Microtubule decay is a driver of neuronal ageing and a promising target for intervention

Natural ageing is accompanied by a decline in motor, sensory and cognitive functions, all impacting life quality. Ageing is the predominant risk factor for many neurodegenerative diseases, including Parkinsons and Alzheimers disease. We need therefore to gain a better understanding of the cellular and physiological processes underlying age-related neuronal decay. However, gaining this understanding is a slow process due to the long time required to age mammalian or vertebrate model animals. Here we introduce a new cellular model within the Drosophila brain where neurons show typical ageing hallmarks known from the primate brain, including axonal swellings, cytoskeletal decay, a reduction in axonal calibre and morphological changes arising at synaptic terminals. In the fly brain, these changes occur within just a few weeks, ideal to study the underlying mechanisms. We observe that decay of the neuronal microtubule cytoskeleton clearly precedes other ageing hallmarks. We show that the microtubule-binding factors Tau, EB1 and Shot, are necessary for microtubule maintenance in axons and synapses. Their functional loss during ageing triggers microtubule bundle decay followed by the decline in axons and synapses. Genetic manipulations that improve microtubule networks, slow down other neuronal ageing hallmarks and confer aged specimens with the ability to outperform age-matched controls. Our work suggests therefore that microtubule networks are a key lesion site in ageing neurons and offer promising opportunities to improve neuronal decay in advanced age.