Like other areas of the nervous system, the retina is subject to many acquired and inherited neuronal degenerative diseases. Since the retina provides the input for all visual sensory information to the brain, the loss of cells results in viual impairment and potentially complete blindness. Many retinal degenerative diseases affect only a subset of the retinal cells, although, frequently in more advanced disease, loss and reorganization of the entire retina can occur. In mammals, there is very limited regeneration of the degenerated cells; however, in fish, new neurons of all types regenerate from Mller glia following retinal damage and they are functionally integrated into the existing circuitry. Nevertheless, Mller glia, the cellular source for regeneration, is present in all vertebrate retins. In the proposal we submitted three years ago, we hypothesized that regeneration from mammalian Mller glia was limited because they fail to express a key proneural transcription factor, Ascl1, after injury. We proposed to test this hypothesis by virally-mediated expression of Ascl1 in mouse Mller glia. In the two years of funding, we have tested the hypothesis, and found that viral expression of Ascl1 is sufficient to activate a neurogenic program in mouse Mller glia, both in dissociated cultures and in the intact retina. The reprogrammed Mller glia generates cells that resemble neurons in morphology, gene expression and their responses to neurotransmitters. In the next funding period, we propose to further optimize this reprogramming process, using other transcription factors and epigenetic modifiers, and then to test whether Ascl1-reprogrammed Muller glia can provide a source for regeneration in vivo in a newly developed line of transgenic mice.
Like other areas of the nervous system, the retina is subject to many acquired and inherited neuronal degenerative diseases. Since regeneration of new retinal neurons does not occur in people, these diseases can leave them with permanent visual impairment. In this proposal we outline experiments to promote the regenerative potential of mammalian M?ller glia, which may lead to development of novel strategies for treatment of human retinal degeneration.
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