Why do some salamanders regenerate limbs faster than others? A team of biologists has identified genetic factors that may dictate the rate at which limbs and organs re-grow in these incredible amphibians, shedding much-needed light on one of the most remarkable physiological feats in the animal kingdom.
Few biological traits are more enviable than the salamander's capacity for regeneration. Missing limbs and damaged organs can be regrown and replaced without leaving so much as a scar. It's an anatomical feature we mammals sadly lack, yet some species of salamanders possess weaker regenerative powers than others, sprouting body parts more slowly than their more resilient relatives. Still others lose their regenerative capacity as they age.
Not a lot is known, on the genetic level, about salamanders' variable regenerative abilities. Understanding why the pace of limb growth differs within and between species – and why it can decline over time – could help paint a clearer picture of regeneration's underlying mechanisms, while inching us closer to a time when we might harness this power for ourselves.
Now, members of the University of Kentucky Department of Biology & Spinal Cord and Brain Injury Research Center have linked the salamanders' ability to regenerate a severed tail with several segments of genetic code thought to affect tail-width.
By monitoring the rate of tail regrowth in over 200 salamanders and comparing their genomes, a team led by salamander regeneration expert S. Randal Voss was able to identify genetic factors associated with variations in tail morphology and regeneration. In today's issue of PLoS ONE, the researchers report that "tail width at the sight of injury explains the majority of variation in regenerative outgrowth," and that this tail-width, in turn, is associated with a suite of genetic factors, most notably a sex-determining DNA sequence called ambysex.
"Although salamander tail regeneration has been studied for almost 300 years, many fundamental questions remain unanswered," write the researchers. And while they note that further investigation is needed to examine "quantitative effects of cells, tissues, and molecules on regenerative outgrowth," the team's findings represent an important step in the process of elucidating what separates salamanders from the rest of us.
The researchers' findings are published free of charge in the latest issue of PLoS ONE.