SPO11-independent DNA repair foci and their role in meiotic silencing

PLoS Genet. 2013 Jun;9(6):e1003538. doi: 10.1371/journal.pgen.1003538. Epub 2013 Jun 6.

Abstract

In mammalian meiotic prophase, the initial steps in repair of SPO11-induced DNA double-strand breaks (DSBs) are required to obtain stable homologous chromosome pairing and synapsis. The X and Y chromosomes pair and synapse only in the short pseudo-autosomal regions. The rest of the chromatin of the sex chromosomes remain unsynapsed, contains persistent meiotic DSBs, and the whole so-called XY body undergoes meiotic sex chromosome inactivation (MSCI). A more general mechanism, named meiotic silencing of unsynapsed chromatin (MSUC), is activated when autosomes fail to synapse. In the absence of SPO11, many chromosomal regions remain unsynapsed, but MSUC takes place only on part of the unsynapsed chromatin. We asked if spontaneous DSBs occur in meiocytes that lack a functional SPO11 protein, and if these might be involved in targeting the MSUC response to part of the unsynapsed chromatin. We generated mice carrying a point mutation that disrupts the predicted catalytic site of SPO11 (Spo11(YF/YF)), and blocks its DSB-inducing activity. Interestingly, we observed foci of proteins involved in the processing of DNA damage, such as RAD51, DMC1, and RPA, both in Spo11(YF/YF) and Spo11 knockout meiocytes. These foci preferentially localized to the areas that undergo MSUC and form the so-called pseudo XY body. In SPO11-deficient oocytes, the number of repair foci increased during oocyte development, indicating the induction of S phase-independent, de novo DNA damage. In wild type pachytene oocytes we observed meiotic silencing in two types of pseudo XY bodies, one type containing DMC1 and RAD51 foci on unsynapsed axes, and another type containing only RAD51 foci, mainly on synapsed axes. Taken together, our results indicate that in addition to asynapsis, persistent SPO11-induced DSBs are important for the initiation of MSCI and MSUC, and that SPO11-independent DNA repair foci contribute to the MSUC response in oocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chromosome Pairing / genetics*
  • DNA Breaks, Double-Stranded
  • DNA Repair / genetics*
  • Endodeoxyribonucleases / genetics*
  • Endodeoxyribonucleases / metabolism
  • Female
  • Male
  • Meiosis / genetics*
  • Mice
  • Oogenesis / genetics
  • Spermatocytes / cytology
  • Spermatocytes / metabolism
  • X Chromosome / genetics
  • X Chromosome Inactivation / genetics*
  • Y Chromosome / genetics

Substances

  • Endodeoxyribonucleases
  • meiotic recombination protein SPO11

Grant support

This work was supported by the Netherlands Organization for Scientific Research (NWO) through ALW (VIDI 864.05.003 and Open Programme 819.02.020). BdM was supported by grants from the Centre National de la Recherche Scientifique (CNRS); the Association pour la Recherche sur le Cancer and the Agence Nationale de la Recherche (ANR-09-BLAN-0269-01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.