Comprehensive Mapping of Transposon Insertions in Human Hematopoietic Neoplasias.

Abstract 1103

Poster Board I-125

Our genomes are replete with mobile DNAs, many of which are retrotransposons that have accumulated over time by “copy-and-paste” mechanisms involving reverse transcription of RNA intermediates. Subsets of human transposable elements have been recently active or remain active today, resulting in many insertional polymorphisms in modern populations. In vitro studies in human tumor cell lines have unequivocally shown that expressed retrotransposons can generate new insertions and potentiate large scale genomic rearrangements. Though normally transposon sequences are highly methylated and thus stably suppressed in somatic cells, loss of methylation has been described in some malignant states, including chronic lymphocytic leukemia (CLL), multiple myeloma (MM), and ‘blast crisis’ phase chronic myeloid leukemia (CML). This has led to speculation that derepressed transposons contribute to clonal evolution of these pathologies, though experimental evidence for this has been lacking due to an inability to detect new genomic insertions. In collaboration with Jef Boeke's laboratory, I have developed an array-based transposon insertion profiling method (TIP-chip) for mapping mobile retrotransposons in the human genome. Early application of this technology in leukemia patients and leukemia cell lines shows numerous novel insertions of L1 LINEs, AluYb SINEs, and HERV-K transposons, including several insertions in genes known to be involved in leukemogenesis. We expect the technology will add a new dimension to our understanding of the human genome, including genetic predispositions to cancer development, and will enable tests of the hypothesis that insertional mutagenesis by endogenous transposons is a driving force in hematopoietic malignancies.