SACS and Autosomal recessive spastic ataxia of Charlevoix-Saguenay: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS, OMIM 270550) is a rare inherited neurodegenerative disease caused by mutations in SACS [1], which encodes sacsin (also called DnaJ homolog subfamily C member 29, DNAJC29), a 520 kDa multi-domain chaperone [2,3] mainly involved in mitochondrial dynamics [4,5], autophagy [6], cytoskeletal intermediate filament assembly and dynamics [7,8], and axonal growth [9].