Post-meiotic DNA double-strand breaks are conserved in fission yeast

In mammals, spermiogenesis is characterized by transient formation of DNA double-strand breaks (DSBs) in the whole population of haploid spermatids. DSB repair in such haploid context may represent a mutational transition. Using a combination of pulsed-field gel electrophoresis and specific labelling of DSBs at 3'OH DNA ends, we showed that post-meiotic, enzyme-induced DSBs are also observed in the synchronizable pat1-114 mutant of Shizosaccharomyces pombe as well as in a wild-type strain, while DNA repair is observed at later stages. This transient DNA fragmentation arises in the whole cell population and is seemingly independent of the caspase apoptotic pathway. Because histones are still present in spores, the transient DSBs do not require a major change in chromatin structure. These observations confirm the highly-conserved nature of the process in eukaryotes and provide a powerful model to study the underlying mechanism and its impact on the genetic landscape and adaptation.