Precise homolog pairing is essential for accurate meiotic chromosome segregation in species from plants to humans. Failure to accurately segregate chromosomes in meiosis can lead to nondisjunction and infertility or aneuploidy in progeny. Yet, the mechanisms regulating homolog recognition and pairing are unknown. This has been particularly mysterious since the discovery that homolog recognition and alignment are independent of DNA double-strand breaks (DSBs) in most species. Instead, DSBs are required to form crossovers, which help stabilize pairing interactions after they are established.

We previously employed the highly specific Oligopaint fluorescence in situ hybridization (FISH) technology to interrogate homolog recognition and pairing initiation in the silkworm moth Bombyx mori (Rosin et al., 2021, PLOS Genetics) and recently have expanded these studies to the Indianmeal moth Plodia interpunctella. Our studies in Bombyx revealed that meiotic pairing in male moths occurs asynchronously through numerous partially paired intermediate structures. Similar to findings from the nematode C. elegans, we found that meiotic pairing in moths is initiated at chromosome ends. However, unlike C. elegans, chromosome ends in moths are not necessarily gene-poor, and gene-rich chromosome ends pair earlier than gene-poor ends. Furthermore, gene-rich chromosomes initiate pairing earlier than gene-poor chromosomes. This supports a model where transcriptional potential mediates homolog recognition.

One of our current research goals is to investigate the mechanisms behind this gene-rich-associated pairing and investigate whether transcription, the transcription machinery, or transcripts themselves facilitate homolog recognition and meiotic pairing initiation in moths and beyond.

Left: IF/FISH in a prophase I spermatocyte (pachytene) from Bombyx mori larval testes. A single whole chromosome is labeled with Oligopaints (magenta), telomeric repeats are labeled by DNA FISH in yellow, the synaptonemal complex is shown in cyan (Hop1; antibody from Scott Hawley lab; unpublished), and DAPI (DNA) is shown in blue.