Tenascin-R and axon growth-promoting molecules are up-regulated in the regenerating visual pathway of the lizard (Gallotia galloti).
It is currently unclear whether retinal ganglion cell (RGC) axon regeneration depends on down-regulation of axon growth-inhibitory proteins, and to what extent outgrowth-promoting substrates contribute to RGC axon regeneration in reptiles. We performed an immunohistochemical study of the regulation of the axon growth-inhibiting extracellular matrix molecules tenascin-R and chondroitin sulphate proteoglycan (CSPG), the axon outgrowth-promoting extracellular matrix proteins fibronectin and laminin, and the axonal tenascin-R receptor protein F3/contactin during RGC axon regeneration in the lizard, Gallotia galloti. Tenascin-R and CSPG were expressed in an extracellular matrix-, oligodendrocyte/myelin- and neuron-associated pattern and up-regulated in the regenerating optic pathway. The expression pattern of tenascin-R was not indicative of a role in channeling or restriction of re-growing RGC axons. Up-regulation of fibronectin, laminin, and F3/contactin occurred in spatiotemporal patterns corresponding to tenascin-R expression. Moreover, we analyzed the influence of substrates containing tenascin-R, fibronectin, and laminin on outgrowth of regenerating lizard RGC axons. In vitro regeneration of RGC axons was not inhibited by tenascin-R, and further improved on mixed substrates containing tenascin-R together with fibronectin or laminin. These results indicate that RGC axon regeneration in Gallotia galloti does not require down-regulation of tenascin-R or CSPG. Presence of tenascin-R is insufficient to prevent RGC axon growth, and concomitant up-regulation of axon growth-promoting molecules like fibronectin and laminin may override the effects of neurite growth inhibitors on RGC axon regeneration. Up-regulation of contactin in RGCs suggests that tenascin-R may have an instructive function during axon regeneration in the lizard optic pathway.
Lang
Dirk M
DM
Department of Human Biology, Faculty of Health Sciences, University of Cape Town, South Africa. dirk.lang@uct.ac.za
Monzon-Mayor
Maximina
M
Del Mar Romero-Aleman
Maria
M
Yanes
Carmen
C
Santos
Elena
E
Pesheva
Penka
P
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D011508:Chondroitin Sulfate Proteoglycans / Q000235:genetics / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism; D007839:Functional Laterality; D005727:Ganglia, Spinal / Q000166:cytology; D008116:Lizards / Q000033:anatomy & histology / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000637:transplantation; D020221:Optic Nerve Injuries / Q000503:physiopathology; D051381:Rats; D012160:Retina / Q000502:physiology / Q000637:transplantation; D019063:Tenascin / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation / Q000502:physiology*; D014795:Visual Pathways / Q000378:metabolism* / Q000503:physiopathology*
D011508:Chondroitin Sulfate Proteoglycans; D005136:Eye Proteins; D009419:Nerve Tissue Proteins; D019063:Tenascin; C074638:tenascin R