Cell transcriptional state alters genomic patterns of DNA double-strand break repair in human astrocytes

The misrepair of DNA double-strand breaks in close spatial proximity within the nucleus can result in chromosomal rearrangements that are important in the pathogenesis of hematopoietic and solid malignancies. It is unknown why certain epigenetic states, such as those found in stem or progenitor cells, appear to facilitate neoplastic transformation. Here we show that altering the transcriptional state of human astrocytes alters patterns of DNA damage repair from ionizing radiation at a gene locus-specific and genome-wide level. Astrocytes induced into a reactive state exhibited increased DNA repair, compared to non-reactive cells, in actively transcribed chromatin domains after irradiation. In mapping these sites of repair, we identified misrepair events and repair hotspots that were unique to each state. The precise characterization of genomic regions susceptible to mutation in specific epigenetic transcriptional states provides new opportunities for addressing clonal evolution in solid cancers, particularly those where double-strand break induction is a cornerstone of management. Primary astrocyte cells were cultured to confluency and went through a linear monolyer scratch or no scratch.