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By Hamid Kian Gaikani, Ph.D., Pharmaceutical Sciences, University of British Columbia
Nuclear fusion reactions in the sun are the source of heat and light we receive on Earth. These reactions release massive amounts of cosmic radiation, including X-rays and gamma rays, and charged particles that can be harmful to any living organism.
Life on Earth has been protected by a magnetic field that forces charged particles to bounce from pole to pole, as well as an atmosphere that filters out harmful radiation.
During space travel, however, it is a different situation. To find out what happens in a cell when it travels to outer space, scientists are sending baker’s yeast to the Moon as part of NASA’s Artemis 1 mission.
cosmic damage
Cosmic radiation can damage cellular DNA, significantly increasing the human risk of neurodegenerative disorders and fatal diseases, such as cancer. Because the International Space Station (ISS) is located in one of Earth’s two Van Allen radiation belts, which provides a safe zone, astronauts are not overly exposed. Astronauts on the ISS do, however, experience microgravity, which is another stress that can dramatically change cellular physiology.
As NASA plans to send astronauts to the Moon and, later, to Mars, these environmental stresses become more challenging.
The most common strategy to protect astronauts from the negative effects of cosmic rays is to physically shield them with state-of-the-art materials.
Lessons from hibernation
Several studies show that hibernators are more resistant to high doses of radiation, and some scholars have suggested the use of “synthetic or induced torpor” during space missions to protect astronauts.
Another way to protect life from cosmic rays is to study extremophiles, organisms that can remarkably tolerate environmental stresses. Tardigrades, for example, are micro-animals that have shown surprising resistance to a range of stresses, including harmful radiation. This unusual robustness comes from a class of proteins known as “tardigrade-specific proteins.”
Under the supervision of molecular biologist Corey Nislow, I use baker’s yeast, Saccharomyces cerevisiae, to study cosmic DNA damage stress. We are participating in NASA’s Artemis 1 mission, where our collection of yeast cells will travel to the Moon and back on the Orion spacecraft for 42 days.
This collection contains about 6,000 barcoded yeast strains, where a gene is deleted in each strain. When exposed to the environment in space, these strains would begin to lag if the deletion of a specific gene affects cell growth and replication.
My main project in the Nislow lab is genetically engineering yeast cells to express tardigrade-specific proteins. We can then study how these proteins can alter the physiology of cells and their resistance to environmental stresses, particularly radiation, in the hope that this information will be useful when scientists try to engineer mammals with these proteins.
When the mission is complete and we receive our samples back, using the barcodes, the number of each strain could be counted to identify genes and gene pathways essential for surviving damage induced by cosmic radiation.
A model organism
Yeast has long served as a “model organism” in DNA damage studies, meaning that there is a solid background knowledge of the mechanisms by which yeast respond to DNA-damaging agents . Most of the yeast genes that play a role in the DNA damage response have been well studied.
Despite differences in genetic complexity between yeast and humans, the function of most genes involved in DNA replication and the DNA damage response has remained so conserved between the two that we can obtain a large number of ‘insight into the DNA damage response of human cells by studying yeast. .
Also, the simplicity of yeast cells compared to human cells (yeast has 6,000 genes while we have over 20,000 genes) allows us to draw stronger conclusions.
And in yeast studies, it is possible to automate the entire process of feeding cells and stopping their growth in an electronic device the size of a shoebox, while growing cells from mammal requires more space in the spacecraft and much more complex machinery.
These studies are essential to understanding how astronauts’ bodies can cope with long-term space missions and to develop effective countermeasures. Once we identify the genes that play a key role in surviving cosmic radiation and microgravity, we could look for drugs or treatments that can help increase the durability of cells to withstand these stresses.
We could then test them in other models (such as mice) before applying them to astronauts. This knowledge could also potentially be useful for growing plants beyond Earth.
This article is republished from The Conversation under a Creative Commons license.