Genome of Steller's sea cow decoded
Giants of the Ice Age

Date:
February 8, 2022
Source:
Universita"t Leipzig
Summary:
During the Ice Age, giant mammals such as mammoths, sabre-toothed
cats and woolly rhinoceroses once roamed Northern Europe and
America. The cold oceans of the northern hemisphere were also
home to giants like Steller's sea cow, which grew up to eight
meters long and weighed up to ten tons, and has been extinct
for around 250 years. Now an international research team has
succeeded in deciphering the genome of this ice-age species from
fossil bones. They also found an answer to the question of what the
genome of this extinct species of sea cow reveals about present-day
skin diseases.



FULL STORY ========================================================================== During the Ice Age, giant mammals such as mammoths, sabre-toothed cats
and woolly rhinoceroses once roamed Northern Europe and America. The cold oceans of the northern hemisphere were also home to giants like Steller's
sea cow, which grew up to eight meters long and weighed up to ten tons,
and has been extinct for around 250 years. Now an international research
team has succeeded in deciphering the genome of this ice-age species
from fossil bones. They also found an answer to the question of what
the genome of this extinct species of sea cow reveals about present-day
skin diseases.


==========================================================================
The giant sea cow from the Ice Age was discovered in 1741 by Georg
Wilhelm Steller and later named after him. The 18th-century naturalist was interested not only in the enormous size of this animal species but also
in its unusual, bark-like skin. He described it as "a skin so thick that
it is more like the bark of old oaks than the skin of an animal." Such a bark-like structure of the epidermis is not found in related sirenians,
which today live exclusively in tropical waters. In scientific circles,
it was previously assumed that the bark-like epidermis was the result
of parasite feeding, but also insulated heat and thus protected the sea
cow well from the cold during the Ice Age and from injuries in the polar
seas. In the current study, the scientists led by Dr Diana Le Duc and
Professor Torsten Scho"neberg from Leipzig University, Professor Michael Hofreiter from the University of Potsdam and Professor Beth Shapiro from
the University of California, show that the palaeogenomes of Steller's
sea cow reveal functional changes. These changes were responsible for
the bark-like skin and the adaptation to cold.

To find this out, an international research team from Germany and the
US reconstructed the genome of this extinct species from fossil bone
remains of a total of twelve different individuals. "The most spectacular result of our investigations is that we have clarified why this giant
of the sea had bark- like skin," said Diana Le Duc from the Institute
of Human Genetics at Leipzig University Hospital. The scientists found inactivations of genes in the sea cow genome that are necessary for the
normal structure of the outermost layer of the epidermis. These genes
are also used in human skin. "Hereditary defects in these so-called lipoxygenase genes lead to what is known as ichthyosis in humans. This
is characterised by a thickening and hardening of the top layer of
skin with large scales, and is sometimes also known as 'fish scale
disease'," said Scho"neberg from the Rudolph Scho"nheimer Institute
of Biochemistry. "The results of our research thus also sharpen our
view of this clinical picture," explained the biochemist, adding:
"Here may lie the key to new therapeutic approaches." The scientists pinpointed the genetic defect by comparing the genome with that of the
closest relative, the dugong. The researchers received support with
their investigations from the Max Planck Institute for Evolutionary Anthropology in Leipzig, which contributed its bioinformatics expertise
in the analysis of ancient DNA. As a result, they identified important
evidence of genetic changes that may have contributed to adaptation to
the cool North Pacific habitat. "This is an impressive example of how gene defects can not only cause disease, but also have advantages depending on
the habitat," said Hofreiter from the University of Potsdam. Furthermore,
the genome data revealed a dramatic reduction in population size. This
began 500,000 years before the species was discovered and may have
contributed to its extinction. Hofreiter summed it up as follows: "With
today's molecular genetic clarification, our study closes the circle of
an exact observation by a German naturalist in the early 18th century." ========================================================================== Story Source: Materials provided by Universita"t_Leipzig. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Diana Le Duc, Akhil Velluva, Molly Cassatt-Johnstone, Remi-Andre
Olsen,
Sina Baleka, Chen-Ching Lin, Johannes R. Lemke, John R. Southon,
Alexander Burdin, Ming-Shan Wang, Sonja Grunewald, Wilfried
Rosendahl, Ulrich Joger, Sereina Rutschmann, Thomas B. Hildebrandt,
Guido Fritsch, James A. Estes, Janet Kelso, Love Dale'n, Michael
Hofreiter, Beth Shapiro, Torsten Scho"neberg. Genomic basis for
skin phenotype and cold adaptation in the extinct Steller's sea
cow. Science Advances, 2022; 8 (5) DOI: 10.1126/sciadv.abl6496 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220208105222.htm
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