Squid edit their RNA to keep cellular supply lines moving in the cold

WASHINGTON — Squid don’t have thermostats to control ocean temperatures. Instead, the cephalopods tweak RNA to adjust to frigid waters, a study suggests.

Usually, genetic instructions encoded in DNA are faithfully copied into messenger RNA, or mRNA, and then into proteins. But squid and other soft-bodied cephalopods edit many of their mRNAs so that the resulting proteins contain some different building blocks than are inscribed in DNA (SN: 3/25/20; SN: 4/6/17). 

“In these animals, 60 percent or more of their proteins are actually recoded. This is astonishing in comparison to how [rarely RNA] editing is used in mammals,” molecular biologist Kavita Rangan said December 5 at Cell Bio 2022, the annual joint meeting of the American Society for Cell Biology and the European Molecular Biology Organization.

Rangan, of the University of California, San Diego, examined the consequences that editing has on proteins called kinesins. Those molecular motors ferry cargo throughout cells along protein tracks called microtubules. Problems on the cellular railway can lead to cells’ disfunction or death and may contribute to disease (SN: 12/12/19).

Squid hatchlings put in chilly 6° Celsius water for a day edited mRNAs for a kinesin protein differently and more heavily than hatchlings placed in warm 20° C water, Rangon found.

She then made an unedited version and several edited versions of kinesin in the laboratory and compared the proteins’ movements on microtubules. In the cold, unedited kinesin moved more slowly, traveled shorter distances and fell off microtubule tracks more often than it did when warm.

Two of the edited kinesins, like those made by squid in cold water, moved a little slower than the unedited protein. But the renovated versions grabbed on to microtubules more often and had longer runs than unedited kinesin. “This suggests that recoding can allow kinesin to stay on its tracks and travel farther” in the cold, Rangan said.

Changing some made-on-demand RNAs instead of permanently altering DNA may give squid more flexibility to adjust to fluctuating ocean temperatures, she said.