RTN4 and stroke disorder: Molecules in the adult CNS milieu, such as myelin-associated proteins (e.g., Nogo, MAG, and Omgp), factors secreted by astrocytes near the stroke site (e.g., chondroitin sulfate proteoglycans), and repulsive axonal guidance cues (e.g., semaphorins, netrins, and members of the ephrin family), constrain axonal sprouting and hamper the formation of new connections [6].