Oxytocin is a hormone in the body that is known to play a key role in both physiology and behavior. However, it is currently unclear how this important signalling system evolved. Better understanding the evolution of this system can shed light on its current purpose. In a new study published in Communications Biology, led by PhD research fellow Alina M. Sartorius, we identified when genes involved in the oxytocin system first appeared on the evolutionary timeline.
We found that most of these genes (64%) are relatively 'modern' and appeared with or after the time that vertebrates (animals with backbones) and jawed vertebrates (animals with jaws) started to appear, that is between 540 – 25 million years ago. These modern genes include the main oxytocin receptor (OXTR), the gene that produces oxytocin (OXT), and a gene that regulates oxytocin secretion (CD38). Nearly half of these modern genes showed signs of having gone through significant evolutionary changes over time. We also found that 18% of the oxytocin genes are 'ancient', meaning they date back to the earliest cellular organisms, between 3.5 billion and 1.1 billion years ago. The remaining 18% of genes fell in between in terms of age and were categorized as 'medium-aged'.
When we looked at the functions that these genes regulate in humans, we found that the medium-aged genes are mostly active in organs that contract (like the uterus), while the modern genes are mainly active in the brain and muscles. Altogether, this research provided new insights into the complex evolutionary history of the oxytocin system and could have broader implications for understanding its diverse roles in human health and disease.
Full citation: Sartorius, A.M., Rokicki, J., Birkeland, S. et al. An evolutionary timeline of the oxytocin signaling pathway. Commun Biol 7, 471 (2024). https://doi.org/10.1038/s42003-024-06094-9