October 16th 2016: Today, we are deploying to resume our work with the Weddell seals on the Antarctic sea ice in McMurdo Sound. We will once again collect plasma, tissue samples, and swabs (for microbiome analysis). In our lab in McMurdo, we will process blood and tissue samples to isolate RNA and protein and work on establishing cell cultures.
Many people have asked us whether we obtained the data we were aiming for after our previous deployment. The short answer is: it is a work in progress. For most of the experiments we are running, additional samples are required before we can finalize our studies and publish our findings. As I am making my way from Boston via Los Angeles and Auckland to Christchurch where we will board a military flight to the Pegasus Runway on the Ross Ice Shelf, I do have a moment or two to reflect back on the work we have done over the past year.
Our B-267 team first deployed in the fall of 2015 (September 30th-December 7th) to McMurdo, Antarctica. Over a 10-week span our field team collected various samples from live animal biopsies (skin, blubber, muscle, blood), as well as fresh placental tissue (post-partum) and necropsies of naturally deceased animals. During necropsy procedures, we collected tissue from various organs and organ systems: heart (all chambers), kidney, spleen, lung, liver, brain (cortex, cerebellum), muscle (pectoralis, L. dorsi), aqueous humor, aorta (arch, thoracic, abdominal), and other arteries (pulmonary, renal, carotid, splenic, mesenteric). These tissues were designated for several experimental endpoints, including gene expression analysis, protein activity analyses, and immunohistochemistry. Thus far, in ongoing experiments (that will need to repeated in samples we aim to collect this season), we have focused on assessing the activity and expression (mRNA and protein) level of soluble guanylate cyclase (sGC), a key enzyme in regulation of vascular function. We also collected fresh blood from adults and pups. We are currently measuring cGMP levels (the metabolite generated by sGC) in plasma and sGC activity in platelets. Of note, our experimental setup is designed to be comparative: sGC enzyme activity in Weddell seal samples is being compared with sGC enzyme activity in samples collected from mice, rats, and sheep.
In ancillary studies, we are studying the Weddell Seal lipidome and microbiome. Weddell Seals have occupied a unique, extremely cold niche on the Antarctic shelf ice, in part, by evolving a thick blubber layer and associated metabolic pathways that rapidly store and mobilize fats from this tissue. We are interested in understanding the mechanisms by which stored maternal fat is mobilized in Weddell moms during lactation and conversely, how fats from mothers’ milk is rapidly deposited in the developing blubber of the pup. We speculate that in the seal, as opposed to the human condition, selective pressure have generated metabolic adaptations to prevent bloodstream deposition of oxidized lipoproteins in the vessel wall and subsequent triggering of innate inflammatory signaling pathways during these periods of high lipid flux through the bloodstream. Dr. Michael Fitzgerald and Dr. Slim Sassi at MGH are analyzing serum samples from Weddell seals and comparing them to samples from a number of other mammals, including humans. The sera are fractionated using fast protein liquid chromatography (FPLC) and the fractions corresponding to human VLDL, LDL and HDL are analyzed for the cholesterol content. Early results suggest that female Weddell seals have very high circulating cholesterols levels, in the range of person with homozygous familial hypercholesterolemia who would be prone to heart attacks in their teens. In contrast, the seals do not seem bothered by these high circulating cholesterols levels. Our preliminary data justifies ongoing efforts to take advantage of the emerging Weddell seal genome to identify potential genetic evolution in the lipid metabolism pathways that regulate circulating cholesterol levels.
Over the course of our previous deployment, we also collected swabs for microbiome analysis collected from pups and adults. The characterization of 97 oral, nasal, fecal and skin microbiomes from adult Weddell seals and pups was evaluated via 16S rRNA gene sequencing in collaboration with Dr. Nadim Ajami and his colleagues at the Alkek Center for Metagenomics and Microbiome Research at Baylor College of Medicine. Preliminary results identified intriguing clues as to the bacterial diversity characterizing the Weddell seal microbiome. In addition to collecting additional swabs to confirm our data this year, we will also have our own microbiome studied as we travel across the globe.
Stay tuned for updates on the second chapter of our Antarctic adventure, both on our blog and the B-267 Instagram. Also, check out the blog of Dr. Mark Seefeldt, my roommate from last season. He deployed earlier this year (during Winfly) and has already made his way back home to the US.
Yup: Science is still fun!