The Sleeping Beauty (SB) transposon system is a powerful system for studying insertional mutagenesis in fish and it has been recently adapted to the mouse. This system allows rapid and accurate identification of genetic lesions that may drive the initiation and progression of diseases such as cancers. In this study, we performed a SB transposon mutagenesis experiment to characterize the genes and pathways that are associated with the development of erythro-megakaryocytic leukemia, a leukemia subtype that is currently being poorly understood1 . A genome-wide bioinformatic analysis was performed to discover common insertion sites (CISs) of the SB transposons in a number of tumors.
We performed Roche 454 sequencing for forty JAK2SBvav mice that developed erythro-megakaryocytic leukemia. The 454 sequencer produces long sequence reads (~300bp on average) which allow us to map them back to the genome and to find transposon insertion loci. We used the Subread aligner, a high-performance read aligner developed by ourselves, for the read mapping. This aligner is particularly powerful for mapping long reads. Read mapping is critical for the success of this project because incorrect read alignments can easily give rise to false CIS calls. After read mapping, we performed a rigorous statistical testing to call CISs.
A number of CISs were discovered, including members of ETS family of transcription factors : Erg and Ets1, which were discovered in 88% and 65% leukemias, respectively. The leukemia-causing potential of discovered CISs were validated by a further sequencing experiment in which mice were infected with a retrovirus expressing GFP plus TLS-ERG, a leukemia-derived product of intragenic translocation of ERG. The exciting discovery from this project opens the possibility of developing new treatments for erythro-megakaryocytic leukemia.