However, the axonal spheroids in AP-4 ε KO mice appear similar to those observed in other human or mouse models of HSP, including SPG2 [33], SPG4 [34], SPG7 [35], SPG10 [36], SPG11 [37], SPG35 [38] and SPG79 [39]. This evidence concerns the gene FA2H and hereditary spastic paraplegia.