ASPSCR1 and soft tissue sarcoma: Human UBXD9, also known as ASPL (alveolar soft part sarcoma locus) or TUG (tether containing a UBX domain for GLUT4), was originally identified in a genetic screen as part of an oncogenic fusion protein with the transcription factor TFE3 in alveolar soft part sarcoma cells (Ladanyi et al., 2001).