PRPH and amyotrophic lateral sclerosis: Among these, the importance of cytoskeletal impairment and disrupted axonal transport is directly suggested by the function of proteins encoded by several genes responsible for familial ALS, including neurofilament heavy chain (4), dynactin subunit 1 (5), peripherin (6), profilin 1 (7), tubulin alpha 4a (8), and kinesin family member 5A (9).