A Blueprint to Regenerate Limbs

In its own way, the axolotl salamander is a mighty beast. Chop off its leg, and the gilled creature will grow a new one. Freeze part of its heart, and the organ will form anew. Carve out half of its brain, and six months later, another half will have sprouted in its place. “You can do anything to it except kill it, and it will regenerate,” says Gerald Pao, a postdoctoral researcher at the Salk Institute for Biological Studies, in La Jolla, CA.

That extraordinary power of regeneration inspired Pao and his collaborator Wei Zhu, also at the Salk Institute, to probe the axolotl salamander’s DNA. Despite decades of research on the salamander, little is known about its genome. That began to change last year, when Pao and his collaborators won one billion bases’ worth of free sequencing from Roche Applied Science, based in Penzberg, Germany. Now that the data is in, scientists can finally begin the hunt for the genetic program that endows the animal with its unique capabilities.

While all animals can regenerate tissue to a certain extent–we can grow muscle, bone, and nerves, for example–salamanders and newts are the only vertebrates that can grow entire organs and replacement limbs as adults. When a leg is lost to injury, cells near the wound begin to dedifferentiate, losing the specialized characteristics that made them a muscle cell or bone cell. These cells then replicate and form a limb bud, or blastema, which goes on to grow a limb the same way that it forms during normal development.

Scientists have identified some of the molecular signals that play a key role in the process, but the genetic blueprint that underlies regeneration remains unknown. Researchers hope that by uncovering these molecular tricks, they can ultimately apply them to humans to regrow damaged heart or brain tissue, and maybe even grow new limbs.

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If we can regenerage anything we like in the future, is it likely that we will stick to just limbs?

I don’t think so.

We’ll likely use this technology to ‘redecorate’ our aging, internal machinery as well… potentially prolonging our lives indefinitely.

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