Recent data suggest a continuum in motoneuron disorders; several genes can underlie different phenotypes, resembling ALS, HSP and HM(SA)N respectively (reviewed in [19]), e.g. Alsin (ALS2) [20-22], Senataxin (ALS4) [23,24], NIPA1 (SPG6, NIPA1 repeat expansions associated with ALS) [25,26], BSCL2 (SPG17, HMSN V) [27-29], Atlastin-1 (SPG3, HSN-I) [30-32], KIF1A (SPG 30, HSAN-II) [33,34], and REEP1 (SPG31, dHMN-V) [35,36]. Here, REEP1 is linked to amyotrophic lateral sclerosis.