Human Retinal Ganglion Cells Respond to Evolutionarily Conserved Chemotropic Cues for Intra Retinal Guidance and Regeneration.

Retinal ganglion cells (RGCs) connect the retina with the higher centers in the brain for visual perception. Their degeneration leads to irreversible vision loss in patients with glaucoma. The mechanism underlying human RGCs (hRGCs) axon growth and guidance remains poorly understood because hRGCs are born during development and connections with the central targets are established before birth. Here, using RGCs directly generated from human embryonic stem cells, we demonstrate that hRGCs express a battery of guidance receptors. These receptors allow hRGCs to read the spatially arrayed chemotropic cues in the developing rat retina for the centripetal orientation of axons toward the optic disc, suggesting that the mechanism of intraretinal guidance is conserved in hRGCs. The centripetal orientation of hRGCs axons is not only in response to chemorepulsion but also involves chemoattraction, mediated by Netrin-1/DCC interaction. The spatially arrayed chemotropic cues differentially influence hRGCs physiological responses, suggesting that neural activity of hRGCs and axon growth may be coupled during inter-retinal guidance. In addition, we demonstrate that Netrin-1/DCC interaction, besides promoting axon growth, facilitates hRGCs axon regeneration by recruiting the mTOR signaling pathway. The diverse influence of Netrin-1/DCC interaction ranging from axon growth to regeneration may involve recruitment of multiple intracellular signaling pathways as revealed by transcriptome analysis of hRGCs. From the perspective of ex vivo stem cell approach to glaucomatous degeneration, our findings posit that ex vivo generated hRGCs can read the intraretinal cues for guidance toward the optic disc, the first step required for connecting with the central target to restore vision.