Reprogramming murine Müller glia for the regeneration of retinal ganglion cells

Abstract

Degenerative diseases of the retina often result in the loss of specific types of neurons. Some vertebrates, such as frogs and fish, exhibit an intrinsic regenerative capacity that can replenish lost neurons and functionally restore vision. However, the mammalian retina cannot regenerate and any vision loss from degenerative disease is permanent. Recently, it has been shown that overexpression of the proneural bHLH transcription factor Ascl1 in Müller glia (MG) can stimulate the regeneration of neurons in adult mice. While promising, regeneration is limited to one cell type – bipolar cells. Common degenerative diseases of the retina often result in the loss of other retinal neurons, such as retinal ganglion cells (RGCs) in glaucoma and diabetic retinopathy. This highlights the need to develop strategies for redirecting the fate of regenerated neurons. In this dissertation, I describe a method for inducing RGC-like neurons through the combined overexpression of Ascl1 with Pou4f2 and Isl1. I also identified three other transcription factors, Atoh1, Neurod2, and Irx2 that can improve RGC regeneration by reducing glial gene expression, improving conversion efficiency, increasing activation of axon outgrowth genes, and enhancing both the size and complexity of neurites in vitro. Overall, these studies show it is possible to induce the regeneration of clinically important neurons in the mammalian retina and suggest new strategies to further refine the approach.