Scientists have just discovered how certain animals manage to regrow missing limbs or fins. In a paper just published in PLoS ONE, researchers studied three animals with regenerative properties. They learned that these animals shared similar microRNA sequences even though they had diverged in evolution hundreds of millions of years ago.
The researchers studied three animal species that all have the ability to regenerate after an injury. The zebrafish, Danio rerio, is a commonly studied fish that can regrow its caudal fins. The bichir, Polypterus senegalus, is a primitive, air-breathing fish that is able to regrow its pectoral fins. The axolotl, Ambystoma mexicanum, is an amphibian with external gills and the capability to regenerate its forelimbs. All three animals use stem cells to regenerate missing body parts after an injury, such as an attack by a predator. Until now, scientists didn’t know the genetic mechanisms behind this process.
The scientists amputated the appendages of the three animals and then analyzed the RNA at the site of the amputation. They found a shared group of microRNA sequences being used to control regeneration in all three species. MicroRNA molecules are small, noncoding sequences of RNA that are used to regulate gene expression. The animal species studied were regenerating different body parts using separate biological processes yet all relied on these same microRNA sequences.
Zebrafish, bichirs, and axolotls have not shared a common ancestor since 420 million years ago. These new findings suggest that the ability to regenerate limbs is not a trait that evolved independently in multiple animals. Instead, all three animals rely on the same set of microRNA to regulate the proper genes. Some of these sequences are even conserved in the human genome. The authors are hopeful that this could lead to new breakthroughs in human medicine, especially in the treatment of injuries.
King BL, Yin VP. A Conserved MicroRNA Regulatory Circuit Is Differentially Controlled during Limb/Appendage Regeneration. PLoS ONE (2016).