Chlamydomonas

They walked into the Nobel Prize ceremony.

No, so first of all, Peter Hegemann, a neuroscientist, was trying to figure out how a single-celled algae species called Chlamydomonas could move towards a light source as quickly as it does.

So this is...

A single-celled algae, and when you shine a light on it, it moves towards the light, which is pretty useful for an algae.

[laughs]

But essentially they looked at this organism called Chlamydomonas, which is a green algae, so a single-celled organism.

And one of the many exciting things it does is it moves towards light, and they wanted to know, well, how is this organism doing this? What they found out was that it uses specialized ion channels, which are those, uh, channelrhodopsins.

Now, ion challenge- ion channels are found in all or most cells, and they es- essentially function to allow ions, things like sodium, calcium, into cells for a variety of different reasons.

And so he wanted to see if he could find that protein in this algae.

The algae is Chlamydomonas.

And he, fortunately, a team in Japan had already mapped the genome of this algae.

So he wrote to them, got the, the genome, it was, you know, all, a list of all the genes, and found two proteins that had the properties he was looking for, um, which he named channel, channel rhodopsin one and channel rhodopsin two.

Picture someone who has been in darkness years, seeing a cup on a table and reaching for it, all thanks to an alga's light sensor.

That sensor is channelrhodopsin, a protein from the single-cell Chlamydomonas that swims toward light via an eyespot.

The alga lacks eyes, yet its eyespot triggers an electrical impulse half a millisecond after light hits it.

Channelrhodopsin 2 opens its pore in only zero point two milliseconds, letting positive ions flow and fire a signal.

We'll walk through five stops on the journey from a pond-dwelling alga to a Nobel Prize-winning tool and now a sight-restoring gene therapy.

First stop: the algal origin.

We'll see how Chlamydomonas uses its eyespot like a microscopic rudder, turning light into an electrical twitch in half a millisecond, a speed that makes the protein feel like a biological flash switch.

Second stop: from algae to neurons.

Announcements will follow in the coming days on this year's Nobel Physics, Chemistry, Literature, Peace, and Economics prizes.

The breakthrough began in nine- the nineteen nineties when Hegemon investigated how the alga Chlo- Chlamy- Chlamydomonas reacts to light in half a millisecond.

He hypothesized that a single protein both captured the light and act as an ion channel.

Nagel tested this hypothesis by injecting Chlamy- Chlamydomonas genes into a fro- into frog eggs, discovering channel rhodopsin two, a light-sensitive ion channel.

In twenty oh three, Nagel and Hegemon published findings that this program could be introduced into human and hamster cells to generate electrical impulses using light.

At Stanford University, Disterhoft demonstrated the technique in rat nerve cells two years later, and the method was named optogenetics in twenty oh six.

Together, they gave biology a light switch, a protein that opens the moment light hits it.

Chlamydomonas swims toward light.

Nagel and Hageman found its sensor, channelrhodopsin.

Blue light opens the channel, ions rush in, and the cell gets an electrical signal.

That's what we'd

like.

So let's consider the unicellular green algae Chlamydomonas reinhardti.

I always have a hard time with these taxonomical names.