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We have the first published example of using light and gene therapy to restore someone's vision! And in heavier (metal) news, a recent study found surprisingly high levels of mercury in meltwater from the Greenland Ice Sheet.

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This episode is brought to you by Nature’s Fynd.

We teamed up with them to explain the science behind Fy, their nutritional fungi protein. You can check out the link in the description to learn more. [♪ INTRO].

For many of us, the black and white stripes of crosswalks are part of everyday life. Well now, one 58-year-old study participant, who was previously almost totally blind, is rejoining that club. According to a study published this week in Nature Medicine, those crosswalk lines are one of the things he was able to see after a combination of gene therapy and some very fancy goggles gave him back a rudimentary version of sight.

This is a remarkable milestone for patients with a specific form of blindness. The single participant in this case study had been losing his sight for forty years, because of a disease called retinitis pigmentosa. It currently has no approved treatment for most patients and it results in progressive blindness as the light-sensing cells of the retina stop working or die off.

But the researchers saw a potential fix in a technique called optogenetics. That’s a tool that makes nerve cells sensitive to light so they can be cued and controlled. It works thanks to microbes with genes that produce light-sensitive proteins called opsins.

Using a modified virus as a delivery system, we can get the genes that code for microbial opsins into cells of vertebrates like ourselves. Once that’s done, you’ve got a neuron that produces a protein that can translate light into the very kind of electric current that makes said neuron fire. The end product is a neuron that fires when the right light is shined on it.

That has a lot of research applications for studying neural circuits and what different neurons do, we’ve talked about it a lot on SciShow, but scientists haven’t yet found many ways to apply it clinically. In this particular case, though, the researchers injected the viral vector carrying the opsin gene into one of the participant’s eyes, where it made neural cells in the retina called ganglion cells sensitive to light. But that was not the final step in the process.

The light we see varies widely in different environments, and it doesn’t correspond perfectly to the frequency of light that the microbial opsin used in this procedure responds to. Instead, the participant had to learn to use a special pair of goggles, which would translate incoming light into light that could stimulate his genetically modified eye cells. That took a while, because they were essentially reprogramming his brain to know what the heck this weird and foreign information coming from the ganglion cells meant.

But finally, seven months after training started, the patient reported being able to see while wearing the goggles. There was that stripey crosswalk, of course, but in the lab, he could also see notebooks and staple boxes of different shades of gray against a white table. In some tasks, he could also say how many objects were on the table or locate where they were and reach for them -- at least part of the time!

This trial was to establish the safety of the technique, and there’s definitely still more work to be done. Other people have received the gene therapy, but had not completed the training with the goggles at the time this paper was published. They only treated one of the patient’s eyes and didn’t restore his vision fully.

The researchers say that so far, the treatment is low-res enough that it’s only helpful in patients with really advanced disease. But still… kind of amazing. It’s the first published example of using optogenetics to treat someone’s blindness, and the someone in question reports that it’s helped him with activities in his everyday life.

But that’s enough of the light news, let’s get to the heavy stuff. This is a mixed metaphor. It’s the heavy metal stuff.

A study published this week in Nature Geoscience found surprisingly high levels of mercury in meltwater from the Greenland Ice Sheet. Mercury is worth worrying about because it is toxic, and organisms can’t really get rid of it once it’s in their bodies. That means it accumulates in higher and more toxic levels as you move up the food chain.

And in Greenland, which depends on exporting fish like cod and halibut to the rest of the world, increasing mercury levels could have both health and economic impacts. That said, mercury in the Arctic is not a new concern. Concentrations of mercury have increased tenfold in aquatic life up there in the last century and a half, and high concentrations of mercury have been found in Arctic rivers.

But until now, no one had really looked at the Greenland Ice Sheet. The ice sheet is a big deal because it is very, very big: it’s the second largest body of ice on the planet, and it’s melting fast. And the study results were surprising.

The researchers found that meltwater coming off the glacier contained levels of mercury that were around ten to a hundred times higher than those in Arctic rivers. In fact, they were some of the highest mercury levels recorded in natural water anywhere on Earth. The levels were pretty comparable to what’s been found in contaminated and urban areas.

And when researchers looked farther downstream at the fjords fed by the glacial meltwater, they found that those had high levels of mercury too. We don’t know where all this mercury came from, but the researchers think it likely originated from bedrock erosion or geothermal activity under the glacier, since the concentration in the meltwater is higher than that in the snow on the glacier’s surface. They also noticed that microorganisms living below the glacier had adaptations that suggested they were used to living with high mercury concentrations.

While it’s nice to hear that they don’t think this extra mercury is all related to human activity, they do say that an unexpected natural source of mercury might actually be harder to deal with. We often think of the world’s glaciers as huge frozen hunks of water. And while we know that they’re melting and that that melting is not great, this is a whole other level of complication that we don’t normally think about.

Because glaciers aren’t just huge frozen hunks of water. They’ve also got other stuff in them. It’s gonna help us navigate our warming planet if we have secure sources of protein.

And that is where Nature’s Fynd comes in. They’re working on bringing a microbe with origins in Yellowstone National park all the way to your table, via their breakthrough fermentation process that produces high-protein food. Their nutritional protein, Fy, is meatless, dairy-free, and delicious.

I had some of their cream cheese, and it was very good. I also had one of their sausage patties, and it was very good. If you want to learn more about Nature’s Fynd and the science behind their meatless and dairy-free foods, check out the link in the description. [♪ OUTRO].