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Monsters of the Deep Could Help Protect You From the
Monsters Within
Dylan Pariseau and Katherine Kiley
Keene State College Biology Department
Abstract
Sharks are an important part of our ecosystem, and some are the
longest living vertebrates on our planet. The Shark Genome has
evolved over hundreds of millions of years to give the organisms
one of the most astounding wound healing and immune systems
know to vertebrates. New studies of shark DNA shows that
changes in their immunity genes may explain why their wounds
heal so quickly and how adaptive immunity arose in gnathostomes.
Significantly, sharks have an astoundingly low occurrence of
cancer. Specifically, there are two genes in sharks that help to
prevent cancer whose counterparts in humans actually can
contribute to cancer. What we are investigating is the difference
between the shark and human genes due to different evolutionary
paths. One way to begin to investigate this difference is by looking
at a model genome that evolves very slowly. One study of Elephant
sharks found that they are evolving much slower than all other
known vertebrates. This along with their primitive form of adaptive
immunity makes them an excellent model genome to compare
other vertebrates, such as sharks and humans, against.
Introduction and Background
•You are more likely in your lifetime to be struck by lightning than
attacked by a shark
•Some shark fossils date back to 420-450 million years ago
•Jawed vertebrates are called gnathostomes but jaws were not
the only thing to arise with this group. Immunoglobulin based
adaptive immunity evolved from this group and the group
eventually split in to cartilaginous fish and boney vertebrates.
Sharks evolved from the cartilaginous branch while humans from
the boney.
Results
Discussion
•The phylogenetic trees show the inferred evolutionary relationship
amongst various species. It also shows their phylogeny based
upon similarities and differences in their genetic and possibly
physical characteristics.
In Figure 6 the investigation of the Bag1 gene yields results
that would be expected when considering evolution. We would
expect that the elephant shark would be more closely related
to other sharks than to humans. We would also expect the
coelacanth and platypus to be closer related to each other and
humans than to sharks because of their closer relation to bony
fish than cartilaginous fish. This predicted relationship is not
what we saw upon analysis of the Legumain gene. Figure 7 is
the phylogenetic tree that we got from our analysis and the
expected evolutionary relation that the analysis of the Bag1
gene showed is not completely seen here. Instead of the
elephant shark legumain gene being more closely related to
sharks it is shown to be closer to that of humans and platypus.
As previously mentioned the elephant shark has the slowest
evolving genome of all vertebrates, and the platypus has the
slowest out of all mammals. We believe that this is a factor into
why the expected evolutionary relationship isn't seen here. It is
however interesting that the elephant shark legumain gene is
still more closely related to humans. In the future, we believe
this relationship should be further investigated to gain further
knowledge of this genes evolution and its effects in cancer. It
must also be addressed that in the legumain tree there was no
coelacanth due to the lack of sequencing of its gene. If this
gene is sequenced in the future, it should be included in the
tree to have a more complete investigation. We believe that
this investigation demonstrates how much more we have to
learn about sharks and their impacts to not only our health but
evolution itself. To be able to investigate these magnificent
creatures for many years to come there needs to be a healthy
population. We believe that not just for their sake but for ours
as well that conservation efforts need to be increased to
protect these organisms that make up such a vital part of our
ecosystem.
Figure 2. Elephant Shark
Figure 3. PETA shark conservation propaganda
Genetic Investigation
•Legumain and Bag1 are the genes of interest that have counter
parts in humans.
•In Humans the Bag1 gene actually inhibits apoptosis thus its
over expression is associated with cancer. The Legumain gene is
important to immune function and has been shown to be over
expressed in human cancers.
•To investigate these two genes we performed a phylogenetic
analysis of different species that we thought could give particular
insight into the evolution of these genes.
•We strategically picked different species for either their relation
to the two of utmost interest (sharks and humans) or for how little
their genome has been derived due to their rate of evolution.
Figure 6. Phylogenetic tree of Bag1 gene
•Although the elephant shark is the slowest evolving vertebrate
the slowest evolving mammal is the platypus. We decided to
include both the platypus and the elephant shark in our analysis
to compare the shark and human genes to the slowest evolving
species that they are more closely related to than each other.
Works Cited
•Another species that we included because of its minimal amount
of derivation due to evolution was the coelacanth (also called “the
living fossil”) and is known to be one of the closest living fish
relative of modern day mammals.
Marra, N. J., Richards, V. P., Early, A., Bogdanowicz, S. M., Bitar, P. D. P.,
Stanhope, M. J., & Shivji, M. S. (2017). Comparative transcriptomics of
elasmobranchs and teleosts highlight important processes in adaptive
immunity and regional endothermy. BMC genomics, 18(1), 87.
Venkatesh, B., Kirkness, E. F., Loh, Y. H., Halpern, A. L., Lee, A. P., Johnson,
J., ... & Strausberg, R. L. (2006). Ancient noncoding elements conserved in
the human genome. Science, 314(5807) 1892-1892.
Alam, M. T., Petit, R. A., Read, T. D., & Dove, A. D. (2014). The complete
mitochondrial genome sequence of the world's largest fish, the whale shark
(Rhincodon typus), and its comparison with those of related shark species.
Gene, 539(1), 44-49.
Department of Vertebrate Zoology. (n.d.). Retrieved April 20, 2017, from
http://vertebrates.si.edu/fishes/coelacanth/coelacanth_wider.html
Venkatesh, B., Lee, A. P., Ravi, V., Maurya, A. K., Lian, M. M., Swann, J. B., ...
& Hoon, S. (2014). Elephant shark genome provides unique insights into
gnathostome evolution. Nature, 505(7482), 174-179.
Trinajstic, K., Marshall, C., Long, J., & Bifield, K. (2007, April 22). Exceptional
preservation of nerve and muscle tissues in Late Devonian placoderm fish and
their evolutionary implications. Retrieved April 21, 2017, from
http://rsbl.royalsocietypublishing.org/content/3/2/197
•In addition, we also included many shark species to find which of
those investigated genes are closest to humans.
•The phylogenetic trees were formed using a combination of
BLAST and MEGA.
Figure 1. Evolution of gnathostomes
•Elephant sharks have subsets of helper T cells that are very
restricted in what they can do. This combined with the fact of their
slow evolution allows us to know more about the evolution of our
own adaptive immunity.
Figure 5. Coelacanth
• Between 2000 and 2011 North American shark populations
decreased by 80%.
•1 in 6 species of sharks, rays and skates are considered
threatened to become extinct.
Figure 4. Platypus
Figure 7. Phylogenetic tree of legumain gene
Thank you to Dr. Loren Launen, Brian Moore, Nova Southeastern University,
Keene State Bioinformatics, University of New Hampshire and Cornell
University