Alignment of Homologous Chromosomes and Effective Repair of Programmed DNA Double-Strand Breaks during Mouse Meiosis Require the Minichromosome Maintenance Domain Containing 2 (MCMDC2) Protein

PLoS Genet. 2016 Oct 19;12(10):e1006393. doi: 10.1371/journal.pgen.1006393. eCollection 2016 Oct.

Abstract

Orderly chromosome segregation during the first meiotic division requires meiotic recombination to form crossovers between homologous chromosomes (homologues). Members of the minichromosome maintenance (MCM) helicase family have been implicated in meiotic recombination. In addition, they have roles in initiation of DNA replication, DNA mismatch repair and mitotic DNA double-strand break repair. Here, we addressed the function of MCMDC2, an atypical yet conserved MCM protein, whose function in vertebrates has not been reported. While we did not find an important role for MCMDC2 in mitotically dividing cells, our work revealed that MCMDC2 is essential for fertility in both sexes due to a crucial function in meiotic recombination. Meiotic recombination begins with the introduction of DNA double-strand breaks into the genome. DNA ends at break sites are resected. The resultant 3-prime single-stranded DNA overhangs recruit RAD51 and DMC1 recombinases that promote the invasion of homologous duplex DNAs by the resected DNA ends. Multiple strand invasions on each chromosome promote the alignment of homologous chromosomes, which is a prerequisite for inter-homologue crossover formation during meiosis. We found that although DNA ends at break sites were evidently resected, and they recruited RAD51 and DMC1 recombinases, these recombinases were ineffective in promoting alignment of homologous chromosomes in the absence of MCMDC2. Consequently, RAD51 and DMC1 foci, which are thought to mark early recombination intermediates, were abnormally persistent in Mcmdc2-/- meiocytes. Importantly, the strand invasion stabilizing MSH4 protein, which marks more advanced recombination intermediates, did not efficiently form foci in Mcmdc2-/- meiocytes. Thus, our work suggests that MCMDC2 plays an important role in either the formation, or the stabilization, of DNA strand invasion events that promote homologue alignment and provide the basis for inter-homologue crossover formation during meiotic recombination.

MeSH terms

  • Animals
  • Cell Cycle Proteins / genetics
  • Chromosome Segregation / genetics
  • DNA Breaks, Double-Stranded*
  • DNA Repair / genetics
  • Homologous Recombination / genetics*
  • Male
  • Meiosis / genetics*
  • Mice
  • Minichromosome Maintenance Proteins / genetics*
  • Nuclear Proteins / genetics
  • Oocytes / metabolism
  • Phosphate-Binding Proteins
  • Rad51 Recombinase / genetics
  • Recombinant Proteins / genetics*
  • Sequence Alignment
  • Spermatocytes / metabolism

Substances

  • Cell Cycle Proteins
  • Dmc1 protein, mouse
  • MCMDC2 protein, mouse
  • Nuclear Proteins
  • Phosphate-Binding Proteins
  • Recombinant Proteins
  • Rad51 Recombinase
  • Minichromosome Maintenance Proteins

Grant support

A wrap-up grant of the Graduate academy of the TU Dresden (https://tu-dresden.de/die_tu_dresden/zentrale_einrichtungen/graduiertenakademie/ueber_uns/ziele/document_view?set_language=en) supported FF. Dresden International Graduate School for Biomedicine and Bioengineering (http://www.dresden-ipp.de/partners/digs-bb/) supported MS and ID by the Wrap-up program and PhD bridging funds, respectively. Deutsche Forschungsgemeinschaft, www.dfg.de/en/ (grants: TO421/3-2, SPP1384:TO421/4-2, TO421/5-1, TO421/6-1, TO421/8-1 and 8-2) supported FF, RR, ID, MS, DT, and AT. The funds were received by AT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.