Remodeling of chromatin and transcriptomic landscape to enhance optic nerve regeneration

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Summary Long distance axon regeneration is one of the most important aspects and a prerequisite for successful functional recovery after optic nerve injuries. Although great progress has been made to enhance the intrinsic axon regeneration ability via various approaches, long distance optic nerve regeneration reaching the original targets in the brain remains a major challenge. We think that extending sufficient number of injured RGC axons from different RGC subtypes into the brain should be the major tasks for functional recovery after visual injuries. Therefore, a new strategy is needed to 1) enhance RGC survival rate, 2) identify additional gene targets capable of enhance regeneration from a diverse subtypes of RGCs, and 3) promote extensive long-distance optic nerve regeneration that is less affected by the inhibitory environment. During RGC maturation, their chromatin structures change temporally, leading to changed transcriptomics underlying the loss of intrinsic ability to support axon regeneration. Conversely, the current identified genes that act to enhance optic nerve regeneration presumably alter the developmental changes in transcriptomics in some way. Thus, it is important to reveal the chromatin and transcriptomics landscape of RGCs favorable for axon regeneration, and identify key transcription factors and/or chromatin modulators underlying such chromatin state of regenerating RGCs. In Aim 1, by performing RNA-seq, ATAC-seq and ChIP-seq of purified RGCs at different maturation stages, and different regenerative states, we will use advanced integrative bioinformatics analyses to reveal the chromatin and transcriptomics landscape of RGCs favorable for axon regeneration, and identify key transcription factors and/or chromatin modulators underlying such chromatin state of regenerating RGCs. In Aim 2, we will perform functional screening experiments to determine their roles in regulation of RGC survival and/or optic nerve regeneration, and their underlying mechanisms. Our recent work showed that deleting non-muscle myosin IIA/B or histone demethylase UTX, when combined with enhanced intrinsic axon regeneration ability, could lead to extensive long-distance optic nerve regeneration. Based on these results, in Aim 3, we will explore if combining the newly identified transcription factors with UTX and myosin IIA/B knockout could induce long distance optic nerve regeneration into the brain. The proposed studies will not only generate a detailed picture of changes in transcriptomics, chromatin accessibility and epigenetic landscape of RGCs during maturation and regeneration, but also identify novel molecular targets and optimized approaches to re-establish visual circuity.