The Journal of Neuroscience, February 1, 2002, 22(3):842-853
Repellent Guidance of Regenerating Optic Axons by Chondroitin
Sulfate Glycosaminoglycans in Zebrafish
Catherina G.
Becker and
Thomas
Becker
Zentrum für Molekulare Neurobiologie Hamburg,
Universität Hamburg, D-20246 Hamburg, Germany
We analyzed the role of chondroitin sulfate (CS)
glycosaminoglycans, putative inhibitors of axonal regeneration in
mammals, in the regenerating visual pathway of adult zebrafish. In the adult, CS immunoreactivity was not detectable before or after an optic
nerve crush in the optic nerve and tract but was constitutively present
in developing and adult nonretinorecipient pretectal brain nuclei,
where CSs may form a boundary preventing regenerating optic fibers from
growing into these inappropriate locations. Enzymatic removal of CSs by
chondroitinase ABC after optic nerve crush significantly increased the
number of animals showing erroneous growth of optic axons into the
nonretinorecipient magnocellular superficial/posterior pretectal
nucleus (83% vs 42% in controls). In vitro, a
substrate border of CSs, but not heparan sulfates, strongly repelled
regenerating retinal axons from adult zebrafish. We conclude that CSs
contribute to repellent axon guidance during regeneration of the optic
projection in zebrafish.
Key words:
CNS regeneration; extracellular matrix; chondroitin
sulfate proteoglycans; heparan sulfate; chondroitinase ABC; tenascin-R; retinal ganglion cell axons; neurite outgrowth
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