Nuclear fusion reactions in the sun are the source of heat and light that we receive on Earth. These reactions release a massive amount 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, the situation is different. To find out what happens in a cell during space travel, scientists send baker’s yeast to the Moon as part of NASA’s Artemis 1 mission.
Cosmic damage
Cosmic radiation can damage cellular DNA, greatly increasing human risk for neurodegenerative disorders and life-threatening 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. However, ISS astronauts experience microgravity, which is another stress that can drastically alter cellular physiology.
As NASA plans to send astronauts to the Moon and then to Mars, these environmental constraints become more difficult.
The most common strategy to protect astronauts from the negative effects of cosmic rays is to physically shield them using advanced materials.
The lessons of hibernation
Several studies show that hibernators are more resistant to high doses of radiation, and some researchers 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 amazing resistance to a number of stresses, including harmful radiation. This unusual robustness comes from a class of proteins called “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 on NASA’s Artemis 1 mission, where our collection of yeast cells will travel to the moon and back in the Orion spacecraft for 42 days.
This collection contains approximately 6,000 barcoded yeast strains, where in each strain one gene is deleted. When exposed to the environment in space, these strains would start to lag if deletion of a specific gene affected cell growth and replication.
My main project in Nislow’s lab involves genetically modifying yeast cells to express tardigrade-specific proteins. We can then study how these proteins can modify the physiology of cells and their resistance to environmental stresses – especially 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, using the barcodes, the number of each strain could be counted to identify the genes and genetic pathways essential for surviving cosmic radiation-induced damage.
A model organism
Yeast has long served as a “model organism” in DNA damage studies, meaning that there is a strong basic understanding of the mechanisms in yeast that respond to DNA damaging agents. Most of the yeast genes involved in the DNA damage response have been well studied.
Despite the differences in genetic complexity between yeast and human, the function of most genes involved in DNA replication and DNA damage response have remained so conserved between the two that we can obtain extensive information on 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’s possible to automate the whole process of feeding cells and stopping them from growing in an electronic device the size of a shoebox, while culturing cells from mammals requires more space in the spacecraft and much more complex machines.
Such studies are essential to understand how the body of astronauts can cope with long-term space missions and to develop effective countermeasures. Once we identify the genes that play key roles in cosmic radiation and microgravity survival, we will be able to search for drugs or treatments that might help increase cell durability to withstand such stresses.
We could then test them in other models (like mice) before actually applying them to astronauts. This knowledge could also be potentially useful for growing plants beyond Earth.
Hamid Kian Gaikani, PhD Candidate, Pharmaceutical Sciences, University of British Columbia
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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