Local translation is engaged to sustain synaptic function in impaired Wallerian degeneration

After injury, severed axons separated from their somas activate programmed axon degeneration, a conserved pathway to initiate their degeneration within a day. Conversely, severed projections deficient in programmed axon degeneration remain morphologically preserved with functional synapses for weeks to months after injury. How this synaptic function is sustained remains currently unknown. Here, we demonstrate that dNmnat-mediated over-expression attenuates programmed axon degeneration in distinct neuronal populations. Severed projections remain morphologically preserved for weeks. When evoked, they elicit a postsynaptic behavior which is a readout for preserved synaptic function. We used ribosomal pulldown to isolate translatomes from these projections. Transcriptional profiling revealed several enriched biological classes. Identified candidates were validated in a screen using a novel automated system to detect evoked antennal grooming as a proxy for preserved synaptic function. We used RNAi-mediated knockdown to identify mTOR as a mediator of protein synthesis, and candidates involved in protein ubiquitination and calcium homeostasis, required for preserved synaptic function. Our dataset uncovered several uncharacterized genes linked to human diseases. It may offer insights into novel avenues for therapeutic treatments. Ribosomal pulldowns were performed using GFP::Rpl10Ab, in three genotypes (background, wild type and over-expression of dNmnat, respectively) with two conditions (e.g., before and 7 days after injury).