Translator: Robert Tucker Reviewer: Luca Ballistri
CRISPR-Cas.
What is it?
A potato chip?
No.
CRISPS-Cas is a new technology to modify DNA.
Who has already heard about modification of DNA?
Scientists are rewriting the genome of the fruit fly.
And when it goes well, it's still just a fruit fly.
New genes have been introduced into the soybean.
Corn seed has been modified.
Eh ... right, right! GMOs: genetically modified organisms.
It can already be done, so what are we talking about?
What's new about CRISPR-Cas?
CRISPR-Cas brings with it the promise of a revolution.
A revolution such that CRISPS-Cas was named
innovation of the year 2015. by the scientific journal "Science".
A revolution such that two big American universities
were in bitter legal dispute
until literally two days ago
for the intellectual property rights.
A revolution such that scientists, who are indeed visionaries,
but who are also chronic sceptics by quirk of professional,
have been overwhelmed by a "CRISPR-craze",
a wave of intense enthusiasm.
Wherein lies the greatness of the breakthrough that is CRISPS-Cas?
It is in the fact that it is a technology that is simple, fast and cheap:
the three key elements of a great success.
How does CRISPR-Cas work?
It works a bit like a "cut and stitch" kit
for rewriting DNA.
The main fundamental component is Cas9,
a protein, specifically an enzyme, that cuts the DNA.
Cas9 is, therefore, our "molecular scissors".
These scissors must, however, be brought to the right place to cut on the DNA.
Think that the human genome has 3 billion bases.
That's like saying
that it's an instruction manual with 3 billion characters.
And our molecular scissors, Cas9,
have to find the right piece of DNA among 3 billion characters,
and it does it using a string of just 20 nucleotides,
just 20 characters to find among 3 billion the precise point to cut.
These are numbers that seem important, but I do not know how much they say,
so let's think about an Olympic swimming pool
full of coloured golf balls.
Imagine we want to find the golf ball
of the colour we want among all those in this pool.
Quite a job, right?
Now imagine 1,200 Olympic swimming pools full of coloured balls, all different.
CRISPR-Cas will succeed in the job of finding the coloured ball
of the colour you want.
How does it do it?
And here is the difference with respect to previous technologies.
CRISPR-Cas uses a guide RNA?
What is a guide RNA?
What is an RNA?
RNA is a molecule very similar to DNA
that has the property
of being able to pair with DNA of complementary sequence.
So the guide RNA finds the DNA of complementary sequence,
brings the Cas9 there
and there the cut, the modification, will be made.
This blob is Cas9.
The guide RNA has hooked up the Cas9,
and now appearing in red, the sequence of 20 characters
that will pair with the DNA to be cut.
What happens?
We have our "cut and stitch" kit: Cas9 and guide RNA.
This molecular complex, or "cut and stitch" kit,
scans all along the DNA,
hooks up to the RNA-identified section of the DNA.
You saw that Cas9 unrolls the double helix of the DNA as if it were a zip fastener.
Perfect recognition!
Snip! Snip!
The molecular scissors have cut the double helix of the DNA,
the double strand.
If now we wished to change the sequence of DNA to be cut,
the gene sequence to be modified,
what must we do?
It’s so simple!
We must simply change the sequence of the guide RNA,
the trivialist of operations.
It's simple to design,
and the material required is also very easy to obtain,
to synthesize, to produce in large quantities.
So much so, that a guide RNA costs just a few tens of euros,
inclusive of shipping.
And this is already a godsend for us researchers
because it has shortened experiment time from several months to a few weeks.
So, we've made our cut.
How do we stitch?
There are various mechanisms
that the cell will use to restitch the DNA.
And this part, we, in fact, leave to the cell to do.
The mechanism that interests us most
with regard to clinical applications, that is, to patient therapy,
is a mechanism that we could define as a DNA patch.
This DNA patch can be supplied by us, from the outside.
An alarm is activated because there are these two floating DNA filaments.
It's a very serious thing for the cell.
Panic! Red alert!
The DNA patch arrives that we supply from outside,
which as you see is sticky on the sides,
is complementary to the cut DNA sequence,
but in the middle there is a sequence of DNA that is what we want,
how we want it to be,
designed by us,
For example,
it's a healthy gene sequence
put in the place of a sick gene
that we have cut out with CRISPR-Cas previously.
So, you see what we did?
We have rewritten the DNA in the right place, where we wanted to.
Today,
scientists all over the world
are working feverishly to optimize this system.
They are looking for other CRISPR-Cas systems,
improving on what we already have.
They are trying to make it even more precise,
and even to improve an essential first step.
You will realize
that this modification package
of Cas9 "molecular scissors", guide RNA, and DNA patch,
must enter the cell in some way.
And, well, maybe not in all the cells of the organism,
but only in those of the brain,
only in those of the liver,
only in those of the heart,
or only in sick cells and not in healthy ones.
So, how's it done?
This first step is called delivery.
It is not a problem exclusive to CRISPR-Cas;
it is a step necessary for all types of gene modification.
In fact, delivery is a process that has been studied for decades,
for example for gene therapy.
One of the pioneers of delivery is an Italian, Luigi Naldini, who works at
the San Raffaele Telethon Institute for Gene Therapy in Milan
with his colleagues and students.
What have they done, these scientists?
They have used for the delivery of genetic material in cells
something else
that must be handled with great care.
That is the HIV virus.
What did these scientists do?
They took the HIV virus
and they completely removed from it its pathogenic potential,
its ability to cause the disease.
And what have they done
with this new virus of completely safe design?
They have filled it with genetic material
which serves, for example, to cure hereditary childhood diseases,
obtaining moreover stratospheric success.
And so we can imagine filling this restructured HIV virus,
or some other virus,
with slightly different features,
with our "cut and stitch" package:
Cas9 "molecular scissors",
guide RNA, and DNA "patch".
Package delivered, delivery accepted.
As you see,
CRISPR-Cas gives us enormous power.
The power to change almost any living organism
with applications, as mentioned, of therapeutic nature,
but also in other fields,
for example, in the agro-industrial field.
Virtually anything that we obtain through biotechnology
can be improved through the use of CRISPR-Cas.
For example,
from our yogurt in the morning -
where, among other places, CRISPR-Cas has its origins, was born,
in the dairy industry -
to the vitamins that we take after the yogurt we eat in the morning,
to the production of drugs,
like insulin for people who have diabetes,
or to the production of enzymes to get laundry whiter.
With this enormous power, there comes too though, of course,
enormous responsibilities.
There are anxieties, fears, doubts, concerns,
expressed in public opinion
that are focused mainly on the possibility of modifying embryos.
Why?
Because modifying embryos
modifies not only the individual that will be born of that embryo,
the modification is also transmissible to their offspring.
So you change this individual,
their children, their children's children, their children's, children's children.
We have said that CRISPR-Cas is very precise.
But it is not infallible.
And, therefore, in addition to the mutation
that we have deliberately introduced,
we could end up also introducing other unintentional mutations
without knowing what the long-term effects of these mutations will be
on the health of that individual,
of their children, of their children's children,
of their children's, children's children.
What does that mean?
That we should not modify embryos?
That we should prohibit it a priori?
My opinion is no.
And that's not just my opinion,
but also that of a well-nourished community.
Because, in some cases, CRISPR-Cas,
the modification of the embryos by CRISPR-Cas,
or some other gene editing technique,
is the only possibility.
We must see it as an opportunity that has its risks and its benefits.
And in my opinion, occasionally, it is worth taking a risk
if the benefit is sufficiently great.
Let me, however, dispel a myth.
Eugenics.
What's meant by eugenics?
You'll find it in the newspapers if you haven't already.
It is the possibility of changing
physical characteristics a little superfluously.
I don't know, like: hair, eye or skin colour;
IQ, physical strength.
It's science fiction.
Why?
Firstly, because many genes control each of these characteristics.
And secondly, we don't know which they are currently.
So, today, talking about eugenics is like talking about unicorns.
We can do it for fun,
but maybe we should focus on, and talk about, other things
because there are so many,
and they are more pressing and more realistic.
Of course, in my opinion, this debate should involve all of society.
If you think about it,
each of you finances science through the taxes you pay.
So what science does concerns you as beneficiaries and as mandators.
I want to leave you with one last reflection.
To participate in a mindful and constructive way in a debate,
you need to be informed,
and, in this particular case,
we must know to choose well the sources from which we draw our information.
Scientists, researchers,
are not stars,
alpha females, lone wolves,
hermit preachers, misunderstood geniuses.
No.
So, we have to try to select well those that are our sources of information.
Let's do that.
Otherwise, CRISPR-Cas, it will remain a potato chip.
Thank you.
(Applause)