The hummingbird bobtail squid (Euprymna berryi) is a genetically tractable cephalopd model system. Credit: Tim Briggs/MBL Cephalopod Program
Key points:
- Researchers used CRISPR-Cas9 to engineer an albino squid.
- The achievement gives scientists a look into the working nervous system of a cephalopod for the first time.
- The study establishes E. berryi as a cephalopod model organism for neurobiological research.
In a first, researchers at the Marine Biological Laboratory (MBL) have genetically engineered an albino strain of the hummingbird bobtail squid, Euprymna berryi. The result is a nearly transparent organism that offers scientists clear optical access to visualizing the nervous system in a living cephalopod for the first time.
While trying to engineer an albino squid, the MBL team accidentally discovered a new facet of E. berryi’s biology. When they deactivated the pigmentation gene, called TDO, they expected to produce an albino squid, as they had done with another species of squid (Doryteuthis) in a 2020 study. But, the resulting E. berryi offspring were still pigmented. The scientists soon realized the pigment was also being generated by a second enzyme called IDO, a protein previously unknown in cephalopods. Why E. berryi has two enzymes that seem to perform the same function remains unknown.
The researchers then deactivated both pigmentation enzymes using CRISPR-Cas9. Working with collaborators at Stanford University, the research team then examined the albino squid’s brain activity by inserting a fluorescent dye into its optic lobe. The dye glows every time it detects calcium, which the brain releases when it fires.
For the study, published in Current Biology, the scientists projected a series of images onto a screen in front of the squid, causing its optic lobe to activate and the dye to light up, all of which was captured using an imaging microscope. When the team tried the same technique with a wild-type squid, its skin pigmentation prevented them from seeing the dye clearly.
The study presents Euprymna berryi as a model organism for neurobiological and other types of research.
“There’s a whole lot of incredibly interesting biology surrounding cephalopods, unlike any other invertebrate,” said MBL Senior Scientist Joshua Rosenthal. “We now have a model cephalopod where we can interrogate biological function at much higher resolution than before.”