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It’s been over forty years since genetically modified organisms became a thing, and they’re
still a contentious subject.
And that’s in part because GMOs suffer from a serious image problem.
That’s probably because most of the GMOs we hear about are designed to increase crop
yield and therefore profit for farmers and big biotech corporations.
So consumers are understandably left wondering, “What’s in it for me?”
The answer to that is: potentially a lot, because there are all kinds of GMOs on the
horizon that are designed to save human lives rather than line pockets.
It’s worth remembering that genetic engineering is a tool—and it’s how you use it that counts.
And today, we’re going to talk about 5 cases where genetic modification could be used to
help people directly, from vaccine-delivering fruits to cancer-fighting eggs.
Beta-carotene is one of the main pigments that gives orange and yellow fruits and vegetables
their brilliant colors.
It’s also an important nutrient because it gets converted into vitamin A—an essential
vitamin that your body can’t make on its own.
Cells all over your body need vitamin A, but it’s especially important to your eyes because
it’s used to make one of the light-sensing proteins that allows you to see.
And while a typical Western diet contains enough of the stuff, in some parts of the
world, vitamin A deficiency is a huge problem.
It affects millions of people, especially kids.
So scientists have been trying to find a way to get people more vitamin A for a long time,
and genetic engineering may be a part of the solution.
Golden rice is a genetically-modified rice variety with lots of beta-carotene in its
grains—which is what gives it that characteristic color.
And because of all that beta-carotene, studies suggest just 100 to 150 grams of cooked golden
rice—about a bowlful—can provide a person with roughly half of the recommended daily
amount of vitamin A.
Rice was chosen because it’s a staple in many parts of the world where vitamin A deficiency
is a big problem, like Africa and southeast Asia.
And unmodified rice plants can already synthesise beta-carotene.
The problem is, they only do this in their leaves—two key steps are switched off in the grain.
So the enzymes needed for those steps are added back in by golden rice’s transgenes—the
genes that come from other organisms.
Specifically, the GE plant has a phytoene synthase from maize, and a bacterial phytoene
desaturase from a common soil bacteria.
These are hooked up to a grain-specific promoter—a sequence of DNA that ensures they’re only
expressed in the rice grains.
And they were added to the rice’s genome with the help of a bacterium called Agrobacterium tumefaciens.
It’s a plant pathogen that, in nature, injects parts of its DNA into plant cells to make
the plants produce tumor-like growths that the bacteria feed on.
Scientists in the 1970s were able to figure out exactly what DNA it introduces and what
genes were needed to make that happen.
And that allowed them to transform this pest into a DNA-delivery vector.
Even now, with all kinds of genetic technologies available, it’s one of most common methods
used to modify plants.
And while the process seems pretty straightforward, golden rice has been in development
for nearly two decades.
Part of that has been tweaking the plants to get them to produce enough beta-carotene
while still yielding enough rice for farmers.
And part of it has been fighting the haters—anti-GMO groups have been campaigning against its introduction
from the get-go.
Despite all these challenges, golden rice is pretty close to becoming a reality.
It’s been approved by multiple regulatory agencies around the world, including the US FDA.
And in places like Bangladesh, commercial cultivation could happen in 2019.
Salsa lovers rejoice!
The day is coming when you won’t have to add hot peppers to your favorite spicy condiment.
Scientists are considering developing a tomato variety that contains the same spicy compound
as a jalapeno or habanero.
It’s probably not immediately obvious to you why this would be considered a “health
GMO,” but as it turns out, the compound that makes peppers spicy — called capsaicin
— also has health benefits.
Scientists are especially interested in its anti-tumor and pain-relieving properties.
And that’s where tomatoes come in.
Tomatoes are a distant relative of hot peppers — the two diverged around 19 million years
ago — and they still possess the genes to make capsaicin.
They’re just turned off.
So, to get spicy tomatoes, genetic engineering would just have to coax the plants to turn
them back on.
Scientists could just get capsaicin from hot peppers directly instead of tinkering with
tomato genes.
But, peppers are especially vulnerable to pests, and the amount of capsaicin they produce
is unpredictable.
Also, it takes a lot of land to grow them in bulk.
A hectare will only produce about 3 metric tons of hot peppers, while the same plot of
land can yield around 110 metric tons of tomatoes.
This is all still theoretical, but scientists are considering a couple of approaches to
turn those bland tomatoes into capsaicin factories.
In one approach, scientists could use proteins called transcriptional activator-like effector
proteins, or TAL effectors.
These bind to promoter sequences in plant DNA to turn genes on.
They actually originally come from Xanthomonas species, bacterial plant pathogens which cause
a disease called bacterial spot in tomatoes and peppers using these expression-changing proteins.
But, like the bacteria used to make golden rice, TAL effectors can be customized to activate
pretty much any plant genes scientists want—including the key genes in the capsaicin synthesis pathway.
Alternatively, scientists could use gene editing techniques like CRISPR to replace the promoter
regions of the inactive genes with promoters from genes that are expressed in tomato fruits.
If they used this method, there wouldn’t be any transgenes involved—the plants would
just have sections of their own DNA copied and pasted elsewhere in their genome.
Of course, until researchers actually try these ideas out in a lab, they won’t know
for sure if reactivating the genes will work the way it’s supposed to.
If it does, though, it’ll be great news for health professionals studying capsaicin—and
for pranksters looking for an especially evil practical joke.
One of the most common childhood allergies is milk and dairy.
Kids generally outgrow it, but about two to three percent of infants can’t be given
milk products, including most formulas.
And that’s a difficult problem if they are not or cannot be breastfed.
But geneticists think they have a solution: a genetically modified cow whose milk doesn’t
have the whey protein beta-lactoglobulin, or BLG—the main allergen behind milk allergies.
The first of these hypoallergenic cows was Daisy—a dairy cow in New Zealand whose creation
was detailed in a 2012 study in the journal PNAS.
Added to her genome are two small snippets of DNA that create microRNAs—tiny RNAs that
interfere with protein production.
To make a protein, cells first transcribe the DNA from a gene into RNA, and then that
RNA is translated into a protein sequence.
MicroRNAs bind to these RNA sequences, keeping them from getting translated.
Daisy expresses two microRNAs to target the BLG protein, so she produces basically none
of it in her milk.
Since the 2012 study, scientists have monitored 12 of Daisy’s female offspring, and they
have no detectable levels of BLG in their milk, either—which suggests the change is
lasting, so a herd of hypoallergenic cows is possible.
More recent studies have used other gene editing approaches to simply turn off the BLG gene.
A 2018 paper in the journal Scientific Reports used zinc-finger nucleases, a kind of molecular
scissors, to snip BLG’s promoter region, creating a mutation that makes it inactive.
Both of these are still proof of concept studies, though.
And they’ve run into the same problem.
A cow’s body seems to compensate for the lack of BLG by increasing expression of other
milk proteins, including casein, which can separately trigger allergies.
So more research is needed before GMO cows can actually start providing the world with
allergen-free milk.
Cancers are a major medical problem, and it doesn’t help that the drugs we use to treat
them can be expensive and difficult to produce.
Take interferon-beta, a tumor-suppressor that doctors can prescribe to help tackle several
kinds of cancer.
The protein is produced naturally by the human body to help regulate the immune response.
But since we can’t really extract large amounts of it from people, for pharmaceutical
use, it’s manufactured in what’s called a mechanical bioreactor.
The process involves growing tons cells that have been genetically modified to produce
the drug, then extracting the drug afterwards.
Then one day, some scientists in Japan apparently thought, “You know what’s less expensive
than a mechanical bioreactor?
A chicken.”
As they explain in a 2018 paper in Scientific Reports, the team used CRISPR to insert human
interferon-beta DNA into the chicken’s primordial germ cells—the ones that become sperm.
They stuck the gene next to the one for ovalbumin—the main protein in egg whites—to ensure the
drug would be heavily expressed in eggs.
The modified cells were then injected into two and a half day-old embryonic roosters,
which grew up into healthy adults with the new gene in their genome.
That’s only step 2.
These males were then bred with hens so that they’d end up with offspring that carried
the protein-producing gene.
The hens from that generation were the ones that went on to lay eggs with interferon-beta
in their whites, from which the drug could be extracted.
This seems like an awful lot of trouble, but chicken-produced interferon-beta could be
up to 90 percent more cost-effective than the stuff made with the usual production method.
In fact, these chickens are so efficient at producing the protein that some estimates
say a small flock of a few hundred birds could satisfy worldwide demand for the drug.
And there are other benefits to using chickens, as opposed to plants or other animals.
It turns out chicken proteins and human proteins have similar patterns
of sugar groups added to them.
So human immune systems are less likely to attack proteins produced by chickens than
those made by traditional methods.
And these Japanese drug-making chickens aren’t the only ones out there.
Scientists in the UK have also successfully created GMO chickens that produce cancer-fighting
proteins in their eggs.
But so far, these engineered chickens only show it’s possible.
We’re years away from such research changing the way many drugs are manufactured.
People in places like the US might take for granted the fact that there are no logistical
barriers keeping them from getting vaccinations to prevent some of the world’s worst diseases.
But vaccines generally have to stay refrigerated and be administered by a doctor, and that
means they’re a lot harder to get in some parts of the world.
That’s why scientists are trying to make edible vaccines — plants that are genetically
engineered to provide immunity to the people who consume them.
The idea is that they’d work a lot like a regular vaccine—they’d deliver some
benign target that looks like a key part of the dangerous pathogen, so your immune system
can learn to recognize that and mount an effective defense
if you’re ever exposed to the real deal.
Researchers have already made a banana that contains a chunk of DNA from the bacteria
that causes cholera, for example.
The transgene in the fruit—which encodes for a harmless part of the cholera toxin—was
added using Agrobacterium, in a process much like the one that created golden rice.
And in the end, the bananas contain enough of the protein that one dried banana chip
could be an effective vaccine dose.
Banana-based vaccines are also being developed against hepatitis B, but they’re likely
to work best against gastrointestinal diseases like rotavirus—a highly contagious childhood
stomach ailment that kills more than 200,000 children a year.
That’s because the bananas come into direct contact with the mucosal lining of the stomach,
stimulating the immune defenses there.
You could theoretically choose any edible plant for such vaccines, but bananas are a
pretty great choice because they don’t need to be refrigerated and are already a common
staple in areas where these vaccines are most needed.
And, they’re often eaten raw.
And that’s an important piece of the puzzle, because cooking
could destroy the vaccine part.
Banana-vaccines could also be really cost-efficient.
According to one estimate, about 81 hectares of land could be enough to produce hepatitis
B vaccines for every baby in the world.
But, these edible vaccines aren’t quite ready to hit the world stage—there are some
kinks to work out, like getting them to make reliable amounts of the
inserted protein in each fruit.
Perhaps the biggest hurdle, though, is simply the long path to clinical approval.
Like any other vaccine, GM bananas will have to run the regulatory gauntlet to show they’re
both safe and effective before they’re approved for use, and that could take decades.
There are a lot of other awesome GMOs in the works, too—like carrots with more calcium
to fight osteoporosis.
Or, tobacco plants that produce antibodies which inactivate the ebola virus.
Our ability to manipulate genomes has all sorts of potential medical uses.
Because genetic engineering isn’t an inherently bad thing.
And when it’s used well, it can do a lot of good.
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And if you want to learn more about genetic engineering specifically, you might like our
episode on CRISPR.
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