Ask the Experts: Growing new limbs

A reader sent me the following question:

"How does a lizard grow a new tail?"

This was a very timely question as new research has shed light on this very phenomenon. A team of experts at Arizona State University led by Dr. Kenro Kusumi and colleagues have been studying limb regeneration in lizards.

Green anole lizard (Anolis carolinensis) with tail a new tail (image credit: Hutchins et al./PLoS ONE)

The green anole lizard (pictured above) can lose its tail when captured by a predator. They are then able to regrow their tails, although they do not look quite like the original. Dr. Kusumi's team characterized the genes that are turned on during this regeneration process.

According to Dr.  Kusumi, "Lizards are the most closely-related animals to humans that can regenerate entire appendages. We discovered that they turn on at least 326 genes in specific regions of the regenerating tail, including genes involved in embryonic development, response to hormonal signals and wound healing.”

While frog tadpoles and fish can likewise regrow the tips of their tails, lizard regrowth is not limited to the tip, but rather appears to be distributed throughout the length of the tail. Study co-author Elizabeth Hutchins (a graduate student at Arizona State University who contributed to this research) said that it can take more than 60 days for a lizard to regrow a functional tail.

The implications for this research in developing methods to regrow limbs in humans is pretty exciting! Dr. Kusumi mentioned, "Using next-generation technologies to sequence all the genes expressed during regeneration, we have unlocked the mystery of what genes are needed to regrow the lizard tail. By following the genetic recipe for regeneration that is found in lizards, and then harnessing those same genes in human cells, it may be possible to regrow new cartilage, muscle or even spinal cord in the future."

Sources:

Arizona State University Press Release

Hutchins ED, Markov GJ, Eckalbar WL, George RM, King JM, Tokuyama MA, Geiger LA, Emmert N, Ammar MJ, Allen AN, Siniard AL, Corneveaux JJ, Fisher RE, Wade J, DeNardo DF, Rawls JA, Huentelman MJ, Wilson-Rawls J, Kusumi K. Transcriptomic Analysis of Tail Regeneration in the Lizard Anolis carolinensisReveals Activation of Conserved Vertebrate Developmental and Repair Mechanisms. PLOS ONE.  9(8): e105004. doi:10.1371/journal.pone.0105004