Project description:ABSTRACT Aims: Double-stranded breaks (DSBs) cause genomic instability, a hallmark of aging, and activate the DNA damage response (DDR) and the cytosolic DNA-sensing proteins (CDSP) pathways. The activated pathways induce cell cycle arrest, inflammation, senescence, cell death, fibrosis, and organ dysfunction. The purpose of the study was to identify and characterize genome-wide DSBs at the nucleotide resolution in adult cardiac myocytes. Methods and Results: We identified the genome-wide DSBs in the genomes of ~ 6 million adult cardiac myocytes (1 million per sample) in the 3 wild-type and 3 myocyte-specific LMNA-deficient mice (Myh6-Cre:LmnaF/F) mice by END-Sequencing. We identified 6,774 differential DSBs between the wild-type and Myh6-Cre:LmnaF/F cardiac myocytes, which, except for 8, were exclusive to the Myh6-Cre:LmnaF/F genotype. The differential DSBs were enriched in the gene regions, transcription initiation sites, cardiac transcription factor motifs, and at the G quadruplex forming structures, suggesting the involvement of the transcriptional stress. Because LMNA regulates transcription, we performed a CUT&RUN assay with an anti-LMNA antibody (N=5) to test the role of transcriptional stress in an increased prevalence of DSBs. We identified an average of 818 genome-wide lamin-associated domains (LADs), which encompassed 30% of the mouse genome. LADs were associated with a 16-fold reduction in the transcript levels of protein-coding genes located at the LAD regions (N=3,975) as opposed to genes located at the non-LAD regions (N=~ 17,778). Consistent with increased transcription at the non-LAD regions DSBs were ~ 6-fold more prevalent in the non-LAD than LAD regions. Likewise, the loss of LAD was associated with a 2.3-fold higher prevalence of differential DSBs in the Myh6-Cre:LmnaF/F cardiac myocyte genomes, which were predominantly localized to the transcription start sites. Conclusions: To our knowledge, this is the first identification of the DSBs, a hallmark of aging, at the nucleotide resolution in the cardiovascular system. The findings implicate transcriptional stress in the pathogenesis of DSB and the protective role of LMNA against DSBs likely through transcriptional suppression. Given the ubiquitous nature of transcriptional stress, DSBs are expected to be pervasive and pathogenic through activation of the DDR and CDSP pathways not only in cardiovascular diseases but also in other conditions, including aging.
Project description:Single Centre, open label assignment phase II clinical study.
To evaluate the effect of oral 200mg Methylene Blue tablets (administered 8x25mg) prior to endoscopy on double stranded DNA breaks in colonic biopsy samples assessed by histone gamma H2AX analysis, compared to control biopsies.
Project description:Goal is to analyze the expression profile of cells shortly after induction of mitochondrial double stranded breaks. ARPE-19 cells are transfected with constructs coding for mitochondrial TALENs, either active or dead. These constructs target two different locations of mtDNA (ATP8 and Dloop). Gene expression is then compared between untransfected and transfected cells (either active or dead TALENs), or between active TALEN (cells with mitochondrial double stranded breaks) and dead TALEN (expressing the same protein without cutting the mitochondrial genome)
Project description:Doxorubicin is a widely used chemotherapeutic drug that intercalates between DNA base-pairs and posions Topoisomerase II, although the mechanistic basis for cell killing remains speculative. Here we show that both anthracyclines and Topoisomerase II poison cause enhanced DNA double-strand breaks around CpG island promoters of active genes genome-wide. We propose that torsion-based enhancement of nucleosome turnover exposes promoter DNA, ultimately causing DNA breaks around promoters that contributes to cell killing. We have analyzed mouse squamous cell carcinoma cells treated with doxorubicin, aclarubicin and etoposide. The direct in situ Breaks Labeling, Enrichment on Streptavidin (BLESS, PMID 23503052) method was used for mapping DNA double-strand breaks genome-wide.
Project description:We describe a robust linear amplification-mediated high-throughput genome-wide translocation sequencing (HTGTS) method that identifies endogenous or ectopic "prey" DNA double-stranded breaks (DSBs) across the human genome based on their translocation to "bait" DSBs generated by engineered nucleases. HTGTS with different Cas9:gRNA or TALEN-nuclease on-target baits revealed off-target hotspots for given nucleases that ranged from few or none to dozens or more, and greatly extended known off-target numbers for certain previously characterized engineered nucleases by more than 10-fold. Beyond various types of nuclease off-target collateral damage, we also identified collateral damage in the form of translocations between bona fide nuclease targets on homologous chromosomes. Based on frequent non-specific DSBs making any given human chromosome an HTGTS hotspot region for bait DSBs within it, we found that HTGTS also reveals wide-spread, low-level DSB-generating activities of engineered nucleases. Finally, HTGTS confirmed that the Cas9D10A paired nickase approach suppresses off-targets genome-wide and suggested other strategies to enhance desired nuclease activities.
Project description:Doxorubicin is a widely used chemotherapeutic drug that intercalates between DNA base-pairs and posions Topoisomerase II, although the mechanistic basis for cell killing remains speculative. Here we show that both anthracyclines and Topoisomerase II poison cause enhanced DNA double-strand breaks around CpG island promoters of active genes genome-wide. We propose that torsion-based enhancement of nucleosome turnover exposes promoter DNA, ultimately causing DNA breaks around promoters that contributes to cell killing.
Project description:DNA double-strand breaks (DSBs) and their repair can cause extensive epigenetic changes. As a result, DSBs have been proposed to promote transcriptional and, ultimately, physiological dysfunction via both cell-intrinsic and cell-non-autonomous pathways. Studying the consequences of DSBs in higher organisms has, however, been hindered by a scarcity of tools for controlled DSB induction. Using a mouse model for both tissue-specific and temporally controlled DSB formation, we investigated the transcriptional response to break repair. Transcriptional profiling of lymphocytes in spleen and thymus by RNA-Seq, with and without I-PpoI knock-in.