GSE135414
STAT pathway activation limits the Ascl1-mediated chromatin remodeling required for neural regeneration from Müller glia in adult mouse retina
Müller glia can serve as a source for retinal regeneration in some non-mammalian vertebrates. Recently we found that this process can be induced in mouse Müller glia after injury, by combining transgenic expression of the proneural transcription factor Ascl1 and the HDAC inhibitor TSA. However, new neurons are only generated from a subset of Müller glia in this model, and identifying factors that limit Ascl1-mediated MG reprogramming could potentially make this process more efficient, and potentially useful clinically. One factor that limits neurogenesis in some non-mammalian vertebrates is the STAT pathway activation that occurs in Müller glia in response to injury. In this report, we tested whether injury induced STAT activation hampers the ability of Ascl1 to reprogram Müller glia into retinal neurons. Using a STAT inhibitor, in combination with our previously described reprogramming paradigm, we found a large increase in the ability of Müller glia to generate neurons, similar to those we described previously. Single-cell RNA-seq showed that the progenitor-like cells derived from Ascl1-expressing Müller glia have a higher level of STAT signaling than those that become neurons. Using Ascl1 ChIP-seq and DNase-seq, we found that developmentally inappropriate Ascl1 binding sites (that were unique to the overexpression context) had enrichment for the STAT binding motif. This study provides evidence that STAT pathway activation reduces the efficiency of Ascl1-mediated reprogramming in Müller glia, potentially by directing Ascl1 to developmentally inappropriate targets. Overall design: Characterizing epigenetic and transcriptomic differences between Müller glia and Ascl1-mediated  reprogrammed Müller glial-derived neurons. Ascl1 ChIP-seq datasets from developmental P0 whole retina to determine where Ascl1 binds normally in development. Ascl1 ChIP-seq datasets from P12 cultured Müller glia to determine where Ascl1 binds in a transgenic overexpression model. Ascl1 ChIP-seq datasets from P12 cultured with/without a STAT pathway inhibitor to determine STAT's effect on Ascl1 binding. Single-cell RNA-seq dataset from FACS-purified MG-derived neurons that received improved reprogramming paradigm, including an intravitreal injection of a STAT pathway inhibitor.