The Role of ALS8-linked VAMP-associated Protein B (VAPB) in Caenorhabditis elegans Motor Neurons

Abstract

Amyotrophic Lateral Sclerosis (ALS) is a fatal, late-onset, progressive neurodegenerative disease. A familial form of ALS, autosomal dominant ALS8, is characterized by a mutation in an ER membrane protein, VAPB. To characterize the role of VAPB in motor neurons, two C. elegans models were generated: one expressing human VAPB-P56S and another with the knockdown of C. elegans VAPB ortholog, VPR-1. Overexpression of human VAPB in DA neurons caused backward locomotion defects, enhanced vulnerability to oxidative stress and premature neuronal death. Knockdown of vpr-1 in C. elegans recapitulated the loss of protein function believed to be associated with human cases of ALS8. It caused backward locomotion defects, such as uncoordination and slowed rates of movement, as well as age-dependent motor neuronal death. In both models, DA6 and DA7 were the most vulnerable motor neurons. Because of the unexpected developmental defects associated with the VAPB transgenic model, the knockdown of vpr-1 may be a better model to recapitulate the human disease. This model provides further support that ALS8 pathogenesis is due to a loss of VAPB protein function and can also be used to test drugs or treatments that may delay the onset of neuronal death.