Good evening.
Here you see a little petri dish that we use in the lab
with a dry leaf, completely dry,
and on there, there are females.
Why do I say females?
Because that's their way of life: They live and evolve without males;
they got rid of males.
And also, they are dry.
They can dry up, and we can wait for years,
put them in the freezer, and get them back.
Tonight we will do a live experiment with one of my scientists, Boris,
to resurrect these animals for you,
these females.
Thanks, Boris.
So look around you.
There is an amazing diversity of living organisms on this planet,
from bacteria to fungi to plants to animals to human -
nothing looks alike.
But do you know that all this diversity arose once from a universal ancestor
around 3.5 billion years ago?
And this ancestor of all living organisms was a single simple cell,
something like a bacterium.
But how do we know that all life has evolved from a single cell?
We know this because we all share the same alphabet;
we have the same DNA code.
DNA is a magical molecule of life.
And DNA is only made up of four chemical building blocks:
cytosine, guanine, adenine, thymine.
So only four letters that make the whole alphabet of life.
So yes, from bacteria to human, we only need four letters,
but then, what's our DNA instruction book looking like?
In each of our cells, we have around three billion of those letters,
organized on 23 pairs of chromosomes.
So you see here,
it's a compaction of these four letters.
But what makes you different from me is that these letters change.
These letters change between all these individuals.
So if we all have the same genetic code, it means we are all related.
Yes, we are.
We are all cousins from each other.
But then, you may wonder:
How did we evolve to so many complex forms
from such a single cell a long time ago?
And that's when I want you to remember the card game we have been playing.
What's essential for evolution is genetic variation,
its changes in these letters.
So these letters change randomly.
And most of these changes are neutral,
they have no effect on the fitness of the individual,
but if a change is an advantage, it can be selected.
Remember?
We select if a positive mutation appears.
Why is it selected?
Because the individual gets an advantage
and it might reproduce more than the others
so the mutation is transmitted.
And we know
that natural selection is cumulative,
that we can accumulate this positive mutation,
which is important for adaptation and evolution.
So as I said, during the card game,
there is nothing of intelligence or a creator out there
for evolution.
And look at cancer development.
Cancer development is also an evolutionary process;
it follows this same mechanism.
Each of our cells accumulate randomly these changes, these mutations,
but if one of these normal cells suddenly gets a growth advantage -
a mutation that gives it a growth advantage compared to the other cells -
it will start to grow quicker -
an uncontrolled proliferation -
and cancer can occur.
And of course, it's a problem to human.
We know it.
But you know, animals also get cancer.
But do all of them get cancer?
There are a few mysterious species that don't develop cancer.
What are they?
The most notorious one is this naked mole rat.
Very cute animal, no?
(Laughter)
For scientists, it's a very interesting animal.
It's very small. It's like a mouse.
But it lives for 30 years, and a mouse lives for four years.
What's also interesting is
if you inject the cancer cell in this animal,
it will not develop.
And why?
Scientists have searched for this for years
and found that they have this kind of molecule -
a high molecular mass, hyaluronan;
it's a kind of super sugar -
that is secreted around the cells of these animals,
and it makes their tissue very elastic.
And why is it important?
Because these animals dig into the soil, they make these burrows,
and so their tissue needs to be very elastic.
So it's an adaptation to this.
But what's interesting
is that this molecule, when it's secreted around the cell,
prevents the cell from dividing or proliferating further.
So you immediately see
the interesting application of the discovery of such a molecule.
But if you think this is the only interesting animal out there,
you’re wrong.
Nature is full of mysterious species, where we can discover so much.
Nature has been an inspiration to scientists for so many years.
Like Albert Einstein said,
"We know less than one thousandth of 1% of what nature has to reveal to us."
And if we start to destroy our nature,
we will not even discover everything that's out there.
Look at this gecko.
This gecko, we know, can run quickly on vertical glass.
But how?
How can these animals adhere so strongly to glass
and then just run on it?
And so, for long,
scientists looked at the molecule:
What kind of molecule is secreted that makes them like a glue,
like a strong adhesion?
And in fact, by looking at these fingers,
they found there's nothing of a molecule that is secreted,
but it's a structure.
What they discovered
is that underneath these fingers, there are these hair-like structures,
millions of them.
And if you look even at the nanoscopic level,
you see that at the end of all of these hairs,
you have hundreds of these spatula-likes structures.
And when these are in strong contact with glass,
it creates a strong adhesion just through simple Van der Waals forces,
the simple forces that make this strong adhesion.
And when they rotate their fingers,
this force releases immediately and they can run further.
And of course,
laboratories have now been interested to reconstruct these nano-structures
to make strong adhesives.
And that's what I want to show you:
It's so interesting to study biology because there's so much to discover,
because there has been such a long evolution
of all kinds of specimens with all kinds of different adaptations.
And what has puzzled me is reproduction.
You know that for life, it's essential to reproduce;
we need to reproduce or the species will go extinct.
But do you know that sexual reproduction,
the one we all know,
is the queen of problems in evolutionary biology?
For us scientists, it's really a puzzle.
And why?
Think about all the energy you need to spend to find a partner,
all the strategies the male's developed
to try to attract a female, to try to fertilize her,
to the point that there is a battle of sexes.
Believe me -
a man penis is boring compared to this insect penis.
This is a penis of a bean weevil,
full of spines,
and the males with the longest spines are those that fertilize most of the eggs.
Of course, the female cannot reproduce anymore afterwards,
but at least, the male is sure he has transmitted his genes.
A look at this fruit fly.
You might have many fruit flies in summer around your trash bin.
This fruit fly, Drosophila bifurca,
produces giant sperm, 20 times its body size.
It's like, you men,
you would have a sperm that is twenty times your body size,
like a building of 12 stories.
(Laughter)
Wow!
But at least, when it transmits this to the female,
the receptacle of the female is filled,
there is no space for another sperm,
so it's sure to transmit its genes.
But then, why did such a complicated mode of reproduction evolve?
And why is it so omnipresent?
Is it not just simpler to clone yourself?
One individual makes a new individual?
So why is sexual reproduction so prevalent in nature?
In fact, for us biologists,
sex is just about mixing genetic material of one individual with another individual
to create each generation of offsprings that are all different.
And that's a force of sexual reproduction:
It creates every generation this genetic variability
that is essential for evolution.
So does it mean that animals that lose sexual reproduction
or that abandon it or have no sexual reproduction
cannot evolve, cannot adapt?
That's what we thought
until we discovered
what has been called an evolutionary scandal
or an ancient sexual scandal:
It's a microscopic world of animals, the bdelloid rotifers.
These are females cloning themselves; never has any male been discovered.
They exist since millions of years and we found them everywhere.
And they are not only interesting
because they can reproduce without males and evolve without males,
we can also dry them out.
I showed you:
We can just take them, here in the park,
a piece of lichen, a dry lichen, bring it back to the lab,
and what you see -
that's also what you see on the microscope -
is this dry lichen and then they are in trance.
But when we add water, they start to live again.
So these animals -
We can dry them out at any stage in their life,
and we can keep them dry.
We can put them in the -80 freezer.
We can send them to collaborators in the US,
and if they add water, they live again.
And it's not only one species.
You could think, "Yeah, but it's just this rare animal."
No, it's more than 400 species being described
as having diversified into many morphological forms -
all females reproducing without males,
most of them being able to dry out.
And of course this makes the newspaper:
["Asexual reproduction is possible."]
Yes, it's possible.
But then, of course, you might think, "How did these females evolve?"
How do they create variability? -
because we know it's essential for evolution.
So, if they just cloned themselves, how do they ever evolve and adapt?
And so, as a scientist,
it is important to have these hypothesis to think of.
So our hypothesis is -
It's easy to work with this animal.
You take a female in the wild, you start to clone it in the lab,
you have millions of identical females,
we dry them up,
and then, our question was,
"Do these females -
What happens to the genetic material of these females
when we dry them up?"
We know from bacteria
that drying up breaks their genetic material into pieces.
Is this also happening in these animals?
And then, what if they don't repair perfectly these pieces,
is this a way to create variability? -
meaning,
if you replace males by drying up, you might also evolve.
And so, that's what we tested.
So Boris has designed a very nice protocol in the lab
to dry them up with a high survival rate.
And what happened to these females when they are dried up?
You see, the longer they are dried up, the more their DNA is broken.
The simpler the gel and the DNA migrates through it,
the smaller the pieces.
And when we hydrate them, what you see is that they start to repair.
So they can come out of drying, they have their broken DNA -
but they can survive with broken DNA apparently -
and then they start to repair.
And you know,
if you have a cancer cell,
it's known that sometimes during a division some DNA breaks,
and it repairs this broken DNA but not perfectly,
and you can have an aggressive cancer that appears.
What they do in proton therapy is
use proton radiation to completely destroy the DNA of cancer cells
so the cells get completely broken DNA, and molecules too.
So we thought if we do proton radiation to these animals,
what happens?
So we took, again, a female,
we dry it up,
we add proton radiation,
and what happens?
DNA gets completely broken.
And this 800 grays of proton radiation are huge doses.
There are no living cells that can survive this.
But what's amazing here is -
you really see the DNA is completely broken -
when we re-hydrate these females, 99% of them survive.
So they come out of drying with a completely broken DNA,
without a problem,
and then they start to repair.
And of course, the question is,
"Do they really repair perfectly?
Or do they put all the pieces of DNA back together
into their 12 chromosomes? -
because we found they had 12 chromosomes -
or is that just creating some variability?"
So we have here preliminary results that I'm just showing you tonight,
where we did this experiments,
where we dry them up,
we irradiate them,
and then we look at its genomic structure.
Not going too much into detail,
but what you see here is, for example,
pieces of the ridge of the genome from a female
before she was radiated or dried up.
Then we dry it up, we irradiate it,
and we look at whether these pieces come back.
You see here - everything is destroyed, and whether we get these pieces back -
showing it's stitching back all these DNA pieces together
into these 12 chromosomes.
So they can do this:
They reconstruct their genome as before,
or at least, that's what it seems to look like.
And even the descendants have that same structure
as a parent’s alignment.
So is there no genetic scrambling going on?
That's possible.
Maybe they don't, indeed, make a completely new genome;
they keep their genome.
But what we then ask ourselves is:
"How can you survive when you are irradiated,
because not only your DNA is broken, but also your molecules must be broken?"
But they must keep their molecules somehow intact
because you need these molecules to repair your DNA.
So what do they have?
What's their secret?
What did we find by sequencing the first genome,
really sequencing the entire alphabet of this animal?
We found that they have a huge amount of antioxidants.
Antioxidants are essential
to protect yourself from these damaged cells.
We all have antioxidants.
That's because our cells accumulate damages,
a kind of what we call oxidative stress,
and your proteins, your DNA - everything gets damages.
That's why we get older.
And that's why you put all these creams on that are full of antioxidants,
to try to prevent the aging of your cells,
but it will not.
But here, these animals have a huge amount of these antioxidants.
So next time, think about it,
don't buy all these expensive creams full of antioxidants,
just drink some rotifers.
You find them in the nature and they might help.
(Laughter)
But of course,
these are all things we discovered,
but as a scientist,
when you discover things, you have even more questions.
And so recently,
I obtained a grant from the European Research Council
to really try to demystify all these mysteries we found.
We found they have this huge amount of antioxidants,
but are they really effective?
How do they repair this broken genome?
What are the molecules, the mechanism they have
to repair such a broken genome to survive drying, freezing?
Then one last thing we discovered is
by sequencing their genome, we found, among their genetic material,
genetic material from bacteria, plants, fungi -
so they seem to integrate DNA from their environment.
And that's of course puzzling.
But we also thought,
If they can integrate this foreign DNA,
can they also integrate DNA from other females out there,
other rotifers that also dry up?
And the first results we got on this
is that we found some signatures of DNA exchange between these females,
and we think it's not conventional sex, because we never found males,
so they are not using the strategy that all animals do -
a sperm and an ovocyte to exchange DNA.
So what is the strategy? We have no idea.
We call it sapphomixis -
it's a mixing of genetic material between females.
And you immediately see here why it's so beautiful to be a scientist -
you discover a lot, but you have even more questions.
But what's for sure
is that we have a very interesting model organism here to understand,
"How can they evolve without males?
How does sapphomixis happen?
And how can they survive such extreme conditions
as drying up, freezing, and high doses of radiation?"
There's so much still to discover there.
And one of our next challenges is to send them to space.
We got a grant from the European Space Agency
to send, in 2019, rotifers to space, RISE.
Why? Because space is also an extreme environment.
We have no idea at the moment
what this extreme environment has
as pressure on astronauts or any living animal.
This is a very interesting model organism to send out there
and to understand much better what space is like.
And of course,
I cannot end this presentation without thanking all the funding
but especially all the people in my lab - many are here.
This work is never done by one person.
A lab is really a group of persons working,
tackling these questions.
A lot of frustrations.
They know it better than me right now.
And then, I would like to thank the rotifer and Boris
with the whole experiment
because thanks to these rotifers,
I'm really happy to go every day, or almost every day, to my work.
At least, when I know I can do science and I can work with rotifers,
I'm a happy person.
Thank you.
(Applause)