eye-color is just around the corner.

But this seemingly miraculous gene-editing technology may not actually be as simple--or

as safe--as we thought.

Just so we're all on the same page, CRISPR (or more accurately CRISPR-cas9) works by

cutting the DNA of a cell at a designated spot, say a section of DNA that represents

a certain gene.

Then, when the cell tries to repair the damaged DNA, it often ends up just disabling the gene

altogether.

This has all kinds of uses.

Maybe we want to turn off a gene that produces too much of a certain protein?

CRISPR can do that.

Say we want to see what a certain gene even does?

CRISPR can help us do that too.

Ever since it was first used to edit living cells in 2013, CRISPR has been touted as a

promising technology for treating inherited disorders, cancer, and other diseases with

no current treatment options.

Teams of researchers around the globe had even hoped to begin human trials in 2018.

But none of those trials have taken place yet, with the exception of China, where researchers

have been working with CRISPR in humans since 2016--no results from these trials have been

published so far.

And in the US, the FDA just placed a 'clinical hold' on the first proposed CRISPR gene

editing human trial.

But why?

Several new studies released in the last few months suggest we need to be more cautious

when editing the human genome.

Two of these studies found that when CRISPR performs its hallmark trick and cuts DNA,

that damage can kill the cell, or make it stop growing.

CRISPR modifications are also less likely to kill cells that have a defective version

of a gene called p53.

P53 plays a role in preventing the onset of cancer by regulating a cell's life cycle,

so by leaving more of the defective cells alive than healthy ones*, CRISPR may be inadvertently

raising the risk of cancer in that patient.

Which is, like, the opposite of the goal.

And we haven't even gotten to the most recent study that raises concerns.

Up until now, CRISPR-cas9's cutting function has been accurate in the specific area of

interest--the spot in the DNA that's supposed to be cut.

But that's because researchers were only looking for mutations caused by CRISPR in

the immediate vicinity of the cut.

New research reveals that in about 20% of cells, CRISPR results in MUCH larger deletions

than we thought**-- up to more than 100 base pairs.

Researchers didn't notice this before because they were looking for harmful mutations and

didn't see any...but that's because the entire region was gone.

In CRISPR treatments that would target billions of cells inside the human body, this could

lead to, again...a risk of cancer.

Putting us right back at square one.

So the human trials have been delayed...where do we go from here?

CRISPR permanently alters your genome, so we want to make sure we get it right before

we make moves in real human bodies.

Well, science marches on.

New and improved versions of this kind of technology are already racing forward, like

a genetic editing tool called REPAIR, which uses a different cutting enzyme--Cas13.

REPAIR works with RNA, instead of DNA, to make temporary or reversible changes.

There's also a newly engineered protein that can alter individual base pairs rather

than a whole chunk of DNA, acting more like surgical forceps than a pair of kitchen scissors.

So continued progress and exciting breakthroughs in this field are still happening--we're

not at the end of our CRISPR rope yet.

It's just that we need to take a step back from the hype and carefully analyze what's

really going to be safe as we move forward.

To stay current with all the CRISPR news that's sure to be plentiful in the coming years,

subscribe to Seeker, and for more on how your body, specifically your immune system, interacts

with the technology, check out this video from Julian.

And, fun fact, CRISPR doesn't just present possibilities in human biology--it could be

used to produce genetically crops too.

I'm Maren, thanks for watching Seeker.