Modeling Human Retinal Ganglion Cell Development and Connectivity

In humans, retinal ganglion cell (RGC) loss, as occurs in glaucoma, is irreversible and this leads to permanent loss of vision. Endogenous regeneration, the process whereby new neurons are created from existing glial cells, offers one possible approach to address this condition. For this approach to succeed there is still much that needs to be learned about RGC during development. To address this, carried out three lines of research including (1) human pluripotent stem cell derived retina/brain co-culture experiments to evaluate axon targeting, (2) WNT agonist treatments to improve retinal organoid differentiation, and (3) direct conversion of RGCs from pluripotent stem cells in order to explore how axons project from the eye to the brain. For co-culture experiments retinal organoids were complexed with thalamus and cortical organoids. RGCs showed axon neurite outgrowth when cultured in conditions used to induce thalamus and cortical organoids. For experiments designed to improve differentiation, different concentrations of the WNT agonist CHIR99021 was tested on developing retinal organoids at different time points. Treatments from days 16 to day 22 showed generally improved retinal vesicle quality. Based on ongoing work in the lab aimed at exploring direct conversion to probe transcription factors important for RGC development, NEUROG2, ATOH7, ISL1, and POU4F2 were shown to differentiate iPSCs into RGCs. Using this approach, I developed inducible neurons with and without retinal ganglion cell qualities. Overall, these new tools and concepts will provide new insight into human retinal ganglion cell development