I’m getting older, which would be fine if it weren’t for the fact that everything
hurts and suddenly I need to nap all the time.
Why body, why?
Hi everyone, Julian here for DNews.
You may have heard the myth that the human body essentially replaces itself every 7 years.
While that’s not strictly correct, I think I see the kernel of truth at the heart of
this myth: most of your body’s cells replace themselves over time.
According to the Science Museum in London - in the time it takes to say this sentence,
50 million of my roughly 75 trillion cells will have died and been replaced.
They do it at different rates though, with skin cells dying off after two or three weeks
while white blood cells can live for an entire year.
So if most of you is hitting the refresh button all the time, why do our bodies still deteriorate?
Scientists from the Salk Institute and the Chinese Academy of Sciences think they’re
onto an answer.
They were looking into the underlying causes of Werner Syndrome, which causes premature
aging and a whole host of disorders normally associated with people much older.
About 1 in 20,000 people in the U.S. have it, and they are prone to early onset of cataracts,
osteoporosis, and some cancers.
Many of them die in their 40s or early 50s.
Werner syndrome is associated with a mutation in the WRN gene.
For most people, the gene codes an enzyme that keeps DNA structured soundly.
But with the mutation, the WRN protein isn’t made properly and it affects the way the DNA
bundles itself.
We’re all familiar with the double helix shape of DNA, but there’s more to it than
that.
If you were to stretch out the DNA from just one cell, it would be about 2 meters long.
To be able to cram all this into just the nucleus, DNA is packaged into chromatins.
Euchromatin is looser, it looks like beads on a string, and this shape makes it easy
for enzymes to access and code more proteins.
Heterochromatin is more tightly bunched and folded, which means the genes tucked in there
aren’t being expressed.
That’s why the vast majority of your cells have nearly identical DNA but they do very
different jobs.
Heterochromatin is folded differently from one type of cell to another, and the way it’s
bunched determines what genes are switched off.
This way the cell saves energy and only does the job it’s specified for.
The researchers mimicked Werner syndrome by deleting the WRN gene in healthy stem cells
and letting the DNA carry on as usual.
Without the WRN protein to interact with the markers on the heterochromatin called epigenetic
tags, the scientists found the heterochromatin started bunching differently and the cells
aged faster.
This could be expanded beyond just people with Werner syndrome: it’s possible the
heterochromatin shapes change over our lifetimes after being wound into chromosomes and replicated
and divided over and over.
Maybe this is what makes our DNA express itself differently and causes our slow decline into
brittle old meat sacks.
And if that’s the case, maybe it’s possible to stop or even reverse the aging process,
provided we can also solve a few other problems father time throws at your DNA like your telomeres
shortening.
Telomeres are long tags at the end of chromosomes that don’t actually code any proteins.
They give the machinery that copies DNA a foothold but they get a little shorter with
every replication.
When they’re finally too short, the cell can’t divide anymore.
There is an enzyme called a telomerase that adds to the ends of your chromosomes, but
over your lifetime they can’t keep up.
There are a couple other factors in aging too, like oxidative stress, which is when
free radicals damage DNA; and glycation, which is when glucose binds to DNA, proteins, or
lipids and gums up the works.
So if we sort out these other issues our DNA has to cope with as time passes, maybe it’s
possible for me to be this young and beautiful forever.
Ok, at least I’ll be young.
So what is it that’s responsible for this mug of mine?
Turns out it might be junk DNA.
Anthony explains how DNA shaped your face too in this video.
Werner syndrome sounds like a seriously raw deal but maybe with gene therapy one day it’ll
be a thing of the past.
Are there any other bizarre afflictions you’d like us to cover?
Let us know in the comments, subscribe if you haven’t already, and I’ll see you
next time on DNews.