Single-cell mapping of chromosome breaks identifies multiple fragile site classes with distinct DNA replication timing landscapes.

Single-cell mapping reveals that 42% of chromosome breaks in human cells occur at common fragile sites, with 58% occurring at rare, replication-timing-dependent regions.

• Why it matters: Understanding the full spectrum of fragile sites is crucial for comprehending genome stability and the mechanisms underlying chromosome breakage, especially under replication stress.
• What they did: Researchers performed single-cell genome-wide mapping of aphidicolin-induced breaks in human osteosarcoma cells, classifying breaks based on replication timing and transcription dependence, identifying multiple break classes.
• The result: Findings show distinct replication timing landscapes and mechanistic features for each break class, advancing knowledge of genomic fragility and potential targets for genomic stability interventions.