C9orf72 and amyotrophic lateral sclerosis: In conclusion, our results demonstrate that surface glia, particularly PNG and SPG, are highly susceptible to the toxic effects of mutant C9orf72, leading to significant developmental toxicity, impaired locomotor function, and reduced lifespan in Drosophila. The distinct response to UDCA treatment in glial versus neuronal models underscores the complexity of ALS-FTD pathogenesis and highlights the importance of considering non-neuronal cell types in disease research and therapeutic development.