TDP-43 mis-localization alters synaptic mitochondria local protein synthesis and facilitates NMJ disruption in ALS

Amyotrophic Lateral Sclerosis (ALS) is a devastating, rapidly progressing neurodegenerative disease that specifically affects motor neurons (MN). TDP-43 cytoplasmic localization and mitochondrial defects are both key contributors to ALS pathology. However, little is known about the mechanism underlying MN vulnerability regarding this combination of cellular stress. Here, we hypothesize that cytoplasmic presence of TDP-43 affect the protein synthesis of nuclear encoded mitochondrial proteins, specifically at mitochondria enriched synapse such as the neuromuscular junction (NMJ). To mimic disease pathology, we use inducible mice model of TDP-43 that lacks nuclear localization signal (NLS) and shows fast progressing MN disease, with both in vivo and in vitro phenotypes. We demonstrate negative effects of cytoplasmic TDP-43 on cell viability and NMJ activity using various approaches including a unique microfluidic platform to model the motor unit. Furthermore, we examine the spatial effects of cytoplasmic TDP-43 on mitochondrial protein translation and mRNA transport using MS2 constructs and proximity ligation assays. There are currently no efficient therapies for ALS patients, and we believe this project can improve our understanding of the disease and provide novel therapeutic avenues in the future.