Gene editing can now change an entire species -- forever
-
0:01 - 0:03So this is a talk about gene drives,
-
0:03 - 0:06but I'm going to start
by telling you a brief story. -
0:07 - 0:1020 years ago, a biologist
named Anthony James -
0:10 - 0:12got obsessed with the idea
of making mosquitos -
0:12 - 0:15that didn't transmit malaria.
-
0:16 - 0:20It was a great idea,
and pretty much a complete failure. -
0:21 - 0:23For one thing, it turned out
to be really hard -
0:23 - 0:25to make a malaria-resistant mosquito.
-
0:26 - 0:30James managed it, finally,
just a few years ago, -
0:30 - 0:32by adding some genes
that make it impossible -
0:32 - 0:35for the malaria parasite
to survive inside the mosquito. -
0:36 - 0:37But that just created another problem.
-
0:38 - 0:41Now that you've got
a malaria-resistant mosquito, -
0:41 - 0:44how do you get it to replace
all the malaria-carrying mosquitos? -
0:46 - 0:48There are a couple options,
-
0:48 - 0:50but plan A was basically to breed up
-
0:50 - 0:53a bunch of the new
genetically-engineered mosquitos -
0:53 - 0:54release them into the wild
-
0:54 - 0:56and hope that they pass on their genes.
-
0:57 - 0:59The problem was that you'd have to release
-
0:59 - 1:03literally 10 times the number
of native mosquitos to work. -
1:03 - 1:05So in a village with 10,000 mosquitos,
-
1:05 - 1:07you release an extra 100,000.
-
1:08 - 1:09As you might guess,
-
1:09 - 1:12this was not a very popular strategy
with the villagers. -
1:12 - 1:13(Laughter)
-
1:15 - 1:19Then, last January,
Anthony James got an email -
1:19 - 1:21from a biologist named Ethan Bier.
-
1:21 - 1:24Bier said that he
and his grad student Valentino Gantz -
1:24 - 1:27had stumbled on a tool
that could not only guarantee -
1:27 - 1:30that a particular genetic trait
would be inherited, -
1:30 - 1:32but that it would spread
incredibly quickly. -
1:33 - 1:35If they were right,
it would basically solve the problem -
1:35 - 1:38that he and James had been
working on for 20 years. -
1:38 - 1:43As a test, they engineered two mosquitos
to carry the anti-malaria gene -
1:43 - 1:45and also this new tool, a gene drive,
-
1:45 - 1:47which I'll explain in a minute.
-
1:48 - 1:50Finally, they set it up
so that any mosquitos -
1:50 - 1:52that had inherited the anti-malaria gene
-
1:52 - 1:56wouldn't have the usual white eyes,
but would instead have red eyes. -
1:57 - 1:59That was pretty much just for convenience
-
1:59 - 2:01so they could tell just at a glance
which was which. -
2:02 - 2:05So they took their two
anti-malarial, red-eyed mosquitos -
2:05 - 2:08and put them in a box
with 30 ordinary white-eyed ones, -
2:08 - 2:09and let them breed.
-
2:09 - 2:13In two generations, those had produced
3,800 grandchildren. -
2:14 - 2:16That is not the surprising part.
-
2:17 - 2:19This is the surprising part:
-
2:19 - 2:22given that you started
with just two red-eyed mosquitos -
2:22 - 2:23and 30 white-eyed ones,
-
2:23 - 2:26you expect mostly white-eyed descendants.
-
2:27 - 2:30Instead, when James opened the box,
-
2:30 - 2:33all 3,800 mosquitos had red eyes.
-
2:33 - 2:35When I asked Ethan Bier about this moment,
-
2:35 - 2:39he became so excited that he was literally
shouting into the phone. -
2:40 - 2:42That's because getting
only red-eyed mosquitos -
2:42 - 2:45violates a rule that is the absolute
cornerstone of biology, -
2:45 - 2:46Mendelian genetics.
-
2:47 - 2:48I'll keep this quick,
-
2:48 - 2:51but Mendelian genetics
says when a male and a female mate, -
2:51 - 2:54their baby inherits half
of its DNA from each parent. -
2:54 - 2:57So if our original mosquito was aa
and our new mosquito is aB, -
2:57 - 2:59where B is the anti-malarial gene,
-
2:59 - 3:01the babies should come out
in four permutations: -
3:01 - 3:04aa, aB, aa, Ba.
-
3:05 - 3:07Instead, with the new gene drive,
-
3:07 - 3:09they all came out aB.
-
3:10 - 3:12Biologically, that shouldn't
even be possible. -
3:12 - 3:14So what happened?
-
3:15 - 3:16The first thing that happened
-
3:16 - 3:19was the arrival of a gene-editing tool
known as CRISPR in 2012. -
3:21 - 3:23Many of you have probably
heard about CRISPR, -
3:23 - 3:26so I'll just say briefly that CRISPR
is a tool that allows researchers -
3:26 - 3:29to edit genes very precisely,
easily and quickly. -
3:30 - 3:33It does this by harnessing a mechanism
that already existed in bacteria. -
3:33 - 3:36Basically, there's a protein
that acts like a scissors -
3:36 - 3:37and cuts the DNA,
-
3:37 - 3:40and there's an RNA molecule
that directs the scissors -
3:40 - 3:41to any point on the genome you want.
-
3:41 - 3:44The result is basically
a word processor for genes. -
3:44 - 3:47You can take an entire gene
out, put one in, -
3:47 - 3:49or even edit just a single
letter within a gene. -
3:50 - 3:52And you can do it in nearly any species.
-
3:53 - 3:57OK, remember how I said that gene drives
originally had two problems? -
3:58 - 4:01The first was that it was hard
to engineer a mosquito -
4:01 - 4:02to be malaria-resistant.
-
4:02 - 4:05That's basically gone now,
thanks to CRISPR. -
4:05 - 4:07But the other problem was logistical.
-
4:07 - 4:09How do you get your trait to spread?
-
4:10 - 4:12This is where it gets clever.
-
4:13 - 4:17A couple years ago, a biologist
at Harvard named Kevin Esvelt -
4:17 - 4:18wondered what would happen
-
4:18 - 4:22if you made it so that
CRISPR inserted not only your new gene -
4:22 - 4:24but also the machinery
that does the cutting and pasting. -
4:25 - 4:29In other words, what if CRISPR
also copied and pasted itself. -
4:30 - 4:33You'd end up with a perpetual
motion machine for gene editing. -
4:34 - 4:36And that's exactly what happened.
-
4:37 - 4:40This CRISPR gene drive that Esvelt created
-
4:40 - 4:44not only guarantees
that a trait will get passed on, -
4:44 - 4:46but if it's used in the germline cells,
-
4:46 - 4:49it will automatically copy and paste
your new gene -
4:49 - 4:51into both chromosomes
of every single individual. -
4:52 - 4:54It's like a global search and replace,
-
4:54 - 4:57or in science terms, it makes
a heterozygous trait homozygous. -
4:59 - 5:02So, what does this mean?
-
5:02 - 5:04For one thing, it means we have
a very powerful, -
5:04 - 5:07but also somewhat alarming new tool.
-
5:09 - 5:11Up until now, the fact that gene drives
didn't work very well -
5:11 - 5:13was actually kind of a relief.
-
5:13 - 5:16Normally when we mess around
with an organism's genes, -
5:16 - 5:18we make that thing
less evolutionarily fit. -
5:19 - 5:21So biologists can make
all the mutant fruit flies they want -
5:21 - 5:23without worrying about it.
-
5:23 - 5:26If some escape, natural selection
just takes care of them. -
5:27 - 5:30What's remarkable and powerful
and frightening about gene drives -
5:30 - 5:32is that that will no longer be true.
-
5:33 - 5:37Assuming that your trait does not have
a big evolutionary handicap, -
5:37 - 5:39like a mosquito that can't fly,
-
5:39 - 5:42the CRISPR-based gene drive
will spread the change relentlessly -
5:42 - 5:45until it is in every single individual
in the population. -
5:47 - 5:50Now, it isn't easy to make
a gene drive that works that well, -
5:50 - 5:52but James and Esvelt think that we can.
-
5:53 - 5:57The good news is that this opens
the door to some remarkable things. -
5:57 - 5:59If you put an anti-malarial gene drive
-
5:59 - 6:01in just 1 percent of Anopheles mosquitoes,
-
6:01 - 6:03the species that transmits malaria,
-
6:03 - 6:08researchers estimate that it would spread
to the entire population in a year. -
6:08 - 6:11So in a year, you could virtually
eliminate malaria. -
6:11 - 6:15In practice, we're still a few years out
from being able to do that, -
6:15 - 6:18but still, a 1,000 children
a day die of malaria. -
6:18 - 6:20In a year, that number
could be almost zero. -
6:21 - 6:24The same goes for dengue fever,
chikungunya, yellow fever. -
6:25 - 6:27And it gets better.
-
6:27 - 6:30Say you want to get rid
of an invasive species, -
6:30 - 6:32like get Asian carp
out of the Great Lakes. -
6:32 - 6:34All you have to do is release a gene drive
-
6:34 - 6:37that makes the fish produce
only male offspring. -
6:37 - 6:42In a few generations,
there'll be no females left, no more carp. -
6:42 - 6:45In theory, this means we could restore
hundreds of native species -
6:45 - 6:46that have been pushed to the brink.
-
6:47 - 6:51OK, that's the good news,
-
6:51 - 6:52this is the bad news.
-
6:53 - 6:55Gene drives are so effective
-
6:55 - 6:59that even an accidental release
could change an entire species, -
6:59 - 7:00and often very quickly.
-
7:01 - 7:03Anthony James took good precautions.
-
7:03 - 7:05He bred his mosquitos
in a bio-containment lab -
7:06 - 7:08and he also used a species
that's not native to the US -
7:08 - 7:10so that even if some did escape,
-
7:10 - 7:13they'd just die off, there'd be nothing
for them to mate with. -
7:13 - 7:17But it's also true that if a dozen
Asian carp with the all-male gene drive -
7:17 - 7:21accidentally got carried
from the Great Lakes back to Asia, -
7:21 - 7:24they could potentially wipe out
the native Asian carp population. -
7:26 - 7:29And that's not so unlikely,
given how connected our world is. -
7:29 - 7:31In fact, it's why we have
an invasive species problem. -
7:32 - 7:33And that's fish.
-
7:33 - 7:36Things like mosquitos and fruit flies,
-
7:36 - 7:38there's literally no way to contain them.
-
7:38 - 7:40They cross borders
and oceans all the time. -
7:42 - 7:44OK, the other piece of bad news
-
7:44 - 7:46is that a gene drive
might not stay confined -
7:46 - 7:48to what we call the target species.
-
7:49 - 7:50That's because of gene flow,
-
7:50 - 7:53which is a fancy way of saying
that neighboring species -
7:53 - 7:54sometimes interbreed.
-
7:54 - 7:57If that happens, it's possible
a gene drive could cross over, -
7:57 - 8:00like Asian carp could infect
some other kind of carp. -
8:00 - 8:03That's not so bad if your drive
just promotes a trait, like eye color. -
8:03 - 8:06In fact, there's a decent
chance that we'll see -
8:06 - 8:08a wave of very weird fruit flies
in the near future. -
8:09 - 8:11But it could be a disaster
-
8:11 - 8:14if your drive is deigned
to eliminate the species entirely. -
8:14 - 8:18The last worrisome thing
is that the technology to do this, -
8:18 - 8:22to genetically engineer an organism
and include a gene drive, -
8:22 - 8:25is something that basically any lab
in the world can do. -
8:25 - 8:26An undergraduate can do it.
-
8:27 - 8:30A talented high schooler
with some equipment can do it. -
8:33 - 8:35Now, I'm guessing
that this sounds terrifying. -
8:35 - 8:38(Laughter)
-
8:38 - 8:40Interestingly though,
nearly every scientist I talk to -
8:40 - 8:44seemed to think that gene drives were not
actually that frightening or dangerous. -
8:44 - 8:47Partly because they believe
that scientists will be -
8:47 - 8:49very cautious and responsible
about using them. -
8:49 - 8:50(Laughter)
-
8:50 - 8:52So far, that's been true.
-
8:52 - 8:55But gene drives also have
some actual limitations. -
8:55 - 8:58So for one thing, they work
only in sexually reproducing species. -
8:59 - 9:02So thank goodness, they can't be used
to engineer viruses or bacteria. -
9:02 - 9:05Also, the trait spreads
only with each successive generation. -
9:05 - 9:07So changing or eliminating a population
-
9:07 - 9:11is practical only if that species
has a fast reproductive cycle, -
9:11 - 9:14like insects or maybe
small vertebrates like mice or fish. -
9:14 - 9:17In elephants or people,
it would take centuries -
9:17 - 9:19for a trait to spread
widely enough to matter. -
9:20 - 9:25Also, even with CRISPR, it's not that easy
to engineer a truly devastating trait. -
9:26 - 9:28Say you wanted to make a fruit fly
-
9:28 - 9:30that feeds on ordinary fruit
instead of rotting fruit, -
9:30 - 9:33with the aim of sabotaging
American agriculture. -
9:33 - 9:35First, you'd have to figure out
-
9:35 - 9:37which genes control
what the fly wants to eat, -
9:37 - 9:40which is already a very long
and complicated project. -
9:40 - 9:44Then you'd have to alter those genes
to change the fly's behavior -
9:44 - 9:45to whatever you'd want it to be,
-
9:45 - 9:48which is an even longer
and more complicated project. -
9:48 - 9:50And it might not even work,
-
9:50 - 9:52because the genes
that control behavior are complex. -
9:52 - 9:54So if you're a terrorist
and have to choose -
9:54 - 9:56between starting a grueling
basic research program -
9:56 - 10:00that will require years of meticulous
lab work and still might not pan out, -
10:00 - 10:01or just blowing stuff up?
-
10:01 - 10:03You'll probably choose the later.
-
10:03 - 10:06This is especially true
because at least in theory, -
10:06 - 10:09it should be pretty easy
to build what's called a reversal drive. -
10:09 - 10:13That's one that basically overwrites
the change made by the first gene drive. -
10:13 - 10:15So if you don't like
the effects of a change, -
10:15 - 10:18you can just release a second drive
that will cancel it out, -
10:18 - 10:19at least in theory.
-
10:21 - 10:23OK, so where does this leave us?
-
10:25 - 10:28We now have the ability
to change entire species at will. -
10:29 - 10:30Should we?
-
10:31 - 10:32Are we gods now?
-
10:34 - 10:35I'm not sure I'd say that.
-
10:36 - 10:37But I would say this:
-
10:38 - 10:40first, some very smart people
-
10:40 - 10:43are even now debating
how to regulate gene drives. -
10:44 - 10:46At the same time,
some other very smart people -
10:46 - 10:48are working hard to create safeguards,
-
10:48 - 10:52like gene drives that self-regulate
or peter out after a few generations. -
10:53 - 10:54That's great.
-
10:54 - 10:57But this technology still requires
a conversation. -
10:58 - 11:00And given the nature of gene drives,
-
11:00 - 11:02that conversation has to be global.
-
11:02 - 11:05What if Kenya wants to use a drive
but Tanzania doesn't? -
11:05 - 11:09Who decides whether to release
a gene drive that can fly? -
11:11 - 11:13I don't have the answer to that question.
-
11:14 - 11:16All we can do going forward, I think,
-
11:16 - 11:18is talk honestly
about the risks and benefits -
11:19 - 11:21and take responsibility for our choices.
-
11:22 - 11:26By that I mean, not just the choice
to use a gene drive, -
11:26 - 11:28but also the choice not to use one.
-
11:29 - 11:32Humans have a tendency to assume
that the safest option -
11:32 - 11:34is to preserve the status quo.
-
11:35 - 11:36But that's not always the case.
-
11:38 - 11:41Gene drives have risks,
and those need to be discussed, -
11:41 - 11:44but malaria exists now
and kills 1,000 people a day. -
11:45 - 11:49To combat it, we spray pesticides
that do grave damage to other species, -
11:49 - 11:50including amphibians and birds.
-
11:52 - 11:55So when you hear about gene drives
in the coming months, -
11:55 - 11:57and trust me, you will
be hearing about them, -
11:57 - 11:58remember that.
-
11:58 - 12:00It can be frightening to act,
-
12:00 - 12:03but sometimes, not acting is worse.
-
12:05 - 12:13(Applause)
- Title:
- Gene editing can now change an entire species -- forever
- Speaker:
- Jennifer Kahn
- Description:
-
CRISPR gene drives allow scientists to change sequences of DNA and guarantee that the resulting edited genetic trait is inherited by future generations, opening up the possibility of altering entire species forever. More than anything, this technology has led to questions: How will this new power affect humanity? What are we going to use it to change? Are we gods now? Join journalist Jennifer Kahn as she ponders these questions and shares a potentially powerful application of gene drives: the development of disease-resistant mosquitoes that could knock out malaria and Zika.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 12:25
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene approved English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever | ||
Brian Greene edited English subtitles for Gene editing can now change an entire species -- forever |