Researchers have used CRISPR–Cas9 genome-editing technology to make squid transparent — the first use of CRISPR in cephalopods, a class of marine invertebrates.
Cephalopods have large brains, complex behaviours and neurons that directly control the changing patterns on their skin, making them a promising model organism for studying brain evolution and neural function. Joshua Rosenthal at the Marine Biological Laboratory in Woods Hole, Massachusetts, and his colleagues used CRISPR–Cas9 to delete a gene called TDO from embryos of the longfin inshore squid (Doryteuthis pealeii). The protein encoded by TDO helps to add pigment to the animal’s eyes and chromatophores — colour-changing cells that allow cephalopods to blend into their environments.
Knocking out TDO made the animals transparent. CRISPR successfully deleted TDO in more than 90% of the animals’ cells, suggesting that the technology could be similarly efficient in modifying genes involved in cephalopod brain function.
The researchers say that their next step is to modify the hummingbird bobtail squid (Euprymna berryi), which is smaller and easier to maintain in laboratories.