Abstract
Tardigrades represent a phylum of very small aquatic animals in which many species have evolved adaptations to survive under extreme environmental conditions, such as desiccation and freezing. Studies on several species have documented that tardigrades also belong to the most radiation-tolerant animals on Earth. This paper gives an overview of our current knowledge on radiation tolerance of tardigrades, with respect to dose-responses, developmental stages, and different radiation sources. The molecular mechanisms behind radiation tolerance in tardigrades are still largely unknown, but omics studies suggest that both mechanisms related to the avoidance of DNA damage and mechanisms of DNA repair are involved. The potential of tardigrades to provide knowledge of importance for medical sciences has long been recognized, but it is not until recently that more apparent evidence of such potential has appeared. Recent studies show that stress-related tardigrade genes may be transfected to human cells and provide increased tolerance to osmotic stress and ionizing radiation. With the recent sequencing of the tardigrade genome, more studies applying tardigrade omics to relevant aspects of human medicine are expected. In particular, the cancer research field has potential to learn from studies on tardigrades about molecular mechanisms evolved to maintain genome integrity.
Highlights
Tardigrades belong to the smallest invertebrates with a body length that may reach 1 mm in the largest species, but usually is in the range of 0.25–0.50 mm
H. exemplaris, were exposed to UVC doses of 2.5–20 kJm−2, and the results showed a clear difference in sensitivity between the species and between irradiation in the hydrated and desiccated state in
Both mechanisms that prevent damage to DNA (e.g., reactive oxygen species (ROS) scavengers) and repair damage to DNA are likely involved in the desiccation/radiation tolerance of tardigrades, and the emerging understanding of these mechanisms should be of interest to cancer research
Summary
Tardigrades belong to the smallest invertebrates with a body length that may reach 1 mm in the largest species, but usually is in the range of 0.25–0.50 mm They are essentially aquatic animals, requiring to be surrounded by water in order to maintain their hydroskeleton function and for uptake of oxygen through the cuticle. They represent a specific phylum, Tardigrada, which currently includes around 1300 described species [1,2,3] from a variety of terrestrial, freshwater and marine ecosystems. This review gives a brief overview of our knowledge on radiation tolerance in tardigrades, the possible molecular mechanisms behind the tolerance, and the potential importance of tardigrade tolerance research to medical sciences with an emphasis on cancer
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