Water bears are not actually bears at all, in any sense of the word. Living in water, eight-legged and less than 0.05 inches in length, they don’t resemble bears in any way, but their name is hardly the most unusual thing about them. Formally called tardigrades, they are extremophiles, one of those creatures that survive under extreme conditions; they have been known to survive through temperatures well above 200 degrees Fahrenheit and close to absolute zero (minus 460 degrees Fahrenheit), live for months without food and water despite being aquatic, as well as withstand high pressure, strong radiation and even the vacuum of outer space.
Now, researchers from the University of Tokyo have identified a protein in a tardigrade species that is responsible for protecting it from damage caused by radiation. In a statement Wednesday, they say the “protein can protect the DNA of human cultured cells from otherwise lethal amounts of radiation damage.”
The scientists sequenced the entire genome of Ramazzottius varieornatus — a particularly hardy tardigrade species that can survive high doses of radiation — and found a new protein that protects its DNA under irradiation. The researchers gave the protein a simple name — Dsup, short for Damage Suppressor.
Next, they took some human cultured cells and manipulated them to be able to create the Dsup protein. They found that when exposed to X-rays, which would ordinarily damage their DNA, the cultured cells showed only about half the damage expected, and to their surprise, they found those cells were still capable of reproducing. X-ray induced damage in the human cells with Dsup was suppressed by about 40 percent, which even though a lot lower than the resilience of tardigrades, is significant.
“What’s astonishing is that previously, molecules that repair damaged DNA were thought to be important for tolerating radiation. On the contrary, Dsup works to minimize the harm inflicted on the DNA,” Takuma Hashimoto, one of the lead authors of the study, said in the statement.
“After exposing the cultured cells to X-rays, initially, we found only a small difference between those with and without Dsup; however, we left them in the incubator for a while in the hope that a key property of Dsup lay hidden somewhere in that miniscule difference, and that the difference would eventually become quite distinct. To our great surprise, when we checked the cells under the microscope some time later, their shape and number had changed significantly, far beyond our expectations,” he added.
The research is useful because it has many potential applications, particularly in the field of medicine, especially for people undergoing radiation therapy. If scientists could devise a way of preventing DNA damage caused by radiation, therapies that use it would become a lot safer.
The researchers “believe that their precise tardigrade genome sequence is a treasure trove of other Dsup-like proteins.” Lead co-author Takekazu Kunieda said: “While researchers have long been fascinated by their resilience, we still don’t really know how it’s possible. We need to find the molecules that allow tardigrades to tolerate such conditions.”
The study was published Tuesday in the journal Nature Communications, under the title “Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein.”