All About mRNA: The Molecule That Runs the World

Illustration by Virginia Gabrielli for Elemental

I can depend on my body. My muscles contract when I want them to — to carry me up mountains and down ski slopes, to pull my kayak paddle through the water, and move my hands across piano keys. When I drink my favorite red wine, my liver metabolizes the alcohol, and my digestive system handles all the carbonara I throw at it and then asks for more. My brain secretes adrenaline that protects me in dangerous situations and serotonin that reminds me how good it is to be alive.

My muscles, metabolism, and mind do all the things I expect them to, and my body (and yours) is constantly performing a near-limitless number of other functions as well. It’s all thanks to a tiny, immensely powerful molecule you may have heard a lot about recently: mRNA.

Every bodily function, both voluntary and involuntary, seen and unseen, happens because messenger RNA — commonly shortened to mRNA — is at work in our cells.

At the most essential level of cellular function, mRNA is the body’s Rosetta stone.

“It’s involved in every process,” says Rob Swanda, a fifth-year biochemistry PhD candidate at Cornell University. “Cell signaling, the production of hormones and every enzyme in your body—mRNA is just as critical as any other genetic material you have to allow you to be yourself and do what you want to do.”

In December, Swanda went viral on Twitter for his easy-to-digest videos explaining the science behind mRNA-based Covid-19 vaccines being produced by drug companies Pfizer and Moderna.

But long before it was a buzzword and a beacon of hope for the end of a global pandemic, mRNA was quietly going about its job inside every single cell in every living organism.

What does mRNA do exactly, and why is it so important?

To understand that, you first have to understand the role of proteins. Often called the “workhorses” of the cell, proteins carry out most cellular functions. For example, enzymes — which the body uses to build muscle, break down toxins, and metabolize nutrients — are proteins. Many hormones are proteins, and so are the Y-shaped antibodies produced by the immune system.

“Everything is done with proteins,” Swanda says. “Your fingernails growing, your fingerprints, your eye color, the sound of your voice. If you’re in starvation, your body knows to slow down protein production to conserve nutrients and amino acids. And I’m not talking about days — in the hours in between your lunch and dinner, your body knows to shut down and wait till it gets its next meal. It’s so intricate and fine-tuned that it runs like a well-oiled machine.”

In short, your body needs to produce countless types of proteins to do just about everything, and the codes to produce them are contained in DNA.

“In a way, we can produce medicines inside the body.”

Think of a cell’s DNA as a recipe. It’s the instructions required to make the protein that will carry out that cell’s function. Except there’s a small hitch in this particular giddy-up: The recipe is written in a foreign language. Luckily, mRNA is available to translate.

During a process called transcription, mRNA forms a single strand of nucleotides — the molecules that chain together to form RNA and DNA — that matches the nucleotides on one side of a strand of DNA helix. Then, the RNA carries the “message” from the cell’s nucleus into the cytoplasm, where a second process, called translation, uses the mRNA’s now-decoded recipe to build the necessary protein. At the most essential level of cellular function, mRNA is the body’s Rosetta stone.

It’s mRNA that carries the protein production instructions, which makes it an incredibly powerful tool. Scientists have been working since the molecule’s discovery in 1961 to harness that potential and to get the body to make specific proteins by introducing mRNA that’s been produced in a lab and loaded with a custom set of instructions.

“In a way, we can produce medicines inside the body,” says Marta Ortega-Valle, founder of GreenLight, a biotech company that manufactures lab-produced RNA. “We could, instead of manufacturing proteins outside of patients, create them inside the body, using your own cells and the same system your body already has.”

mRNA could end the pandemic and other diseases

The early Covid-19 vaccines represent a major breakthrough in mRNA-based medicine. They work by using custom-programmed mRNA to produce the virus’ unique “spike protein” — the mechanism it uses to attach to healthy cells — inside the body. The immune system recognizes the spike protein as an invader and cooks up targeted antibodies to attack and destroy it. The vaccine mRNA doesn’t last long, and once it degrades, spike protein production stops. But the immune system now has the recipe for that specific antibody in its collection: If the real virus enters the body, it will recognize the spike protein, and the immune response should be swift and effective.

“Your body has years of evolution to do it right,” Ortega-Valle says. “So, what is wonderful about mRNA and that molecule is that we’re using nature to cure you.”

The vaccines may be the first publicly available pharmaceuticals to use mRNA, but they won’t be the last. Not by a long shot. GreenLight is currently working with the Gates Foundation to develop an mRNA-based treatment for sickle cell anemia. Research has been done into the potential for mRNA as an anti-aging therapy. The list of conditions and diseases that could theoretically be treated or prevented using mRNA vaccines and medicines is long.

If we’re approaching an era of mRNA dominance in medicine, it’ll be a supremacy that’s well deserved.

“It’s hard to find where this wouldn’t work,” Swanda says. Many cancers, he adds, arise because of proteins getting the wrong signals from cellular DNA. “Proteins can be turned on or off, which can elicit an uncontrollable amount of cell growth. They get a signal that says, ‘Keep growing, keep dividing!’ Or they don’t get the signal that tells them to slow down. So, can we repair these proteins through mRNA? Can we give them the correct instructions back, to say, no, this is what to do?”

Ortega-Valle and many in the science community believe the next frontier of medicine is based in mRNA. And now we’re expected to get there a lot faster. “I think that we’re experiencing an acceleration that was not in the plan,” she says. “My guess is that without the pandemic, a commercial vaccine based on mRNA would have taken many years, if it ever happened. Now we’ve done it, and it opens the door to more.”

If we’re approaching an era of mRNA dominance in medicine, it’ll be a supremacy that’s well deserved. After all, it makes you, me, and everyone else who we are. So, whether you’ve gotten an mRNA Covid-19 vaccine already or plan to get one, offer a moment of gratitude to the molecule that runs the world.

Kate is a freelance journalist who’s been published by Popular Science, The New York Times, USA Today, and many more. Read more at

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