Proteins.
They’re a major part of our everyday diet - they’re in chicken, eggs and my favourite
- cottage cheese.
Proteins are needed to make your muscles move, to make your nerves fire, they’re pretty
much involved in almost everything that your body does.
So surely something that is a major chunk of our food intake, and a big deal in the
makeup of our bodies, couldn’t hurt us could they?
Well, yeah.
There is a protein that could kill you.
And it’s called a prion.
All proteins are made from long chains of building blocks - amino acids - that are intricately
folded up into specific three dimensional shapes.
The shape determines a protein’s function, so if the shape changes, the protein doesn’t
work.
A prion, it turns out, is a normal protein that has somehow been folded up wrongly, like
tangled up headphones in your pocket – and we all know how frustrating that can be.
But the real problem comes when the misfolded prion comes into contact with other proteins.
Just like putting a neat set of headphones in with your tangled set, you know its going
to end up in one huge mess.
The misfolded prion protein acts as a template to tell its neighbours to also twist and contort
incorrectly.
Each of those then changes its neighbour, and it starts an exponential cascade of pathologic
proportions.
Without the right shape, the proteins in the brain can’t do their job properly, and the
brain itself grinds to an erratic, but inevitable halt.
But where do these chaos-causing proteins come from?
For that, we need to turn to two very different groups of people - the cannibalistic Fore
tribe of Papua New Guinea, and the family of an 18th Century Venetian doctor.
Both the Fore and the Venetians were once medical mysteries, thanks to the strange and
terrible diseases that afflicted them.
At first glance, the symptoms were very very different.
Many of the members of the Venetian family were completely unable to sleep, for months
at a time, until they died of apparent exhaustion and organ failure.
Their affliction became known as Fatal Familial Insomnia.
Whereas, on the other side of the world, the Papua New Guineans were struck with uncontrollable
shaking and laughter along with mental decline.
Their disease was named Kuru, which means ‘to shake’, or alternatively named the
macabre ‘Laughing Disease’.
Despite their differences though, autopsies of both groups revealed that all of their
brains were full of tiny holes, where normal grey and white matter should have been.
Both groups had forms of what’s known now as TSE – transmissible spongiform encephalopathy.
A human version of mad cow disease in cattle and Scrapie in sheep.
Other symptoms of TSE included difficulty speaking, unsteadiness when walking, and severe
mental deterioration over a couple of months before, invariably, death.
It was vicious and unstoppable, and for a long time, medical professionals had no idea
what caused it.
Most infectious diseases are caused by pathogenic agents like bacteria, viruses, parasites.
But the sufferers of TSE seemed to have no such infection.
What could be so powerful to cause a brain to so suddenly and irreversibly begin to eat
itself?
Theories were thrown around, but for many years there was simply no proof.
It wasn’t until the 1980s that an American scientist, Stanley B. Prusiner, managed to
find and isolate the cause of TSE.
And you’ve guessed it, it was the prion.
One of the things that makes prions so terrifying, is that there’s more than one way they can
get into your brain.
Like many normal pathogens, they are infectious, meaning that if you come into contact with
affected tissues, the prions can make the leap to you.
That’s what happened to the Fore tribe.
As a mark of love and respect to their dead, their funeral rites involved extracting and
eating the brains of the deceased.
Once one person died of Kuru, this morbid tradition led to countless more being infected.
Thankfully though, once it was found that literally eating brains was the cause of the
brain-eating disease, the Fore people found other ways to honour their dead, and the Laughing
Disease is all but gone from Papua New Guinea.
However, the Venetians aren’t known for eating brains, so they must have contracted
their prion disease in another way.
As well as being infectious, prions are also hereditary, meaning that the instructions
for them can be carried in a family’s genes and passed on to future generations.
And so, thanks to a potently tangled protein, fatal familial insomnia has been killing members
of the same Italian family for over 250 years.
And sadly, it continues to do so today, because there is no known cure for prion diseases
- the proteins themselves are ridiculously difficult to destroy.
And they can lay dormant for decades before triggering the disease, and they can even
be transmitted from animals to humans.
In the UK 150 people have died from TSE to date, although several thousand are thought
to be infected with dormant prions.
It’s genuinely scary stuff.
But while we wait for science to fill the gaps in our knowledge about these deadly proteins,
the Fore tribe can give us at least one ray of hope.
A simple lesson, and one that I feel we should all try to live by.
Don’t, if you can manage it, eat other people’s brains…
If this wasn’t all too gruesome for you, give us a like and check out our other videos
here at BBC Earth Lab.
Click to subscribe and be notified of new videos, and remember kids, don’t eat brains.
If you remember one thing today, its that.