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The Man of Steel, Myostatin, and Super Strength

The views expressed are those of the author and are not necessarily those of Scientific American.


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As an infant, the Man Of Steel escaped Krypton’s red sun in a rocket lovingly prepared for him by his parents. Kal-L (but more commonly known as Kal-El) arrived under our yellow sun in Smallville to eventually become Clark Kent. Since his debut in Action Comics #1 in June of 1938, Superman has accumulated a pretty long list of “super abilities”.

For me, though, I really like the list of his abilities that come from the 1940s radio serials. This was back when Superman was described as “faster than a speeding bullet, more powerful than a locomotive, and able to leap tall buildings in a single bound”. These descriptions all have to do with super-strength when you get right down to it. And with this summer’s “Man of Steel” Superman re-boot, super-strength is the focus of this post.

I have to admit I’ve always found the explanation for Superman’s powers to be, well, a bit dubious. He has his powers because of our yellow sun. That is, because he was from a red sun planet (Krypton) somehow the yellow sun of Earth unleashes some inner super power mechanism that gives Superman all his…super-ness. Of course it’s a bit pure escapist fun. But what if there actually was something to that, though?

I don’t mean something to the “yellow sun / red sun” stuff. You can just check in with our “friendly neighborhood physics” professor Jim Kakalios and his bok “Physics of Superheroes” for the real deal on that one. I mean rather the unleashing of some inner mechanism bit. What if something inside the human body could be unleashed—like removing the shackles from Hercules—and allow for dramatically increased strength?

Which brings me to two proteins with the superhero sounding names of myostatin and activin A. These are “chalones”—factors secreted by your cells to suppress excessive growth of an organ—found in your muscles. They basically work to keep the size and number of your muscle cells—and thus your overall strength—within a certain range. Since these factors work to negatively regulate muscle cell growth, removal of these factors allows muscle cells to get larger and increase in number. That’s where the “super-strength” comes from!

The Source of Super-Strength Here On Earth…

Myostatin itself has a pretty interesting history in animal husbandry and selective breeding. Although it didn’t go by the name myostatin back then, the effect of this growth factor was first described in cattle as “bovine muscular hypertrophy” by the British farmer H. Culley in 1807. Cattle that have a myostatin gene deletion look unusually and excessively muscular. So much so that the term “double muscled” is often used because of the look and the reality that such a cow has less bone, less fat and much more muscle than a “normal” cow.

This mutation, and more recently that of activin A, has been shown in many mammals so far, including rodents, dogs, pigs, sheeps, and—wait for it—humans. In fact I used this as partial basis for a genetic basis for Batman’s abilities in my first book.

The best example of myostatin gene deletions in humans was provided by Schuelke and colleagues back in 2004. The figure comes from that study and shows the image of the child at 6 days old (left side) and at 7 months (right). Arrowheads point to clear increases in muscle tissue at the hip and lower leg. The ultrasound images show the areas and sizes of the muscles (F=femur bone, VL, VI, VM, and RF are all parts of the ‘quadriceps’ knee extensor muscle group) for the child with the mutation (left) and a child of the same age without the mutation. This boy continued to develop normally but with greatly enhanced strength. In fact, at the age of 4½ this child could hold two 3 kg dumbbells with arms straight out to the sides!

But, there’s more. The story so far…your strength is a function of the number and size of your muscle cells. And the size and number of your muscle cells is regulated by myostatin and activin A. What if there was something that also guarded the guards? Well, it appears follistatin might fit that requirement. This means there could be a way to turn off the genetic switch that keeps muscle strength in check. Maybe.

Superhero Genetic Engineering… What Do We Want To Super-Charge?

Recent advances have decoded genes related to high performance in many bodily systems in humans. This gives us a kind of road map over what we want to mutate on purpose. Super-strength is a good place to start.

First of all, a note of caution. The long-term effects of deliberately inducing genetic manipulations on these growth factors aren’t known. And it hasn’t been used clinically in humans yet. But it has been done in monkeys.

That’s right. We are close to super strong monkeys. Which, in a bit of an aside, I have to admit actually scares me a little bit. That’s because of this thing I’ve had about monkeys since I first saw “The Wonderful Wizard of Oz” when I was 5 years old. It was the scene where the Wicked Witch of the West calls out her flying monkeys (okay, actually called “winged monkeys”). Those creepy monkeys defeated the Winkies, the Great Oz, and kidnapped Dorothy. When those winged primates came spilling over the rooftops to pick up Dorothy I thought it then and I still think it now—monkeys should not fly.

Instead of flight, muscle strength was on order in 2009 when research scientists at the Center for Gene Therapy at Nationwide Children’s Hospital in Ohio and at Ohio State University carried out their work. They used a virus (a viral vector) to insert the human gene for follistatin into knee extensor muscles of macaque monkeys. Remember that follistatin works to block the action of myostatin. To remove the brake on muscle growth, in other words.

This gene insertion permanently modified the muscle properties of the monkeys. The muscle grew about 25% larger and stronger than normal. This kind of experiment had been done before in other animals like mice, but this was the first time it had been successfully shown in non-human primates. It hints at possible application in humans—and beyond—yet to come.

That’s my scientific explanation for Kal-El’s super-strength under our yellow sun. Using comic book willful suspension of disbelief and assuming a similar physiology for Kryptonians and humans, perhaps the radiation from our yellow sun activated some epigenetic mechanism that eventually led to increased follistatin expression in all the muscles in Clark Kent’s body. Voila. Super-strength. Or super-strength light, I guess, since the strength gain isn’t on the order of 100 x or more that we eventually see in Superman.

But it’s a start. And, more importantly, this approach has huge potential to improve muscle mass and function in those with degenerative muscle disorders. Superman would definitely approve.

 

E. Paul Zehr About the Author: E. Paul Zehr is professor, author and martial artist at the University of Victoria. His books “Becoming Batman”, “Inventing Iron Man” and “Project Superhero” use superheroes as metaphors for popularizing science. Visit his website at www.zehr.ca.

The views expressed are those of the author and are not necessarily those of Scientific American.






Comments 6 Comments

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  1. 1. Bionate 3:50 pm 06/14/2013

    just as an aside it is important to remember that the gravitational field of Krypton is supposedly several times greater than that on earth. So presumably his muscles are inherently stronger and more efficient. So if you combine that with a muscle growth regulator that could explain the additional amount of strength. Furthermore, if we were to assume that Superman’s appearance is a result of convergent evolution and his internal biology is significantly different then it might be the case that he has a photosensitive protein similar to melanin in humans which is more sensitive to yellow light this could in turn activate a pathway which Deregulates muscle growth explaining effect of our sun.

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  2. 2. hungry doggy 4:07 pm 06/14/2013

    First of all I feel silly posting this. I’m way too old to be posting about Superman. But having said that…

    What if Krypton was an artificial planet, a shell that was built around a neutron star for the purpose of harvesting energy from the neutron star. The neutron star was in a binary orbit around a small dim red star. The original inhabitants of Krypton were genetically engineered to (somehow! don’t ask me how!) absorb neutrinos from the small red star and convert the energy from the neutrinos into anti-gravitron particles that allowed them to endure the enormous gravity of the neutron star under their feet, and it also threw up a protective anti-radiation shield over their bodies.

    But Krypton exploded when the neutron star at it’s core got out of alignment with the surface layer of the artificial planet and the outer layer crashed into the neutron star.

    When Kal-eL reached earth he was flooded with billions of times more neutrinos coming from earth’s active sun than he had ever been exposed to from Krypton’s small relatively slow burning red sun. His body converted all these extra neutrinos into gravitrons, which allows him to fly or left heavy objects, and super-charged his radiation shield so that it prevents just about anything from penetrating his skin.

    Please don’t snicker. I already feel silly enough posting this.

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  3. 3. Mr. Mxyzptlk III 10:31 pm 06/14/2013

    Bionate makes a salient point. Actually,the explanation of Superman’s powers has changed over the years. Originally, all the inhabitants of Krypton had Superman’s powers–on Krypton. The powers were the product of evolution. But these powers weren’t particularly “super” by later standards. They included “faster than a speeding bullet” and the ability to “leap an eight of a mile”, but not to fly and certainly not the ability to fly to other planets which is why the inhabitants of Krypton could not escape its doom by flying away. As more powers were added to Superman’s repertoire (including the ability to fly) the explanation of Earth’s lesser gravity was devised to account for Superman’s muscular powers while the yellow sun was given as the explanation for his powers of x-ray vision, telescopic vision, super-hearing, etc. His invulnerability was accounted for by his body’s denser molecular structure. Now the yellow sun seems to be used as the explanation for all of his powers.

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  4. 4. Handin23 11:02 pm 06/14/2013

    @Hungry what you are referring to is called a Dyson Sphere. They have actually been postulated as an energy source for advanced civilizations so I could see it being more plausible in reality over the comic book. How often does that happen?

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  5. 5. LunaEros 8:34 am 06/15/2013

    I think you guys have some pretty good ideas.

    Like the molecular density of his body and our sun putting out slightly different radiation than Kryptons which affects his physiology.
    But I think the gravity idea is way off.

    Remember, Kal-El was an infant when he arrived here. Which mean his body developed into an adult in our planets gravity well so the difference in gravity from Krypton to ours should not make a difference.

    Link to this
  6. 6. Wiseguy007 8:26 am 06/16/2013

    While you all postulate on Superman, and the Wizard of Oz “winged” monkeys, I can not help but see a “Planet of the Apes” scenario unfolding here.

    Link to this

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