Weddell Seal: a champion diver

Weddell Seal: a champion diver

Fig 1

“A person who can swim unaided to a depth of 20 meters and stay submerged for three minutes is considered an expert diver. Yet such an accomplishment pales when compared with that of another mammal, one able to plunge more than 500 meters and remain underwater for more than 70 minutes. This diving virtuoso is the Weddell seal (Leptonychotes weddelli, Fig.1), a member of the Phocidae family of true, or earless, seals.”

So began a 1987 article in Scientific American, authored by Warren M Zapol, Emeritus Anesthetist-in-Chief and director of the Anesthesia center for Critical Care Research (ACCCR) at Massachusetts General Hospital (MGH). Dr. Zapol first traveled to Antarctica (the “Ice”) in 1975. He would return 7 more times, often accompanied by world-renowned biomedical researchers, including Dr. Peter Hochachka and Sir Graham C. (“Mont”) Liggins, to continue his studies of marine mammal diving. Over the course of 3 decades, their work yielded great insights into mammalian adaptations for diving.

Fast forward to 2009 when Dr. Zapol asked a junior faculty member in the Anesthesia Center for Critical Care Research at MGH (Dr. Manu Buys) to rummage through the -80°C freezer and find some Weddell seal lung tissue stored there since the early 90s. The goal was to start developing molecular tools (e.g. PCR primers), to test the hypothesis that alterations in a very specific cell signaling pathway (the nitric oxide or NO system) were responsible for Weddell’s ability to withstand long bouts of severe hypoxia.

What started as a “side project” for Dr. Buys quickly took over his scientific life as he and Dr. Zapol decided the logical next step was to sequence the Weddell seal genome. In July of 2010, with the help of Dr. Mark Borowsky, director of the Illumina sequencing core at MGH, the Weddell seal was added to the list of mammals to be sequenced at the Broad Institute in the framework of the mammalian genome project, led by Dr. Kerstin Lindblad-toh, and assisted by Dr. Federica Di Palma, Dr. Jessica Alföldi, and project manager Jeremy Johnson.

The next challenge was to obtain high quality Weddell seal tissue from which genomic DNA could be prepared for sequencing. Dr. Zapol and Dr. Buys reached out to colleagues on the ice (Dr. Robert Garrott and Dr. Jay Rotella, both Professors of Ecology at Montana State University; Dr. Daniel Costa, Professor of Ecology and Evolutionary Biology at the University of California at Santa Cruz (UCSC); and Dr. Jennifer Burns, Professor of Biological Sciences at the University of Alaska Anchorage), who agreed to collect and ship samples from Antarctica to the Broad Institute.

“We have DNA!”

Fig 2

After several failed attempts to isolate sequencing-quality genomic DNA from blood samples, the next milestone was reached on March 11 2011. Marcia Lara (at the time Senior Manager, Genome Sequencing Sample Repository and Biological Samples Platform at the Broad Institute) confirmed that her lab had successfully isolated record high molecular weight DNA from liver tissue from one Weddell seal (designated WS11-02, Fig 2). Soon after, sequencing was initiated at the Broad Institute. Preliminary results became available in the fall of 2012 and the assembled genome was uploaded to NCBI in March 2013.

National Science Foundation funding

While the geneticists at the Broad were working their magic, Dr. Buys and Dr. Zapol submitted, in June 2011, a research project to the National Science Foundation entitled “Decoding the master switch of life: using emerging genomic information to characterize nitric oxide (NO) signaling in the cardiovasculature of the Weddell seal.” Over the next 3 years, the science in the proposal evolved, and 2 bright marine biologists were added to the team, Dr. Jessica Meir and Dr. Allyson Hindle. Dr. Jessica Meir earned her doctorate from Scripps Institution of Oceanography studying penguins in Antarctica and California’s Northern elephant seals before moving on to the University of British Columbia (UBC) in Vancouver, Canada. There Dr. Meir studied bar-headed geese, which she trained to fly in a wind-tunnel, for their special abilities: they manage to migrate over the Himalaya, conquering the cold, wind and low oxygen conditions of the mountains. In 2013 Dr. Meir was selected as a member of NASA’s 2013 Astronaut Candidate Class where she recently earned her astronaut pin. Dr. Allyson Hindle earned her doctorate at Texas A&M University where she participated in her first trips to Antarctica to study Weddell seal diving. She also completed a postdoc at UBC and then moved on to studying another example of extreme physiology in mammals¾hibernation. Both Dr. Meir and Dr. Hindle were instrumental in moving the project forward and finally, in 2014 the NSF awarded a grant (“Unraveling the Genomic and Molecular Basis of the Dive Response: Nitric Oxide Signaling and Vasoregulation in the Weddell Seal”) to a team consisting of members from UCSC (Dr. Daniel Costa and Dr. Luis Huckstadt) and from the ACCCR (Ms. Kaitlin Allen, Dr. Buys, Dr. Hindle, and Dr. Zapol). The team, call-sign B-267, has been preparing frantically to deploy to the largest research base US Antarctic Program (USAP) later this Fall. Ms. Kaitlin Allen, Dr. Buys, Dr. Hindle, and Dr. Huckstadt are deploying end of September.

Stay tuned for more updates!

Manu Buys