Marine biologists discover 4 new types of photoreceptor

How do these little beasties detect light anyway?

Marine biologists discover 4 new types of photoreceptor
Credit: dnz/Adobe Stock
  • The ocean is full of simple single-celled organisms that somehow follow day-night cycles.
  • Researchers have just discovered four new groups of photoreceptors that help the organisms detect light.
  • The photoreceptors may find use in studies of the human brain.

    • When it comes to senses like ours, tiny single-celled organisms floating in the ocean don't have much going on. And yet, as Sacha Coesel, the lead author of a new study from University of Washington researchers, puts it: "If you look in the ocean environment, all these different organisms have this day-night cycle. They are very in tune with each other, even as they get moved around. How do they know when it's day? How do they know when it's night?"

      The answer, according to Coesel and her colleagues, is four previously unknown groups of photoreceptors that may help these organisms detect day, night, and each other.

      Light and dark are vital to these organisms. When the sun is up, they become energized and grow. Cell division occurs at night when the darkness' ultraviolet wavelengths are less damaging to their DNA.

      "Daylight is important for ocean organisms," says senior author Virginia Armbrust, "we know that, we take it for granted. But to see the rhythm of genetic activity during these four days, and the beautiful synchronicity, you realize just how powerful light is."

      Photoreceptors and optogenetics

      Credit: ktsdesign/Adobe Stock

      Aside from being fascinating in their own right, these little "light switches" are likely to be of great interest to people working in optogenetics, a transformative area of scientific research.

      This combination of optical technologies and genetics is giving researchers new insights into the workings of the brain, allowing them to, for example, turn on and off single neurons as they explore the brain's myriad pathways and interactions. Optogenetics also holds promise for better management of pain, and has cast new light on brain motor decision-making.

      These new-found, naturally occurring photoreceptors may substitute for, or complement, human-made photoreceptors currently used in optogenetics. It's hoped that these newcomers will prove more sensitive and better equipped to respond to particular light wavelengths. Possibly because water filters out red light—the reason the ocean looks blue—the new photoreceptors are sensitive to blue and green wavelengths of light.

      "This work dramatically expanded the number of photoreceptors — the different kinds of those on-off switches — that we know of," offers Armbrust.

      Finding the new photoreceptors

      Credit: Dror Shitrit/Simons Collaboration on Ocean Processes and Ecology/University of Washington

      The researchers identified the previously undiscovered groups of photoreceptors by analyzing RNA they'd filtered from seawater samples taken far from shore. The samples were collected every four hours over the course of four days from the Northern Pacific Ocean near Hawaii. One set of samples was collected from currents running about 15 meters beneath the surface. A second set sampled deeper down, gathering water from between 120 and 150 meters, in the "twilight zone" where organisms get by with little sunlight.

      Filtering the samples produced protists—single-celled organisms with a nucleus—measuring from 200 nanometers to one tenth of a millimeter across. Among these were light-activated algae as well as simple plankton that derive their energy from the organisms they consume.

      Under-appreciated, tiny drivers of sea health

      The new photoreceptors help fill in at least one of the blanks in our knowledge of the countless floating communities of microscopic creatures in our seas, communities that have a far greater impact on our planet than many people realize.

      Says Coesel, "Just like rainforests generate oxygen and take up carbon dioxide, ocean organisms do the same thing in the world's oceans. People probably don't realize this, but these unicellular organisms are about as important as rainforests for our planet's functioning."

      U.S. Navy controls inventions that claim to change "fabric of reality"

      Inventions with revolutionary potential made by a mysterious aerospace engineer for the U.S. Navy come to light.

      U.S. Navy ships

      Credit: Getty Images
      Surprising Science
      • U.S. Navy holds patents for enigmatic inventions by aerospace engineer Dr. Salvatore Pais.
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      • While mostly theoretical at this point, the inventions could transform energy, space, and military sectors.
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      Why so gassy? Mysterious methane detected on Saturn’s moon

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      An impression of NASA's Cassini spacecraft flying through a water plume on the surface of Saturn's moon Enceladus.

      Credit: NASA
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      • A new study looked to understand the source of methane on Saturn's moon Enceladus.
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      CRISPR therapy cures first genetic disorder inside the body

      It marks a breakthrough in using gene editing to treat diseases.

      Credit: National Cancer Institute via Unsplash
      Technology & Innovation

      This article was originally published by our sister site, Freethink.

      For the first time, researchers appear to have effectively treated a genetic disorder by directly injecting a CRISPR therapy into patients' bloodstreams — overcoming one of the biggest hurdles to curing diseases with the gene editing technology.

      The therapy appears to be astonishingly effective, editing nearly every cell in the liver to stop a disease-causing mutation.

      The challenge: CRISPR gives us the ability to correct genetic mutations, and given that such mutations are responsible for more than 6,000 human diseases, the tech has the potential to dramatically improve human health.

      One way to use CRISPR to treat diseases is to remove affected cells from a patient, edit out the mutation in the lab, and place the cells back in the body to replicate — that's how one team functionally cured people with the blood disorder sickle cell anemia, editing and then infusing bone marrow cells.

      Bone marrow is a special case, though, and many mutations cause disease in organs that are harder to fix.

      Another option is to insert the CRISPR system itself into the body so that it can make edits directly in the affected organs (that's only been attempted once, in an ongoing study in which people had a CRISPR therapy injected into their eyes to treat a rare vision disorder).

      Injecting a CRISPR therapy right into the bloodstream has been a problem, though, because the therapy has to find the right cells to edit. An inherited mutation will be in the DNA of every cell of your body, but if it only causes disease in the liver, you don't want your therapy being used up in the pancreas or kidneys.

      A new CRISPR therapy: Now, researchers from Intellia Therapeutics and Regeneron Pharmaceuticals have demonstrated for the first time that a CRISPR therapy delivered into the bloodstream can travel to desired tissues to make edits.

      We can overcome one of the biggest challenges with applying CRISPR clinically.

      —JENNIFER DOUDNA

      "This is a major milestone for patients," Jennifer Doudna, co-developer of CRISPR, who wasn't involved in the trial, told NPR.

      "While these are early data, they show us that we can overcome one of the biggest challenges with applying CRISPR clinically so far, which is being able to deliver it systemically and get it to the right place," she continued.

      What they did: During a phase 1 clinical trial, Intellia researchers injected a CRISPR therapy dubbed NTLA-2001 into the bloodstreams of six people with a rare, potentially fatal genetic disorder called transthyretin amyloidosis.

      The livers of people with transthyretin amyloidosis produce a destructive protein, and the CRISPR therapy was designed to target the gene that makes the protein and halt its production. After just one injection of NTLA-2001, the three patients given a higher dose saw their levels of the protein drop by 80% to 96%.

      A better option: The CRISPR therapy produced only mild adverse effects and did lower the protein levels, but we don't know yet if the effect will be permanent. It'll also be a few months before we know if the therapy can alleviate the symptoms of transthyretin amyloidosis.

      This is a wonderful day for the future of gene-editing as a medicine.

      —FYODOR URNOV

      If everything goes as hoped, though, NTLA-2001 could one day offer a better treatment option for transthyretin amyloidosis than a currently approved medication, patisiran, which only reduces toxic protein levels by 81% and must be injected regularly.

      Looking ahead: Even more exciting than NTLA-2001's potential impact on transthyretin amyloidosis, though, is the knowledge that we may be able to use CRISPR injections to treat other genetic disorders that are difficult to target directly, such as heart or brain diseases.

      "This is a wonderful day for the future of gene-editing as a medicine," Fyodor Urnov, a UC Berkeley professor of genetics, who wasn't involved in the trial, told NPR. "We as a species are watching this remarkable new show called: our gene-edited future."

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