Discovering How Chromosomes Pair During Sperm Formation

Chromosomes are shown in blue, pink, and yellow during various stages of prophase and prometaphase. The nuclei are arranged in a circular clock pattern.
Meiotic pairing in a pantry moth model.
Credit: Rosin Lab, NICHD/NIH

During the creation of egg or sperm cells—a specialized cell division called meiosis—homologous chromosome pairs (one maternal and one paternal copy) need to find each other for genetic recombination before the cell divides. One of the biggest mysteries in biology is understanding how chromosomes find each other and distinguish homologs from other chromosomes. To facilitate meiosis, homologous partners pair up from end to end, undergo an exchange of genetic information, and then large protein complexes called kinetochores are formed to enable chromosome segregation.

In a study from the Rosin Lab, researchers investigated how homologs pair and how kinetochores form during spermatogenesis in two different moth species: the pantry moth, Plodia interpunctella, and the silkworm moth, Bombyx mori, which diverged from P. interpunctella over 100 million years ago.
Using a combination of microscopy methods, the team observed that homologs seem to pair via interactions at chromosome ends.
Conversely, kinetochores formed at chromosome centers, away from chromosome ends. This is true even when chromosomes were folded into different configurations.
They also found that central kinetochores are functional and can recruit microtubules, the structures that physically pull chromosomes apart for segregation.
Overall, the findings challenge a classical view of kinetochore/microtubule dynamics during chromosome segregation and highlight the importance of exploring fundamental processes in non-standard systems, as employing novel organisms can lead to the discovery of novel biology.

Reference

Hockens C, Lorenzi H, Wang TT, Lei EP, and Rosin LF. Chromosome segregation during spermatogenesis occurs through a unique center-kinetic mechanism in holocentric moth species. PLOS Genetics DOI: 10.1371/journal.pgen.1011329 (2024)

Learn more about the Genetics and Epigenetics of Development Group:
https://www.nichd.nih.gov/about/org/dir/affinity-groups/GED.