Spatiotemporal analysis of illegitimate V(D)J deletions in Notch1 and Bcl11b genes (162.14)

Abstract

Abstract Aberrant V(D)J recombination events in oncogenes and tumor suppressor genes are implicated in development of T-cell leukemias and lymphomas. Previously, others identified hotspots for deletional DNA rearrangements adjacent to cryptic recombination signal sequences in Notch1 and Bcl11b genes in thymus of adult mice with radiation-induced thymic lymphomas. Interestingly, these rearrangements were also found at detectable frequencies in thymus of unirradiated WT animals suggesting that factors in addition to deletions contribute to development of lymphomas, but the frequency of deletions at different developmental stages or in peripheral lymphoid organs was not analyzed. To determine the timing, frequency, and tissue distribution of Notch1 and Bcl11b deletions during development, we are examining tissues harvested at different developmental stages from C57BL/6 mice. We detect these deletions in thymus at all ages examined from fetus to 6 months. Deletions are also detected in spleen, consistent with the presence of T cells bearing deletions in the circulating lymphocyte pool. We are analyzing sequences of deletion junctions for clonal relationships in individual animals and performing broken DNA end analysis for ongoing deletions. We are also using an inducible tetracycline-regulated RAG transgenic mouse system to determine if these rearrangements can occur at all ages with induced RAG expression or are limited to specific developmental windows.