Investigation for molecular mechanisms by which the retinal ganglion cells perceive carbohydrate chains of chondroitin sulfate proteaglycans (chondroitin sulfate) as axonal guidance cues

Axons of retinal ganglion cells do not invade the telencephalon anteriorly. Our previous researches have shown that the telencephalic cells secrete chondroitin sulfate proteoglycans (CSPGs), and that their carbohydrate chains (chondroitin sulfates, CSs) prevent the retinal axons from invading the telencephalic territory in chick embryos.CSs exhibit their structural diversity ; the D unit rich CSs was distributed in the diencephalotelencephalic boundary. In vitro, spot of the D unit CS on the cultural substrate prevented the retina axons from invading ; however, soluble D unit CS in the culture medium has no effect on the axon outgrowth but inhibit the effect of D unit spot.To know roles of D unit CS in formation of the retinal trajectory in vivo, solution of the D unit CS was injected into lateral ventricle of the embryos ; anterior border of the optic tract shifted toward the telencephalon and the retinal axons entered the telencephalic territory aberrantly.The results indicate that structural diversity of the CSs serves their functional specificity in axon wiring. The retinal axons distinguish the D unit CS from other types of CSs, suggesting mechanisms perceiving the CSs' diversity.