Does ALS-FUS without FUS mutation represent ALS-FET? Report of three cases

Abnormal cytoplasmic accumulation of fused in sarcoma (FUS) protein is the pathological hallmark of some cases of amyotrophic lateral sclerosis (ALS) with transactive response DNA‐binding protein of 43KDa (TDP‐43)‐negative pathology that lack SOD1 mutations. FUS is an RNA‐binding protein located predominantly in the nucleus and is involved in regulation of transcription, alternative splicing, RNA stability, microRNA biogenesis, apoptosis and cell division. FUS, Ewing's sarcoma (EWS) and TATA‐binding protein‐associated factor 15 (TAF15) proteins constitute the FET (FUS/EWS/TAF15) family, highly conserved and ubiquitously expressed RNA‐binding proteins that shuttle between nucleus and cytoplasm assisted by the nuclear import protein Transportin 1 (Trn1)This study was partially funded by Fundació Marató de TV3 (grant no. 20143810 to RSV, no. 20141610 to EG and no. 201437.10 to RRG) and Fondo Europeo de Desarrollo Regional (FEDER) (PI16/01673 to JG and PI15/01618 to RRG)