Journal of Neuroscience, Vol 16, 2624-2634, Copyright © 1996 by Society for Neuroscience
mCD24, a glycoprotein transiently expressed by neurons, is an inhibitor of neurite outgrowth
D Shewan, V Calaora, P Nielsen, J Cohen, G Rougon and H Moreau
Department of Developmental Neurobiology, United Medical and Dental Schools, Guy's Campus, London, United Kingdom.
In the immune system, mCD24, the mouse homolog of the human glycosyl
phosphatidylinositol-anchored glycoprotein CD24, may play a role in cell
adhesion. In the nervous system, the function of mCD24 has not been
determined, but its transient expression by neurons suggests that it may be
involved in axon growth in development. Here we show that retinal ganglion
cells (RGCs) and dorsal root ganglion (DRG) neurons express mCD24 in the
developing but not adult mouse in vivo and in DRG neurons of the injured
adult peripheral nervous system (PNS). In vitro, mCD24 was expressed by
immature neurons and by a subpopulation of adult DRG neurons. To analyze
the possible function of mCD24 in the nervous system, we prepared rat C6
glioma cells stably transfected or retrovirally infected with mCD24 cDNA.
The cells did not exhibit changes in their adhesive properties or cell
division rate after transfection or infection. When mCD24-expressing cells
were used as monolayer substrates for culturing RGCs and DRG neurons,
neurite outgrowth was inhibited, depending on neuronal age and on the
relative levels of mCD24 in the monolayer. This inhibition, however, was
not dependent on the expression of mCD24 by the neurons themselves, because
DRG neurons of a mouse deleted of the mCD24 gene showed the same response.
These results show that mCD24 interacts in a heterophilic manner with a
developmentally regulated molecule expressed by neurons, and they suggest
that in vivo, mCD24 may inhibit the further extension or collateral
branching of axons in late embryonic development.
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