Februaray – August 2022
Children’s Hospital of Philadelphia
Supported by the Austrian Marshall Plan Foundation
Abstract
Neuroregeneration is of both clinical and socioeconomic concern; especially given the disparities in the regenerative potential of the central nervous system (CNS) and peripheral nervous system (PNS). Many intrinsic and extrinsic factors of regeneration have been identified. In this work we explored the role of glia in neuroregeneration. Previous work of the Song Lab indicated that glia send pro- and anti-generative signals to neurons after axotomy. The hypothesized pathways include the sole Drosophila tumor necrosis factor (TNF) Eiger as well as adenosine signals. We used a larval Drosophila sensory neuron laser axotomy model to test over 15 different genotypes for their impact on regeneration. We also aimed to reproduce a human organoid model and build upon it to establish a novel nerve injury model in the future. This work suggests that the recently discovered fly tumor necrosis factor receptor (TNFR) Grindelwald is not involved in sensory neuron regeneration, in contrast to the other TNFR Wengen. We also tested several genes that might relay a proregenerative TNF signal downstream of Wengen to L-type voltage-gated calcium channels (VGCCs). We investigated the interplay of these potential downstream signal transducers and found indications of a compensatory intermediate mechanism, be it other signaling proteins or transcriptional regulation. We also explored an anti-regenerative adenosine pathway, that we suspect to converge on the same VGCC. A global loss-of-function mutation, but not glia-specific RNA interference (RNAi) knock-down (KD), of the adenosine transporter MFS18 increased regeneration 2-fold. In addition, we replicated important aspects of an organoid model, that contains neurons, glia and muscle. We subsequently improved it by generating transgenic organoids to enable live-imaging of motor neurons without immunofluorescence staining. In summary, in a short time we performed a candidate-based screen of 15 alleles, to explore two potential converging pathways that allow glia to modulate neuronal electrochemical properties and thus regeneration. We also, for the first time in the Song Lab, established a neural organoid model and paved the way for the first human organoid nerve injury paradigm.
