Researchers at UCSD Study the Extreme Lives of Tardigrades

UC San Diego scientists have recently discovered the mechanism that allows tardigrades, a microscopic animal species, to survive extreme conditions. Published on Oct. 1, 2019 in the eLife journal, the study established how Dsup, a protein found only in tardigrades, functions in the animal’s body. 

Tardigrades, commonly known as water bears or moss piglets, are aquatic micro-animals that live almost everywhere on Earth. Considered extremophiles, tardigrades have been found to even be able to survive in space against the vacuum and radiation of low-Earth orbit. When not in the water, tardigrades go into a dehydrated state, allowing them to be much more resistant to outside conditions. 

With the scientific community’s increasing interest in tardigrades over the years, distinguished professor of biological sciences Dr. Jame Kardonaga found that his lab could be well-suited to do the research. 

“[Dsup] looked like a protein that had to do with chromatin (natural form of DNA packaged with proteins),” Dr. Kadonaga said to the UCSD Guardian. “We’ve been working on chromatin for the last 30 years and it looked like Dsup was a chromatin protein. So when Carolina Chavez, who was an undergraduate here, contacted me to find a lab to work in, I let her start working on it.”

The tardigrade study was written by undergraduate Carolina Chavez (now a Ph.D. student at UCLA), Postdoctoral Fellow Grisel Cruz-Becerra, Assistant Project Scientist Jia Fei, Research Scientist George A. Kassavetis, and Distinguished Professor James T. Kadonaga.

Previous research on tardigrades had already made the connection between Dsup and its protection against X-rays, but research had yet to indicate how this mechanism works. Through this new study, the UCSD scientists were able to fill in this gap of knowledge.  

“X-rays create hydroxyl radicals that hit the DNA,” Dr. Kadonaga said. “We found that the Dsup binds to [units of chromatin], creating a protective cloud that protects the cell from hydroxyl radicals. That explains how Dsup proteins make cells resistant to X-rays.”

With this link, the scientists were able to understand how Dsup functions in tardigrades and how the protein creates a protective barrier. This barrier in turn would make possible practical applications when applied to humans.

“Theoretically, if you add Dsup to [human] cells, it could promote cell longevity and durability,” Dr. Kadonaga said. “Some pharmaceuticals are made with cultured hamster cells; [with Dsup], you might be able to make the cells tougher. It might even be possible to use [Dsup] in cell-based therapies for cancer by modifying blood T cells to be tougher.”

The study also made an additional discovery but has yet to fully fathom those results. It turns out that Dsup has a particular binding pattern that is very similar to a binding protein for chromatin that is found exclusively in vertebrates. The connection between the binding protein in tardigrades and vertebrates has yet to be explained. For now, the scientists are continuing to study Dsup to better understand the protein’s functions. 

“Our immediate goal is to get a more precise understanding of what the protein does,” Dr. Kadonaga said. “We want to narrow down exactly what part of the protein binds to the [chromatin unit]. We also wanted to understand each of the functional regions of Dsup. This could be useful for the applications of the protein I talked about: if we really understood all the working parts, we might be able to engineer an improved version of Dsup.”

Following the release of the paper, tardigrade experts from around the world reached out to the team to commend their work and provide positive feedback. 

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