ATP1A1 and synovial sarcoma: In the remaining six SS cases, we identified seven potentially dominant de novo mutations or inherited alleles as private heterozygous, mostly missense, variants of uncertain significance involving seven different NMD candidate genes: MPEG1, LHX8, WHAMM, NGRN, TTN, ATP1A1, PCDH1. All eight candidate causal variants identified were predicted to be deleterious.