Abstract
Purpose:
Teleost fish have a robust ability to regenerate retinal neurons from Müller glia cells. In contrast, mammalian Müller glia have a limited regenerative response. Previous studies have shown that the proneural transcription factor, Ascl1, is expressed in fish Müller glia early in the regeneration process; however, this factor is not reactivated in mouse Müller glia after injury. Therefore, we tested whether viral overexpression of Ascl1 could restore a neurogenic potential to mouse Müller glia.
Methods:
Müller glia were grown as dissociated cultures or in retinal explants and infected with lentiviruses encoding Ascl1 or GFP. Cultures and explants were examined for progenitor and retinal neuronal gene expression by RT-PCR, microarray analysis, and single cell immunohistochemistry. Functional analysis of cells was carried out using ratiometric calcium imaging.
Results:
Müller glia expressing Ascl1 upregulated retinal progenitor-specific genes, while downregulating glial genes by microarray analysis and RT-PCR. Müller glia-derived progenitors further differentiated into cells that exhibited neuronal morphologies and expressed pan-neuronal and retinal subtype-specific neuronal markers, including Otx2, Islet1, Calretinin, and PKC. Müller glial-derived neurons responded to glutamate agonists with increases in calcium signaling and decreased responsiveness to purinergic agonists.
Conclusions:
These results indicate that a progenitor program can be reactivated in mammalian Müller glia through the re-expression of the proneural transcription factor Ascl1. These progenitors differentiate into functional retinal neurons both in dissociated cultures and in the intact retina, suggesting that Müller glia may be a useful source of endogenous replacement of mammalian retinal neurons in the future.
Keywords: 688 retina •
603 Muller cells •
687 regeneration