Abstract
Mueller glial reprogramming studies demonstrate that mammalian Mueller glia can be induced to proliferate and/or engage in neural differentiation, as occurs naturally in teleost fish. A major objective is the identification of combined strategies that promote both robust proliferation and neurogenesis. These studies would benefit from a translatable screening platform that enables controlled perturbation, maintained tissue context and longitudinal analysis, such as 3D culture for first tier analysis of reprogramming strategies. Here, we validate a 3D retinal culture for Mueller glial reprogramming studies by recapitulating key signatures of an in vivo reprogramming paradigm. Next, we find that electrical stimulation (E-stim) as a tunable, extrinsic cue is sufficient to activate endogenous Ascl1 expression, indicating a state transition favorable for neurogenesis, while Mueller glia-specific p27 (Kip1) inactivation promotes robust, prolonged proliferation. Utilization of the lineage-tracing proliferation-history reporter H3.1-iCOUNT enabled longitudinal proliferation analysis and assessment of reprogramming outcomes within the proliferative, Mueller-derived population. With this model, we find that E-stim and p27 (Kip1) inactivation in combination (ESPI) increases proliferation, endogenous Ascl1 expression, and neurogenesis of Mueller-derived cells across modalities. Together, this work establishes a 3D culture framework for discovery of combinatorial reprogramming strategies within a proliferative context and identifies ESPI as an efficient approach to proliferative, neurogenic Mueller glial reprogramming.