Examples include KO of Msh2 (encoding DNA damage repair protein MSH2) or Prkaa1 (encoding AMP-activated protein kinase AMPKα1) resulting in merely pro-B or pre-B lymphomas [45,51] or, on the contrary, KO of Ube3a (encoding Ubiquitin-Protein-Ligase E3A), which shifts the phenotype towards mature B-cell lymphomas [52]. The gene discussed is MSH2; the disease is lymphoma.