Sep 23 2016

Tardigrade Radiation Shield

tardigrade1Tardigrades (also called water bears or moss piglets) are one of the coolest animals on earth. They are microscopic, live pretty much anywhere there is water, and are “extremotolerant.” When they lack water they just dry up, and their dessicated form can survive extremes of temperature, high pressure, and even the vacuum of space. Just add water back, and they plump up and go about their business.

They are also very tolerant to radiation, an enviable property. Recently scientists studied the tardigrade genome – more specifically, R. varieornatus, which is one of the hardiest species. There are about 1000 known species of tardigrades and probably a couple thousand more waiting to be described. They had a couple of questions.

First, they wanted to follow up on prior research showing that tardigrades have an extremely high percentage of genes acquired through horizontal transfer from bacteria. This result was not replicated in the current study, which found a very low amount, only about 1.3%. The higher result had already been called into question by other researcher, and this it pretty much the final nail in the coffin.

More interestingly, the researchers were trying to discover the mechanism by which R. varieornatus is so tolerant to radiation. It was originally thought that tardigrades simply had robust DNA repair mechanisms to help them survive extreme radiation damage. That might still be the case, but the researchers found a novel tardigrade protein they named Dsup (for damage suppressor) that wraps itself around the tardigrade DNA and acts as a radiation shield.

To demonstrate that Dsup has protective properties, they took human kidney cells and inserted the Dsup gene into them. When they cultured those human-Dsup cells and exposed them to radiation they found that they experienced 40% less DNA damage than control cells.

That is an amazing result, especially for the first round of experiments. This degree of protection is less than what R. varieornatus has, so the little buggers likely still have many secrets up their 8 wrinkles sleeves.

The possible implications of this research are significant. First, I think it clearly establishes that tardigrades are a potentially deep source of research into novel proteins that have interesting and useful effects. They have evolved to survive extreme conditions, and we may be able to benefit from that evolutionary laboratory.

Specifically, radiation protection can be extremely useful. Radiation exposure is a risk factor for cancer, because ionizing radiation breaks chemical bonds, including those in DNA, resulting in mutations which sometimes cause cancer. Some professions carry a higher risk of exposure to radiation.

Radiation exposure may be the ultimate limiting factor for human colonization of space and other worlds. According to

The Mars rover Curiosity has allowed us to finally calculate an average dose over the 180-day journey. It is approximately 300 mSv, the equivalent of 24 CAT scans. In just getting to Mars, an explorer would be exposed to more than 15 times an annual radiation limit for a worker in a nuclear power plant.

This is just for getting to Mars. There is more radiation exposure on the planet surface (no protective magnetic field or thick atmosphere) and then another round on the trip home.

If we ever want to get people to Mars we will have to design ships with sufficient radiation shielding, and have habitats waiting for them on Mars which also have heavy shielding. Even with tardigrade level radiation resistance, shielding will be necessary.

However, radiation exposure is likely to be an occupational hazard of exploring and living off Earth. It wouldn’t hurt to equip astronauts and Mars colonists with some extra radiation resistance.

But – how plausible is it that we will be able to use Dsup to protect people from radiation? Right now it seems like we would have to genetically engineer people with the Dsup gene. Despite the early success with kidney cells, this is not likely to happen without decades of further research.

At the very least we would need to conduct animal research on several species, examining them over years, to see what all the effects of Dsup are. It might turn out that there are no downsides to incorporating Dsup into your cells, but that will take a lot of research to prove.

There are also likely to be ethical and regulatory hurdles. We then also have to decide who gets the upgrade. Do we simply offer it as a service to any perspective parents who want radiation-tolerant children? Perhaps it will be offered to people who plan on being Mars colonists and having children there.

Another possible application is gene therapy – using some mechanism to insert the Dsup gene into living people. This is a bit ethically easier, since people can just decide for themselves if they want the alteration. Gene therapy, however, remains a tricky technology and is not yet ready for prime time. We would need to get the Dsup gene into most of your cells, and right now we don’t have the technology to safely do that. That is likely to change, however.


This one study, finding the Dsup protein and gene in tardigrades and its protective effect for human cells, may be a window into the near future. Genetic engineering technology is getting cheaper and easier (think CRISPR).

We are likely do discover or invent all sorts of novel proteins that could have dramatic properties. How much are we willing to alter the human species? Adoption of technology is always hard to predict, but it seems to me the potential benefits will eventually wear down resistance. Once we open that box, let’s say by making radiation-resistant Mars colonists, it will be easier to approve the next upgrade.

It is interesting to think about how far this will go, and on what time frame.

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