Author(s): Mounia Hammadi
Mentor(s): Lisa Gring-Pemble, School of Business
Human-based space missions have grown since the first humans landed on the moon. But with these intentions of human space-based expansion comes the risks of traveling into deep-space where the cosmic and ultraviolet radiations unforgivingly bombard the environment. Cosmic and ultraviolet radiations, although residing in different spectrums of the electromagnetic spectrum, have similar effects on living organisms. They are known to damage nuclear DNA within an organism through single-bond or double-bond breakages, and if not fixed, can lead to tumorigenesis and ultimately death. However, there are organisms on Earth that seem to be prepared biologically to withstand the harshest conditions that they will ever face, even those not known to them, such as the deep, radiation-filled vacuum of outer space. These unique extremophiles are known as tardigrades, and they seem to be taken for granted in the scientific community since there is not a lot of research revolving around their unique capabilities. They acquire the basic set of heat-shock and DNA repairing proteins as do other living organisms, such as the Hsp70 and the MRE11 complex proteins. However, they seem to be in a larger abundance, which provides the tardigrades with an incredibly efficient DNA and cellular repairing system compared to the average organism. Not only that, but certain species have a unique protein known as the Dsup protein, which is theorized to shield the DNA from radiation, limiting the amount of damage it would take. The experiment associated with this discovery utilized human kidney cells, a foreign cell that lacked the protein. My research involves expanding on that knowledge and figuring out other ways in which tardigrade proteins and processes can be utilized for the benefit of humanity to ensure a future where radiation is no longer of concern in space travel.
There has been an amazing push for human-based space flight.
But with that comes the increased concern of the physical toll that such an exploration can have on those involved.
Though the lack of gravity produces a multitude of risks the unfiltered, full spectrum of the cosmic and ultraviolet radiations that bombard deep-space is nothing short of a threat.
The current shielding for space shuttles is not enough to prevent radiation from coming into the spacecraft, since an increase in shielding only increases the dosage absorption.
A biological modification must be explored and the answer is a lot closer than we think.
Tardigrades, also known as “water bears” are some of Earth’s most extremophilic multicellular organisms. Originally discovered in 1773, these 8-legged microscopic creatures have been around for over 500 million years.
What makes these guys such a rare case is that they are multicellular animals with extreme tolerance to a multitude of the harshest conditions, even deep-space.
A study performed by the European Space Agency in 2007 known as “TARDIS”, no not that one, tested the limits of two species of tardigrades in the deep-vacuum of space for 10 days, which included enough dosage of cosmic radiation and raw UV radiation to cause irreversible DNA mutations which could lead to tumorigenesis, memory impairments, and ultimately death.
But not only did all the tardigrades survive the full dosage of cosmic radiation and the vacuum of space, but 12% were also able to survive the UVB-UVA spectrums, making them the first animals to survive the full conditions of outer space. Scientists determined mainly two components that makes these tiny creatures, so tough: their ability to go into a form of desiccation as well as their vast array of radio-tolerant proteins.
Desiccation, an inactive state in which a tardigrade loses 97% of the water in their body, plays a large role in their extremophilic abilities but cannot be stated with certainty to play a role during irradiation due to the contradicting data found by different experiments.
Thus, basic heat-shock proteins and DNA repairing proteins like the Hsp70 and the MRE11 proteins, just to name a few, play a large role in mending the damaged DNA as well as the cells of a tardigrade. However, these proteins are not unique to their phylum and can be found in other organisms, even us.
The protein that most scientists are interested in s known as the “Dsup” protein. Originally discovered in the Ramazzottius varieornatus species by Takuma Hashimoto and 27 other Japanese scientists, this tardigrade-unique protein is hypothesized to protect DNA, almost like a shield.
It is only hypothesized because it has only been determined that the protein is associated with the nuclear DNA.
It is not specified how.
However, an experiment utilizing human embryonic kidney cells, also known as HEK293 cells, supports this hypothesis since the scientists saw a 40% reduction in double-stranded breaks in the DNA.
Remember the first protein that I mentioned, the MRE11 protein well, it turns out that Homo sapiens, or humans, only have one gene that codes for the complex in which that protein is associated with, also known as the MRE11 complex.
This complex is a DNA damage response complex that consists of three proteins, the MRE11, the RAD50, and the “nibrin”.
And although this complex is not always error-free, it has been proven to be incredibly efficient at fixing double-stranded breaks in DNA. Keep this in mind while I tell you that tardigrades don’t just have one but four genes that codes for this specific complex.
So if humans were to obtain the same amount of MRE11 complex proteins, would it have the same effect as it does in tardigrades?
This is the premise of my research, to explore ways in which the foreign tardigrade genes can be somehow implemented for the benefit of human and plant cells in order to obtain a similar defense during space travel.
The evidence of it being a possibility is already there, as shown with the Dsup protein and the human kidney cells.
It’s just a matter of expanding on that evidence.
With the help of a George Mason University professor, Professor Lee Andrew Solomon, I will begin to research chemical and biological ways in which the tardigrade proteins and processes can be integrated into other biological organisms.
My hope is that this paper-based research will inspire scientists to explore these ideas because not only could this research create a future of human-space flight where radiation risks for astronauts and cultivated crops are mitigated but could lead to the eradication of life-threatening diseases all over the world.
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