What can the water monster teach us about tissue regeneration in humans?
Based on two new studies by Salk researchers, regeneration of a new limb or organ in a human will be much more difficult than the mad scientist and supervillain, Dr. Curt Connors, made it seem in the Amazing Spider-Man comics and films.
As those who saw the recent movie, The Amazing Spider-Man, will know, Connors injected himself with a serum made from lizard DNA to successfully regrow his missing lower right arm—that is, before the formula transformed him into a reptilian humanoid.
But by studying a real lizard-like amphibian, which can regenerate missing limbs, the Salk researchers discovered that it isn't enough to activate genes that kick-start the regenerative process. In fact, one of the first steps is to halt the activity of so-called jumping genes.
In research published in both Development, Growth & Differentiation and Developmental Biology, the researchers showed that in the Mexican axolotl, an immature tadpole-like form of a salamander, jumping genes have to be shackled, or they might move around in the genomes of cells in the tissue destined to become a new limb and disrupt the process of regeneration. They found that two proteins, piwi-like 1 (PL1) and piwi-like 2 (PL2), perform the job of quieting down jumping genes in the axolotl—a creature whose name means water monster and who can regenerate everything from parts of its brain to eyes, spinal cord and tail.
"What our work suggests is that jumping genes would be an issue in any situation where you wanted to turn on regeneration," says the studies' senior author, Tony Hunter, a professor in the Molecular and Cell Biology Laboratory and director of the Salk Institute Cancer Center.
"As complex as it already seems, it might seem a hopeless task to try to regenerate a limb or body part in humans, especially since we don't know if humans even have all the genes necessary for regeneration," says Hunter. "For this reason, it is important to understand how regeneration works at a molecular level in a vertebrate that can regenerate as a first step. What we learn may eventually lead to new methods for treating human conditions, such as wound healing and regeneration of simple tissues."