In these mice, rhabdomyosarcoma is only induced when a Pax3:Foxo1 fusion oncogene is activated with concurrent loss of p53 function (for alveolar rhabdomyosarcoma) or loss of p53 function alone (for embryonal rhabdomyosarcoma) using Cre-lox technology. The gene discussed is FOXO1; the disease is rhabdomyosarcoma.