Preprint identifies heterologous chromosome synapsis as a distinct, regulated mode of meiotic pairing in yeast

A bioRxiv preprint reports that heterologous synapsis — the formation of synaptonemal complex (SC) between non-homologous chromosome segments — is a regulated biological process distinct from canonical homologous synapsis, rather than merely a consequence of meiotic recombination defects.

The synaptonemal complex is a protein scaffold that aligns homologous chromosome pairs during meiosis and is required for crossover recombination and proper chromosome segregation. It has long been observed that when homologous recombination is impaired, SC forms promiscuously between non-homologous regions. Using budding yeast as a model organism, the authors demonstrate that this heterologous synapsis initiates through a pathway that operates in parallel to the well-established crossover-designated initiation sites — and that elements of it are also present transiently during wild-type meiosis at early stages.

The finding has implications for understanding the regulation of meiotic chromosome organisation, fertility genetics, and the origins of chromosomal abnormalities in gametes. It also raises questions about whether equivalent pathways exist in other organisms, including mammals. This is a preprint and has not yet undergone peer review.