Insertions in the Ebf1 gene. Three Etv6^+/RUNX1; T2Onc^+/Tg (EROnc) mice (129753, 132799, and 129713) that developed BCP-ALL carried insertions in the Ebf1 gene (indicated by the red triangles in introns 6 and 8). Sequencing of the insertion-genome junction from splenic cDNA of these mice showed the splicing of Ebf1 directly onto the SA-polyA from the transposon. Although sample 129713 carried an insertion in intron 8, we detected splicing onto the transposon directly from exon 6.