Cell Type-Specific Double Strand Break Repair: An Inter-chromosomal Homologous Recombination Study using the Rainbow Mouse Model

Faithful repair of DNA lesions is central to maintaining genomic integrity. Illegitimate repair of chromosomal DNA damage, especially double-strand breaks (DSBs), can lead to mutations and genome rearrangements. Homologous recombination (HR) is a highly conserved molecular process that plays an important role in the repair of DSBs and the maintenance of genome stability. However, it is not fully understood which cell populations at which developmental stages in vivo have the potential to use this “error-free” repair mechanism. Further, although HR is considered to be “error-free”, illegitimate inter-chromosomal HR has been linked to the formation of chromosomal translocations that are a hallmark of leukemias, lymphomas, and sarcomas. For my studies, I engineered a transgenic mouse “Rainbow Mouse” model to induce specific chromosomal DSBs in vivo and score for inter-chromosomal HR repair in multiple tissues and cell types. I used the Rainbow Mouse to address critical biological questions- What is the relative frequency of inter-chromosomal HR repair among different tissue subpopulations? Which cell types are more likely to utilize this mechanism? Can DSBs induced in utero be repaired by inter-chromosomal HR repair? I hypothesized a significant difference in inter-chromosomal HR observed in different cell types based on their cellular differentiation state.
Overall, my research demonstrates a function reporter model to evaluate inter-chromosomal HR in vivo. My research identified specific cell types, such as pancreatic duct cells and hematopoietic stem cell enriched LIN-/CD34+ populations that undergo DSB-induced inter-chromosomal HR leading to mutation. The findings from my research highlight developmental and cell type-specific differences in the potential for inter-chromosomal HR to be used in the repair of DSBs. The Rainbow mouse model utilized in this study has the potential for long-term application in assessing the mutagenic effects of various environmental and dietary compounds, as well as understanding the role of specific proteins involved in repairing DNA damage induced by these compounds.