Condensin I complex shown to control higher-order chromosome structure and recombination in male meiosis

Researchers have posted a preprint to bioRxiv examining the role of the condensin I complex in organising chromosomes during meiosis — the specialised cell division that produces sperm and eggs. The study focusses on NCAPD2, a subunit of the SMC-condensin I complex, which shapes chromatin through a process called loop extrusion.

Meiotic chromosomes adopt a characteristic axis-loop architecture in prophase I — the stage at which homologous chromosome pairs align and exchange genetic material through homologous recombination. Accurate recombination is essential for generating genetic diversity and for ensuring that chromosomes segregate correctly into gametes. Failures in this process can lead to infertility or chromosomally abnormal offspring.

Using mouse models, the authors demonstrate that NCAPD2 colocalises with prophase I chromatin and that its loss results in male infertility. The data implicate condensin I in establishing the higher-order chromatin loop structure required for normal synapsis — the close pairing of homologous chromosomes via the synaptonemal complex — and for faithful homologous recombination.

The condensin complexes (condensin I and condensin II) have well-established roles in mitotic chromosome compaction, but their contributions to meiotic chromosome structure have been less thoroughly characterised in mammals. This study adds to an emerging picture in which chromatin loop extrusion machinery plays active roles in the meiotic programme. The preprint has not yet been peer-reviewed.