Mimicking of tau hyperphosphorylation in GABAergic motoneurons of C. elegans induces severe peripheral and neuronal alterations

In several neurodegenerative diseases including Alzheimers disease (AD), tau, a microtubule-associated protein (MAP) enriched in the axon, becomes hyperphosphorylated, detaches from microtubules, redistributes to the somato-dendritic compartment and self-aggregates. The mechanisms leading to neuronal dysfunction and death by tau pathology remain to be fully elucidated. C. elegans has been successfully used by several groups including ours to identify mechanisms involved in neurodegeneration. We generated three strains, one overexpressing wild-type human tau (WT Tau), one a tau mutant mimicking hyperphosphorylation (hyperP Tau) and one preventing phosphorylation (hypoP Tau) in GABA motor neurons. A significant reduction of body size and egg laying was noted in these tau strains. Starting at day 1, we found that the worms overexpressing hyperP Tau were smaller than the N2 control strain and the worms either overexpressing WT Tau or hypoP Tau. Starting at day 5, the worms overexpressing WT Tau were smaller than control and the worms overexpressing hypoP Tau. Egg laying was reduced in both hyperP Tau and WT Tau worms. Survival was only decreased in WT Tau worms. Motility deficits were also observed. For age-dependent paralysis, a difference was noted between control and hyperP Tau. Swimming activity and speed were increased in hypoP Tau and decreased in hyperP Tau strains. Axonal integrity was altered in all tau strains. In the case of synaptic activity, at day 1, it was increased in the hypoP Tau strain and decreased in the hyperP Tau one. Collectively, our data revealed that overexpression of tau exerted neuronal and peripheral defects indicating that tau dysfunction could affect cell-cell communication.