See-through Squid Lets Scientists Study Cephalopod Nervous System

“The ability to directly and precisely test gene function in a model cephalopod is exciting because it makes it possible to study the features that make cephalopods special - and it will be an important tool for understanding many different aspects of their unique biology,” said co-author Albertin.

The team established the albino lineage of E. berryi by deactivating the genes for two pigmentation enzymes using CRISPR-Cas9 genome editing. Then, co-authors Cris Niell at University of Oregon, Eugene, and Ivan Soltesz at Stanford University examined the albino squid’s brain activity by inserting a fluorescent dye into its optic lobe. This dye glows every time it detects calcium, which the brain releases when it fires. They then 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.

This discovery “allows us to look at gene function and cephalopod brains in ways we couldn't before,” said Rosenthal. If other scientists want to understand how signals are relayed through cephalopod brains, they can now breed albino squid and do similar experiments with calcium-activated dye. Or, if a researcher wants to genetically alter these squid to study other aspects of their biology, the team’s research demonstrates that such experiments are possible.

In this study, Rosenthal and Albertin’s team discovered a new facet of E. berryi’s biology. When the team deactivated the first 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. The resulting E. berryi offspring, however, were still pigmented. The team 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.

Rosenthal, Albertin and colleagues hope other scientists decide to expand our understanding of E. berryi and use them to unlock some of the mysteries of cephalopod biology.

“We want to see these animals shared with the research community,” Rosenthal said. “Cephalopods contain treasure troves of biological novelty. We want to see people using them to ask thought-provoking questions and come up with novel findings.”

In addition to Rosenthal and Albertin, the team included first author Namrata Ahuja from the Marine Biological Laboratory; Ruhina Rafiq, Sal Nemes, Taylor Sakmar, Miranda A Vogt, Bret Grasse, Juan Diaz Quiroz, Ryan Wesley Null, Danielle Nicole Dallis, and Lisa Abbo from the Marine Biological Laboratory; and collaborators from Stanford University, University of Oregon-Eugene, Columbia University, Okinawa Institute of Science and Technology Graduate University, University College London, and University of California-Berkeley.

Citation:

Namrata Ahuja, et al (2023) Creation of an albino squid line by CRISPR-Cas9 and its application for in vivo functional imaging of neural activity. Current Biology, DOI: https://doi.org/10.1016/j.cub.2023.05.066

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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery – exploring fundamental biology, understanding marine biodiversity and the environment, and informing the human condition through research and education. Founded in Woods Hole, Massachusetts in 1888, the MBL is a private, nonprofit institution and an affiliate of the University of Chicago.