CHICAGO, Aug. 2 (Xinhua) -- A research team at the Marine Biological Laboratory (MBL) affiliated to the University of Chicago (UChicago) has achieved the first gene knockout in a cephalopod using the squid Doryteuthis pealeii.

The team used CRISPR-Cas9 genome editing to knock out a pigmentation gene in squid embryos, which eliminated pigmentation in the eye and in skin cells, or chromatophores, with high efficiency.

"CRISPR-Cas9 worked really well in Doryteuthis; it was surprisingly efficient," said Joshua Rosenthal, a senior scientist at MBL. Much more challenging was delivering the CRISPR-Cas system into the one-celled squid embryo, which is surrounded by an exceedingly tough outer layer, and then raising the embryo through hatching. The team developed micro-scissors to clip the egg's surface and a beveled quartz needle to deliver the CRISPR-Cas9 reagents through the clip.

The ability to knock out a gene to test its function is an important step in developing cephalopods as genetically tractable organisms for biological research, augmenting the handful of species that currently dominate genetic studies, such as fruit flies, zebrafish and mice.

It is also a necessary step toward having the capacity to knock in genes that facilitate research, such as genes that encode fluorescent proteins that can be imaged to track neural activity or other dynamic processes.

Cephalopods, including squid, octopus and cuttlefish, have the largest brain of all invertebrates, a distributed nervous system capable of instantaneous camouflage and sophisticated behaviors, a unique body plan, and the ability to extensively recode their own genetic information within messenger RNA, along with other distinctive features.

However, D. pealeii is not an ideal species to develop as a genetic research organism. It's big and takes up a lot of tank space plus, more importantly, no one has been able to culture it through multiple generations in the lab.

For these reasons, the MBL team's next goal is to transfer the new knockout technology to a smaller cephalopod species, Euprymna berryi, or the hummingbird bobtail squid, which is relatively easy to culture to make genetic strains.

The study was published Thursday in Current Biology. Enditem

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