Autophagy induction mitigates FUS aggregate formation and early synaptic dysfunction at the NMJ in the FUS-ALS model

Abstract

Mutations in Fused in Sarcoma (FUS), a RNA binding protein, cause Amyotrophic Lateral Sclerosis (ALS). ALS is an aggressive neurodegenerative disease resulting in motor neuron degeneration. Defects in synaptic integrity precede neuronal loss in ALS, but the mechanisms responsible for these early synaptic defects are unclear. To investigate early synaptic defects associated with ALS, we expressed an ALS-linked variant of human FUS in adult motor neurons and assessed synaptic pathology at the neuromuscular junction (NMJ). Here we highlight the accumulation of FUS-positive aggregates at synaptic terminals and subsequent reduction in microtubule stability. We show that inducing autophagy via expression of Rab1 or Fragile-X Mental Retardation Protein 1 (FMR1), or treatment with Rapamycin reduces aggregate formation and restores synaptic structure and function. These findings reveal the utility of inducing autophagy to address early synaptic dysfunction in an ALS model and demonstrate a potential therapeutic target to preventing later stages of disease progression.