohistochemically detectable quantities of
galactocerebroside in the stump declined over the first 3 weeks, but by 9
weeks after crush the total percentage of galactocerebroside- positive
cells in the nerve had risen to control levels.(ABSTRACT TRUNCATED AT 250
WORDS)
