Oligopaint DNA FISH reveals telomere-based meiotic pairing dynamics in the silkworm, Bombyx mori

PLoS Genet. 2021 Jul 28;17(7):e1009700. doi: 10.1371/journal.pgen.1009700. eCollection 2021 Jul.

Abstract

Accurate chromosome segregation during meiosis is essential for reproductive success. Yet, many fundamental aspects of meiosis remain unclear, including the mechanisms regulating homolog pairing across species. This gap is partially due to our inability to visualize individual chromosomes during meiosis. Here, we employ Oligopaint FISH to investigate homolog pairing and compaction of meiotic chromosomes and resurrect a classical model system, the silkworm Bombyx mori. Our Oligopaint design combines multiplexed barcoding with secondary oligo labeling for high flexibility and low cost. These studies illustrate that Oligopaints are highly specific in whole-mount gonads and on meiotic squashes. We show that meiotic pairing is robust in both males and females and that pairing can occur through numerous partially paired intermediate structures. We also show that pairing in male meiosis occurs asynchronously and seemingly in a transcription-biased manner. Further, we reveal that meiotic bivalent formation in B. mori males is highly similar to bivalent formation in C. elegans, with both of these pathways ultimately resulting in the pairing of chromosome ends with non-paired ends facing the spindle pole. Additionally, microtubule recruitment in both C. elegans and B. mori is likely dependent on kinetochore proteins but independent of the centromere-specifying histone CENP-A. Finally, using super-resolution microscopy in the female germline, we show that homologous chromosomes remain associated at telomere domains in the absence of chiasma and after breakdown and modification to the synaptonemal complex in pachytene. These studies reveal novel insights into mechanisms of meiotic homolog pairing both with or without recombination.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bombyx / genetics*
  • Cell Cycle Proteins / genetics
  • Centromere / metabolism
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosome Pairing / genetics*
  • Chromosome Segregation / genetics
  • Chromosomes / genetics
  • DNA / genetics
  • Female
  • Male
  • Meiosis / genetics
  • Microtubules / metabolism
  • Synaptonemal Complex / metabolism
  • Telomere / genetics*

Substances

  • Cell Cycle Proteins
  • Chromosomal Proteins, Non-Histone
  • DNA

Grants and funding

This work was funded by the Intramural Program of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIDDK; DK015602 to E.P.L.), the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NICHD; 1K99HD104851 to L.F.R), LabEx DEEP grants from the Agence National de la Recherche (ANR-11-LABX-0044 and ANR-10-IDEX-0001-02 to I.A.D.), an ATIP-AVENIR research grant from CNRS/INSERM, the European Research Council (ERC; CENEVO-758757 to I.A.D.), and Institut Curie (I.A.D). NIDDK provides salary support for E.P.L. and L.F.R. Institute Curie and CNRS provide salary support for I.A.D. ERC provides salary support for J.G. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.