Figure 2. Conditional expression of Cas9 to generate tumours in a primary mouse model of sarcoma.

(a) Kras^LSL-G12D/+ (K), Rosa26^{LSL-Cas9-EGFP/+} (C), or Kras^LSL-G12D/+; Rosa26^{LSL-Cas9-EGFP/+} (KC) mice received intramuscular injections of an adenovirus carrying the plasmid. (b) Adenoviral delivery of sgTrp3-Cre resulted in efficient primary sarcoma formation by activating conditional expression of the mutant Kras and Cas9 alleles and delivering a sgRNA to target Trp53. (c) PCR analysis and Surveyor assay showing recombination of Kras^LSL-G12D and Rosa26^{LSL-Cas9-EGFP}, as well as indels within the Trp53 gene, respectively. (d) Twelve of the primary tumours generated via adenoviral plasmid delivery were subject to histopathological analysis with staining for myogenic markers MyoD and myogenin. (e) The majority of tumours resembled UPS, whereas a minority were consistent with a myogenic UPS phenotype. Scale bars, 500 μm.