Figure 10.

Our data indicate that there is a yet unknown ligand located on or associated with glial endfeet of retinal Müller glia cells. Signaling into the growth cone is mediated via the CRYPα1 receptor. These signals are important for outgrowth and the actin cytoskeleton. According to the work from other groups, it is likely that downstream signaling is mediated via the Trio protein, which is capable of activating rac and rho. The integrin receptor mediates the laminin signal from the ECM into the growth cone. It has been previously shown that integrin downstream activates Rac and Cdc42. So both receptors mediate signals, that are important for axon outgrowth and growth cone morphology. The CRYPα1-ligand interaction is growth-promoting and could balance a negative interaction between the growth cone and Müller glia cells. The glial endfeet, therefore, appear to have a strict growth controlling function containing a balance of growth promoting and inhibiting factors on their surfaces.