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So maybe you've heard of this thing called CRISPR
that scientists are using to edit genomes and change DNA.
Well, today, we're going to talk about what it is,
and how people are using it, and then do our very own CRISPR
experiment.
Ready?
Let's start by going over the basics of the CRISPR system.
Every living thing contains DNA, and the genes that help
make up that DNA are the instructions our bodies need
to make proteins.
Scientists studying DNA in bacteria
noticed chunks of DNA that repeated themselves
over and over in a row.
They named these regions CRISPR regions
for clustered regularly interspersed
short palindromic repeats.
And in between those repeats were spaces of different DNA
that they called spacers.
Turns out those spacers were DNA sequences
from previous invading viruses saved
by the cells as tiny wanted posters
so that the next time the virus showed up,
the cell would recognize it, and know
to chop up the invading DNA.
The CRISPR regions were acting like an immune system
for the cell, fighting off attackers.
And how would the cell chop up invading DNA?
With the help of DNA cutting Cas proteins, short for CRISPR
associated proteins, and RNA, a molecule
that can carry DNA messages throughout the cell.
The cells transcribed spacer sequences
into short pieces of RNA, which guided Cas proteins
to matching targets.
So when a returning virus invaded a cell,
the matching RNA would guide a Cas protein to its DNA,
and chop it up.
Scientists observed the system in bacteria,
and decided to turn it into a tool for precisely cutting DNA.
By engineering their own RNA guides for the Cas protein,
scientists could selectively target and cut
any position in the DNA.
And soon, scientists were modifying the system
so that they could not just cut the DNA, but also make changes.
When a gene is cut, the cell will try to repair it.
Sometimes it does a good job, and other times, it
makes small mistakes, inserting or deleting
extra small DNA sequences.
These mistakes could alter the gene's protein product,
leaving it broken, or marking it for destruction.
But if the researchers added a new DNA template when they cut,
they could also encourage the cell
to insert the new sequence, adding new genes
or making intended changes.
Scientists continue to look for new cast proteins
and to modify the ones they are already working with
to turn genes on or off in all kinds of different systems
from bacteria, to fish, to human cells.
This lets them ask lots of questions
about how genes and proteins work, and what jobs they do.
And now it's time to try a CRISPR experiment
for ourselves.
Here I've got some yeast.
My friends at the Stanford at The Tech program
have already placed DNA into this yeast
that will code for both a Cas protein and a guide RNA.
The guide RNA is designed to target
a gene that helps to process a certain molecule in the cell.
If the gene is broken, the molecule
will build up and turn red, causing the yeast to turn red.
In these yeast, the CRISPR system
is attached to a kind of switch that
can be turned on by adding a molecule called galactose,
or gal.
Now, to show this in action, we'll
split our yeast into two tubes.
In one tube, we'll add gal to turn the CRISPR system on
and cut the gene.
Hopefully, this will create red yeast.
In the other tube, we'll leave the CRISPR system off.
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So as you can see, in the yeast where we didn't turn CRISPR on,
all the colonies are white.
But in the yeast where we did, we
have a mixture of red and white colonies.
So CRISPR cut and disabled the gene in those red ones.
So now that we know the basics of how CRISPR works,
let's talk to some other grad students
on campus to see how they're using CRISPR to ask questions
in their research.
So I study how CRISPR systems allow
bacteria to defend themselves against nasty things
like viruses.
The way a CRISPR system learns how to fight off a virus,
let's say, is to steal a little piece of information
from the virus, and then store it in a safe place.
And people thought that this stealing of information
only happened from DNA.
And what we've done is we've found a CRISPR system,
and potentially a whole class of them,
where that information can be stolen out of RNA molecules.
So that expands the range of things
that this system might be able to defend the bacteria.
I use CRISPR to study genetic cardiovascular diseases, so
diseases of the heart.
I study a disease called hypertrophic cardiomyopathy,
which is a really long word that basically just means
that a part of your heart is larger than it should be.
And you would think that a big change like this
might be caused by something that's
gone terribly wrong in the genome,
but it's actually usually just really tiny little changes
in the DNA, one little letter.
And so what I do is I grow heart cells in a dish,
and I actually use CRISPR to go in and make
those tiny little changes.
And then I look to see how those change the cells,
and therefore, how they cause the disease.
I use CRISPR to study fat metabolism.
So when you eat butter or oils, you
metabolize that into energy.
And some people don't have the ability to do that.
So we want to know what's going on when you don't
have the ability to do that.
So I'm using CRISPR in flies to create a fly model
organism of the human disease where you can't metabolize fat.
I use CRISPR to study proteins that read marks on DNA.
So I'm using a dead version of the Cas9 enzyme that
does not cut.
This dCas9 is fused to a protein that will serve as a road block
to see what happens if we block the action of those reader
proteins at a specific genomic location.
I use CRISPR to study limb regeneration.
Because I'm interested in limp regeneration,
we specifically use organisms that
are able to regenerate full tissues and full limbs.
And so the organism that I'm concerned with is the tadpole.
And tadpoles are awesome because you can chop off their tail,
and then within a week, they actually regrow a full tail.
And you can't actually tell the difference
between a tadpole that's been injured versus a tadpole that's
recovered.
And so what we use CRISPR for is to study
key genes or key factors that we think
are playing a huge role in regeneration.
We are not knocking out a gene.
We're just blocking its activity for a couple of hours.
And that's unique in the CRISPR system that I'm working with,
but a lot of people are applying these methods as well.
Is that unique in the CRISPR system
you're working with because you made that CRISPR system?
I did make that CRISPR system.
Yeah, yeah.
So that's another advantage of CRISPR
is that it offers people an opportunity to play around
with the original system.
What's so cool about CRISPR and molecular biology in general
is that you have the ability to manipulate something the way
you would just manipulate dough as if you were kneading it,
but it's actually the code of life, of every living thing.
So that's pretty cool.
I think the coolest part of working on CRISPR
is just how quickly things change in this field.
I mean, there were a lot of people
all across the world who were studying these things,
and we didn't really know why studying them was important.
And all of a sudden, it becomes this absolutely world
transforming discovery.
And the people just carried on doing what they do best, right?
I've been to so many conferences with them.
These are the nicest, most diligent, hardworking people
that you'll ever meet.
And they're so helpful.
And every month, there's a new discovery
that I get to open up on my computer and read.
And it's just so exciting, because in any other field,
I guess things might take so much longer to move forward.
But because there's so much interest around this field
right now, it's just really exciting.
So now we know what CRISPR is, how it works,
how scientists are using it, and what
it's like to do a CRISPR experiment in the lab.
So next time you hear the word CRISPR,
you'll be able to jump in with all the knowledge.
This video would not have been possible
without the help and support of so many different people.
First and foremost, the Google Making & Science team
and their #ScienceGoals campaign.
Without them, absolutely none of this would have happened.
Also, my friends at the Stanford at The Tech program--
Barry, and Lauren, and Kevin, and Justin,
who both made and then shared this yeast with me
so that I could show this experiment to you.
Huge, huge thanks to them.
Also the graduate students who let me sit down with them
and pepper them with all kinds of science questions,
so many of which I did not get to share in this video,
but will be coming at you soon.
So huge, huge thank you's to everybody involved,
and also to you guys for watching and sharing.
It means so much to me when you share my videos
with other people.
It makes me feel like maybe I'm doing a little something right
here.
Go forth and do science.
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Are you're not going to ask me what CRISPR stands for?
Because I came up with the best acronym.
Oh, wait, yeah.
Tell me, tell me, tell me.
OK.
I anticipated you were going to ask me, like, what does CRISPR
stand for?
And nobody would be able to answer it.
I looked it up, so I'm cheating.
But instead, my original answer was clearly really important--
what was it?
Clearly Really Important Stuff People Research.
Clearly Really Important Stuff People Research,
which is a much better acronym than clustered-- what is it?
Clustered Regularly Interspa-- all of those words
mean the same thing.
clearly Really Important Stuff People Research.
That is the thing.
[CHUCKLES] You can enjoy that.
Oh, you make me so happy.