Model Description: A IRES-iCre expression cassette was knocked into the Pax7 gene stop codon site. Pax7 is expressed in myogenic progenitor cells. Pax7 is essential for the myogenic potential, survival, and proliferation of myogenic progenitors. When crossed with a strain carrying a gene flanked by loxP sites, the flanked gene will be removed in cells expressing Pax7.