IMMUNOHISTOLOGICAL LOCALIZATION OF TENASCIN-C IN THE DEVELOPING AND REGENERATING RETINOTECTAL SYSTEM OF 2 AMPHIBIAN SPECIES

The expression pattern of the extracellular matrix molecule tenascin-C was investigated in the retinotectal system of the frog Discoglossus pictus and the salamander Pleurodeles waltl during development and opt ic nerve regeneration in the adult. In both species, the retina was de void of tenascin-C immunoreactivity at all ages studied. During develo pment, tenascin-C was distributed in a gradient in the optic nerve, wi th the highest immunoreactivity in the eye near part of the optic nerv e. The myelin-associated glycoprotein was distributed in a gradient wi th opposite polarity. In Discoglossus, but not Pleurodeles, tenascin-C was detected in the anterior chiasm. In the tectum of both species, t enascin-C was observed in deep cellular and fiber layers but not in th e layers receiving optic fibers or proliferative zones. The distributi on patterns of tenascin-Ct were the same during development and in the adult, except for a disappearance of the molecule from the intraocula r part of the optic nerve. After lesioning the optic nerve of adult an imals, tenascin-C was strongly reexpressed in the intraocular part of the optic nerve but was only weakly upregulated in the distal optic ne rve stump. In contrast, a chondroitin sulfate epitope was strongly upr egulated in the distal optic nerve stump. These observations suggest t hat during development, tenascin-C serves as an attenuating barrier fo r myelinating cells in the optic nerve and contributes to the guidance of growing retinal ganglion cell axons. Due to its sustained expressi on in the adult, tenascin-C may have similar functions during regenera tion of the lesioned adult retinotectal system. (C) 1995 Wiley-Liss, I nc.