A University of Utah-led research team announced on Mar. 11 that they have uncovered the mechanism by which so-called “selfish chromosomes” manipulate genetic inheritance, using the Overdrive (Ovd) gene to destroy competing sperm cells.
The discovery sheds light on a long-standing evolutionary puzzle about how certain genes can bias inheritance in their favor, defying the typical 50/50 odds predicted by Mendelian genetics. This process, known as segregation distortion, has been observed across many animal species but its underlying biology remained unclear until now.
According to the researchers, Ovd normally acts as a quality control checkpoint during sperm development, eliminating abnormal sperm cells. However, selfish chromosomes exploit this system to kill off healthy rivals and increase their own chances of being passed on to the next generation. The team found this mechanism at work in two different Drosophila species with unrelated selfish chromosomes, suggesting that multiple genetic systems may independently evolve to use the same pathway.
“This is the first time that the same gene has been shown to be crucial for eliminating gametes by multiple independent selfish chromosomes,” said Jackson Ridges, University of Utah biologist and lead author of the study. “It indicates that evolutionarily distant selfish chromosomes may often converge on shared cellular processes.”
Nitin Phadnis, associate professor at the University of Utah and senior author of the study, said: “How selfish genes can cause sterility has been a long-standing mystery in field of speciation. By going for a deep understanding of how Overdrive works, we inadvertently opened up entirely new directions of research into understanding the mechanisms of cellular quality control systems, and how sterility emerges between young species.”
The findings could also provide insights into male infertility and reproductive barriers between species. While humans do not have an exact equivalent to Ovd, similar quality-control processes may exist using different genetic machinery.
The research was published on Feb. 10 in Nature Communications. The team plans further studies knocking out Overdrive in other Drosophila species and investigating whether similar segregation distortion occurs in human lineages.