Earth is a treasure trove of biodiversity, with over 8.7 million known species alive today, and that only represents an estimated 20 percent of all of the existing species that currently exist. But despite the sheer diversity of lifeforms, be it plant, animal, or microbe, we all share a common single-celled ancestor that started to diverge into new species 1.6 billion years ago. And because of that common ancestor, all species have a lot in common when it comes to our DNA: chimpanzees are nearly genetically identical to us; we share 69 percent of our genetic makeup with the otherwise oddball platypus; and we have even one-quarter of our code in common with rice.
But, as evolution would have it, as different species emerged, each came with a different set of traits, including extremely useful abilities such as being able to regenerate lost limbs. It was the possibility of humans still sharing DNA with species that can regenerate missing body parts that prompted two researchers from Maine’s MDI Biological Laboratory to compare the genetic codes responsible for that regeneration of three such species: the Mexican axolotl salamander; the ray-finned bichir, a fish from Africa; and the zebrafish, common to India. And the similarities between the species’ was striking.
“I remember that day very well — it was a fantastic feeling,” remarks Benjamin L. King, one of the researchers. “We didn’t expect the patterns of genetic expression to be vastly different in the three species, but it was amazing to see that they were consistently the same.”
The axolotl, bichir and zebrafish all shared a common ancestor that they split from roughly 420 million years ago, but their evolution saw fit to keep the same genetic code responsible for regrowing limbs. The researchers hope that this new finding will help shed light on not only how other species regenerate tissue, but also why humans don’t have that ability, and hopefully to develop therapies that can trigger that level of regeneration in patients that require that level of healing.
“Limb regeneration in humans may sound like science fiction, but it’s within the realm of possibility,” explains co-researcher Voot P. Yin. “The fact that we’ve identified a genetic signature for limb regeneration in three different species with three different types of appendages suggests that nature has created a common genetic instruction manual governing regeneration that may be shared by all forms of animal life, including humans.”