Concerted cutting by Spo11 illuminates DNA break mechanisms and initiates gap repair during meiosis

Genetic variation arises during meiosis via repair of DNA double-strand breaks (DSBs) created by the topoisomerase-like Spo11 protein. These DSBs are thought to always occur sparsely across the genome, with isolated DSBs generating discrete recombination events. We challenge this view, demonstrating that hyper-localised coincident DSBs frequently form within hotspots in both S. cerevisiae and mouse - a process suppressed by the DNA damage response kinase Tel1/ATM. Remarkably, the distances separating coincident DSBs vary with ~10.5 bp periodicity, invoking a model where adjacent Spo11 molecules have a fixed orientation relative to the DNA helix. Deep sequencing of meiotic progeny identifies recombination scars consistent with gap repair initiated by adjacent DSBs. Our results revise current thinking about how genetic recombination initiates, reviving original concepts of meiotic recombination as double-strand gap repair.