Activation of transposon mutagenesis in Etv6^+/RUNX1 mice. (A) Western blot showing expression of the SB transposase in the bone marrow of Etv6^+/RUNX1 (ER) mice but not mice carrying the T2Onc transposon (Onc). (B) “Excision” PCR showing mobilization of the transposon in bone marrow from Etv6^+/RUNX1; T2Onc^+/Tg (EROnc) mice, as evidenced by the 200-bp “excision” band (instead of the 2-kb band seen in mice carrying the unmobilized transposon array, ie, Etv6^+/+; T2Onc^+/Tg [Onc] mice). (C) Kaplan-Meier curves showing the tumor latency of “jumping” Etv6^+/RUNX1; T2Onc^+/Tg (EROnc) mice and “non-jumping” control mice (ER, Onc, and wild-type). (D) Categorization of the malignancies developed by mice shown in the Kaplan-Meier curve according to the Bethesda criteria for lymphoid and nonlymphoid murine malignancies.^25,26