A Mutation in the Borcs7 Subunit of the Lysosome Regulatory BORC Complex Results in Motor Deficits and Dystrophic Axonopathy in Mice

Lysosomes play a critical role in maintenance of the integrity of neuronal function, and mutations in genes that contribute to lysosome formation, transport, and activity are associated with neurodegenerative disorders. Recently, the multisubunit complex, BLOC-one-related complex (BORC), has been shown to be involved in positioning lysosomes within the cytoplasm, although the consequences of altered BORC function in adult animals have not been established. We show that a spontaneous truncation mutation in the mouse Borcs7 gene, identified through whole-genome sequencing followed by genetic complementation, results in progressive axonal dystrophy with dramatic impairment of motor function. Furthermore, mice homozygous for deletion of the entire Borcs7 coding sequence die shortly after birth, and neurons cultured from these animals show impaired centrifugal transport of lysosomes. This identifies BORCS7 as a central factor in axonal transport of lysosomes and a possible target for improving disease-related disturbances in this important function.