PAX3 and myopathy: Interestingly, the induction of SYT-SSX expression through Hprt-Cre, Pax3-Cre, or Pax7-Cre resulted in embryonic lethality, and SYT-SSX expression in Myf6-expressing myocytes or Myf6-expressing myofibers resulted in myopathy but no tumors.