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There are genetic mutations in the population today that can grant people some seemingly superhuman abilities.
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Sources:
MSTN - stronger muscles
https://blogs.scientificamerican.com/guest-blog/the-man-of-steel-myostatin-and-super-strength/
http://www.nejm.org/doi/full/10.1056/NEJMoa040933#t=article
https://ghr.nlm.nih.gov/gene/MSTN#normalfunction
https://www.ncbi.nlm.nih.gov/books/NBK1498/
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-82502012000300003
http://onlinelibrary.wiley.com/store/10.1113/expphysiol.2012.065243/asset/eph1073.pdf?v=1&t=j1mbvm9e&s=cc218db59ef9337ad4c1baecfb2b099fc4bef4ed
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1698719/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3177043/

ACTN3 - fast-twitch muscles
https://www.ncbi.nlm.nih.gov/pubmed/17289854
https://www.ncbi.nlm.nih.gov/gene/89
https://www.ncbi.nlm.nih.gov/pubmed/26429734/
https://www.ncbi.nlm.nih.gov/pubmed/26148057
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150594
https://www.wired.com/2008/11/the-actn3-sports-gene-test-what-can-it-really-tell-you/
http://muscle.ucsd.edu/musintro/fiber.shtml
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1180686/
http://jap.physiology.org/content/116/9/1197

LRP5 - stronger bones
https://ghr.nlm.nih.gov/gene/LRP5#conditions
http://www.nejm.org/doi/full/10.1056/NEJMoa013444#t=article
http://www.sciencedirect.com/science/article/pii/S0002929707605941
http://www.sciencedirect.com/science/article/pii/S8756328205000165
http://onlinelibrary.wiley.com/doi/10.1359/jbmr.2003.18.6.960/full
https://www.snpedia.com/index.php/Rs1815739
http://www.jbc.org/content/281/50/38276
http://oregonstate.edu/dept/biochem/hhmi/hhmiclasses/biochem/lectnoteskga/jan29.html http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0063323
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Images:
https://commons.wikimedia.org/wiki/File:MyostatinMutantWhippet.jpg
https://commons.wikimedia.org/wiki/File:Protein_ACTN3_PDB_1tjt.png
https://commons.wikimedia.org/wiki/File:General_pathology;_from_the_11th_rev._German_ed._(1921)_(14578295997).jpg
Who hasn’t dreamed of having superpowers?

There’s probably some part of you that wishes a radioactive spider or a chemical dump could give you some epic origin story. But it turns out, there really are somewhat-superpowered people who walk among us, thanks to different mutations in their DNA.

Since your DNA controls everything about you, from what you look like to how your body works, small changes in it can lead to really big changes in things like strength and speed! Take your muscles. There are lots of different molecules that affect how muscle tissue grows, including your skeletal muscles—the ones you use when you move, and also look super great.

One of these molecules is a protein called myostatin, and it’s put together from the instructions in a gene known as MSTN. Normally, myostatin binds to certain receptors on your skeletal muscle cells, which activates signaling pathways that limit how much they grow and divide. But researchers have found at least one mutation in the MSTN gene that creates what’s known as a loss of function.

It changes the instructions enough that the gene stops making myostatin molecules— or at least, stops making proteins that work. Without myostatin, your muscle cells grow bigger and divide way more than usual, which means a huge boost in muscle mass and sometimes more strength. And that leads to a condition called myostatin-related muscle hypertrophy, where people—even children— can look like extra-ripped bodybuilders, but without doing any of the extra heavy-duty workouts.

And the condition doesn’t seem to cause any health problems. So scientists are researching myostatin-related therapies to treat people who have muscle weakness or whose muscle cells die too quickly. Now, huge muscles are one common superhero trait, but what about bursts of power and speed like the Flash?

Well, turns out there’s a mutation for that too. There’s a protein in skeletal muscles called alpha-actinin-3, which is encoded by the ACTN3 gene. And it seems to be involved with fast-twitch muscle fibers.

Fast-twitch fibers are basically what they sound like: they’re muscle cells that have quick contraction times and give you bursts of force. They’re the muscle cells that let you sprint really fast. And fast-twitch fibers are usually full of proteins that break down the long, sugar-storing molecule called glycogen, turning it into glucose and other energy-packed compounds that your muscles need to work.

Now, researchers aren’t entirely sure what alpha-actinin-3 does. But they think the protein could help with a number of things, like making or stabilizing fast-twitch fibers or breaking down glycogen. So, if everyone has this gene, why can’t we all sprint like Usain Bolt?

Well, lots of people have a loss-of-function mutation in the ACTN3 gene, so they don’t have working alpha-actinin-3 proteins. But it’s been found that some top-notch sprinters and weightlifters have at least one functional copy of this gene, which means they can make the proteins that might help with seemingly-superhuman bursts of power and speed. But if endurance is what you’re after, there are some genetic conditions that can increase the strength of your bones.

Kind of like Wolverine’s skeleton… minus the adamantium. There’s a gene called LRP5, which holds instructions for a protein with a mouthful of a name: low density lipoprotein receptor-related protein 5. Because it’s a receptor-related protein, it’s found in lots of your cell membranes, and it’s involved with chemical signaling between cells.

We know that LRP5 is part of what’s known as the Wnt pathway, a signaling pathway that affects lots of important cell processes, including cell development. And some people have a gain-of-function mutation in LRP5, meaning that the altered gene causes its protein to have a whole new function. It seems this mutation can kick-start certain signaling pathways on your bone cells, making them grow denser and bulkier— conditions that are generally called osteosclerosis and hyperostosis.

Some people with these conditions don’t have any health problems. In fact, having extra-dense bones might mean they don’t have to worry about breaking an arm or fracturing their skull as much as the rest of us do. But in other cases, this kind of mutation can cause too much hyperostosis, which can lead to really severe forms of bone growth, like where your skull puts pressure on your brain, or your bones pinch your nerves.

In any case, researchers want to study LRP5 to better understand how genetics can play a role in bone growth, like to understand what causes or can treat osteoporosis. So next time you’re daydreaming about superpowers while reading some X-Men comics, keep in mind that we are all mutants in some way. It’s just that some of our mutations only affect our hair color or our tolerance for milk, instead of giving us huge, awesome muscles.

This episode is brought to you by 23andMe, a personal genetic analysis company created to help people understand their DNA. The name ‘23andMe’ comes from the fact that human DNA is organized into 23 pairs of chromosomes. Through genetic analysis, 23andMe users can see which regions around the world their ancestors came from, and learn how their DNA influences facial features and hair, and sense of taste and smell, and sleep quality, and more.

Just a few weeks ago, I sent in my saliva for analysis. Now that I have the results back, I have learned about my health, my ancestry, and my personal traits. I've discovered that I'm 62% English Irish, but for some reason, 90% of my X Chromosome is French German!

That's weird! Also, my close DNA Relatives are 65% less likely to have skydived, which I do not find surprising. And I have 275 Neanderthal variants, which is less than most Europeans so, basically, I am a below average Neanderthal.

That's just a tiny glimpse, the whole report was so much fun to go through and I feel bad I didn't get one for my wife too, so we could go through it together. I can also learn about my predispositions to different diseases, or choose to keep that information hidden if I would rather not know. I can even get in touch with 23AndMe users who share my ancestry.

If you want to do the same—and also support SciShow— it's super fun, and you can check out 23andMe.com/SciShow.