HomeArticlesWill Gene Editing Lead to Editing Humanity? | Google Zeitgeist
Will Gene Editing Lead to Editing Humanity? | Google Zeitgeist
November 15, 2019
It’s a great pleasure to be here. I speak
to you today as a professor at University of California, Berkeley, although I am a cofounder
of some companies that are using gene editing and, you know, I’ve been struck at this meeting
by the incredible advances being made in information technology, and certainly living in the Bay
Area, we experience that very directly. But I think what’s really interesting to me
is that there’s a parallel explosion going on in biology right now, and that’s really
what I want to talk to you about this morning, a technology that is enabling manipulation
of the information that controls biological systems that, I think you’ll see, very nicely
parallels some of the things that we’ve heard about earlier in the meeting.
So to kick this off, you know, this is really a technology that is about rewriting the language
of life, rewriting the DNA that controls the cells, organisms that we see around us and
that are us, and it really begins with thinking about the way that information is stored in
biological systems. So unlike in computers where we store information
electronically, ones and zeros, in biology information is stored chemically. It’s stored
in the information of DNA. And this is showing you the beautiful structure of DNA, the double
helix that was discovered back in the 1950s. And in, in fact, when I was growing up in
Hawaii, I was growing up in a rural town in Hawaii. Nobody in my family was a scientist.
But the way I got turned on to biology was by reading a book my dad gave me about the
discovery of the structure of DNA, and I was so amazed by the fact that scientists could
do experiments to understand the structure of a molecule, that that’s actually what got
me excited about going into biochemistry and structural biology.
So, you know, when we look at the structure like this, this is basically showing how information
is stored in the form of letters of DNA. You know that — you might know that DNA has four
letters, and the thing that makes it so useful for storing information is that the letters
pair with other letters to form the double helix and that’s how information can be replicated
accurately and stored for future generations. Now, ever since the discovery of the structure
of DNA, scientists have been thinking about how they could manipulate that molecule, how
we could synthesize it, how we could make copies of it, and also how we could change
it. Could you actually alter the information inside of a cell in a way that would allow
manipulation of that information very precisely. It sounds sort of like science fiction.
But the idea really was, could you have — could you really create some kind of an editor for
DNA, sort of analogous to the way that we might have an editor in our — to edit a document
on our computer where we can move text around, we can change it, cut and paste things, correct
a typo. What if you could actually do that in the DNA of a cell? It kind of sounds like
science fiction, right? But scientists have been thinking about this
for the last few decades and sort of chipping away at how to do this, and technologies have
been coming along for making changes precisely to the DNA of cells.
The challenge has been that those technologies have not been widely adopted.
Why not? Because they were hard enough to use and they — there’s sort of a high enough
energy barrier that most scientists like me had looked at those earlier technologies and
said, “Well, that looks really exciting but it looks too hard to use.”
And so the story that I want to tell you today is about a technology for gene editing that
came about from a very unexpected direction. Research that I was doing with my collaborator,
Emmanuelle Charpentier, that was directed in a very different direction, we thought,
than gene editing initially, and it was really about a curiosity-driven project to understand
how bacteria fight viral infection. And it was through the course of that research
that we uncovered a mechanism that cells use to fight viral infection that could actually
be repurposed, we harnessed as a technology for gene editing. And it’s a technology that’s
become known as “CRISPR.” So to explain how this works a little bit,
I want to first show you that, you know, all cells are susceptible to viral infection.
So this is an example of a virus landing on the surface of a bacterial cell, and in this
example — and this actually happens — in bacteria, the DNA of this virus is packaged
inside the head, that sort of round structure in the virus, under very high pressure, and
when the virus lands on the surface of the cell, it’s literally like harpooning the cell,
injecting the DNA into the cell, where that DNA of the virus very rapidly takes over the
machinery of the cell. And this is true for any kind of viral infection
in us or bacteria and other kinds of organisms. In bacteria, when this process begins, the
cell has very little time to defend itself from the virus before it gets killed, so there’s
a really high selective pressure for cells to come up with strategies to defend themselves,
and one of those strategies is a system called CRISPR. It’s an adaptive immune system that
allows cells to recognize this foreign DNA, steal little pieces of it, store it in the
DNA of the cell at a place in the genome called CRISPR, so it keeps a genetic record of viruses
that have infected these cells over time, and then it makes a chemical copy of the DNA
in the form of a related molecule called RNA that provides the cell with a way to program
its immune system to find and destroy viral DNA that has a matching letter sequence.
What does that mean? Well, let me just show you —
[ Laughter ] Let me show you the actual machinery that
does this and then I’m going to show you a little video that illustrates how it works.
Okay. So this is a 3D printed model of the actual molecule that carries out gene editing.
It’s a molecule — it’s a protein called Cas9 shown here in the — it’s the white molecule.
And the great thing about this technology is that this protein, Cas9, can be used for
any experiment of gene editing in any cell, and the reason it can work with any — in
any cell and recognize any sequence of DNA is that it’s programmed with a replaceable
piece of RNA. That’s the orange molecule in this model.
The orange molecule has a series of letters that match the sequence of letters in DNA
that a bacteria might want to find and destroy, if it’s a virus, but as a technologist we
might want to use it to program — to find a certain sequence in the genome of a cell
to make a change. And the way this system works is that the
protein, the white molecule, with its programmable RNA orange molecule, searches through DNA
in the cell, the blue double helix, to find a sequence of letters matching the RNA sequence.
And when that match occurs, this protein grabs onto the DNA at that position and it makes
a very precise cut in the DNA double helix. Now, when that happens in animal and plant
cells, the cell can actually take over, repair the cut, and in the course of repairing the
cut, make a change to the DNA at that position. Okay. So let me show you a video that illustrates
how we imagine that this actually works inside of an animal or a plant cell.
So we’re looking at a cell, and of course in animals and plants the DNA is actually
packaged inside the nucleus of the cell, so we’re zooming in here to the nucleus.
And you’ll see that the blue DNA is wrapped around some green proteins that allow the
DNA to be highly compacted inside the nucleus. Now, the amazing thing about the CRISPR technology
is that this programmable enzyme, Cas9, searches through all of the letters of the DNA in the
nucleus to find a single set of letters — 20 letters — that match the letters in the RNA.
And when that match occurs, the DNA opens up, this protein cuts the DNA, and then it
hands off those broken ends of the DNA to repair enzymes in the cell that can fix the
break. And in this example, we’re seeing actually insertion of a new piece of information at
the site of the break. That’s what makes this very powerful. You can control where changes
occur in the DNA by triggering this repair pathway by introducing a break.
Now, the remarkable thing about this technology is that it works in essentially any kind of
plant or animal or fungal or any other type of organism where it’s been tested, so it’s
very powerful. It’s a democratizing technology because it’s
simple to deploy. Any student — we’ve had high school students come to the lab. They
can take out their iPhone, they can type in a sequence of letters that they want to synthesize
in the form of RNA, they can order it from a company, and within a couple of days they
can be programming this enzyme, Cas9, to make genetic changes to human cells or any other
kind of cells that they are — they’re interested in studying.
So it’s a really remarkable, really powerful technology for doing something that not long
ago seemed like science fiction. So where do we go from here?
I want to point out that — you know, the way that this technology is being deployed
right now. So we’re already seeing multiple clinical trials that have started already
to test this, initially in cancer patients but probably in the not-distant future to
test this system also for treating genetic diseases in mouse models of muscular dystrophy
or HIV/AIDS infection. We’ve already seen efficacy using the CRISPR technology to treat
these animal models of disease. So there’s tremendous excitement about this.
And also, of course, in agriculture, excitement about being able to engineer plants precisely
to allow them to adapt to climate change and other kinds of attacks that are happening,
pathogens that might attack plants. All of these types of changes, at least — certainly
in clinical medicine right now are being done in cells that we call somatic cells. They’re
fully differentiated cells, cells that exist in kids or adults. They’re not cells that
are going to pass changes on to the future — future generations.
But one of the things to appreciate about this technology is because it works in effectively
any cell type, it can also be done — this kind of gene editing can be done in what we
call the germline. And this is an example of germline editing. So what you’re seeing
here is a pipette on the left-hand side that’s holding on to a fertilized egg — this is
actually a fertilized mouse egg — and a needle coming in from the right that’s injecting
the gene editing molecules into this fertilized embryo. And when that animal then develops,
it will have changes that are induced by this — by the injected CRISPR Cas9 molecules.
Those changes will be transmitted to all of the cells of the organism. And not only that,
to their children, children’s children, et cetera.
So these become heritable changes. And it was appreciated early on with this
technology that this works very nicely in mice. It turns out it works in lots of other
kinds of organisms. I wanted to show you one example of sort of
illustrating how simple this is to do and also how beautiful a result one can get with
this kind of germline editing. So this is an experiment that was done by
a first-year graduate at the University of Texas and she was kind enough to share this
with me. Sunada Khadka. And what Sunada did in this experiment is
she took frog embryos. These are two-cell embryos, so they have two cells and the cells
are split right — round embryos, there are two cells on each side of the round embryo.
And she injected the CRISPR molecules into one of the two cells in such a way that she
removed a gene important for making the brown color of these frogs and replaced it with
a gene that makes the frog — makes the cell glow green. And so you see these beautiful
embryos with one cell glowing green, the other cell unedited, and when these animals — these
animals are otherwise completely normal, these are allowed to develop, these are the tadpoles
that develop. And you can see that in the image on the — on your left, these animals
have a split right down the center, with the normal brown color is gone from the cells
on the bottom of the animal and, you see on the right-hand side, replaced by the green
gene. So it’s a very, very interesting, very powerful
technology, and this is something that was done by a first-year graduate student.
So it turns out that this kind of germline editing works in other animals. It also works
in mammals. It works in — in monkeys. And an experiment that was published in early
2014 illustrated this, in which monkeys that were treated in the same way that I just showed
you with the frog embryos were edited in the germline, so that the resulting animals could
pass on those genetic changes to their progeny. And for me, this was kind of the moment when
I realized that as excited as I was about this technology, I started to feel a little
bit nervous because, you know, this technology is powerful enough that it can also allow
changes to be made, heritable changes to be made, in human beings. And this was actually
a cover of “The Economist” from about a year ago under the banner, “Editing Humanity,”
with the article talking about the exciting challenges that we now face where we have
a technology that can allow correction of mutations that would cause disease, but also
potentially introduce changes to human populations that lead to changes in traits that some might
consider enhancements, and should we go there, is this something that should happen.
And just to give you a flavor of how fast the technology is moving, so I — I spoke
about this last year, last summer at Google Camp, and just in that — in that amount of
time, so it’s not quite a year, this technology has now moved to the point where it’s possible
now to make cells from human somatic cells, so fully differentiated cells. It’s now possible
to make eggs and sperm, certainly in mice and probably very soon in human beings that
will obviate the need to do embryo editing. We won’t have to do that. We can edit eggs
and sperm of people and then use those edited germ cells to — for fertilization, if that
were desired. So the pace of the technology is unbelievably
fast, and I think that, you know, it’s really important for scientists and, frankly, all
of us to appreciate the wonderful opportunities it offers but also the real challenges that
we face now with ethical decisions about how to use this technology appropriately.
Thank you very much.