What killed the harbor seals?

My time as a Ph.D. student in the Vega-Thurber lab has come to an end. Completing my dissertation was a very exciting and relieving moment in my life.  To add to this excitement, just a few days after my latest paper from my dissertation was published in the Journal PeerJ. This paper was an extension of the work that I talked about on a previous blog.


Celebrating the completion of my P.h.D

Celebrating the completion of my P.h.D

In my last paper, I looked at the bacteria and viruses from a group of seven young harbor seals that died from some unknown brain disease. When veterinarians performed a necropsy (the animal version of an autopsy), it appeared that these animals were infected with viruses. Although, when we used high-throughput sequencing (sequencing of large amounts of DNA or RNA) to identify a virus we did not find any. The lack of viruses in my results was very surprising as well as disheartening. See I wanted my research to revolve around characterizing viruses, but given that, I could not find any viruses this inhibited my grand research plans.

This situation is very common in research; our hypotheses are not always correct and we often get negative results. It’s one of the aspects that makes the work of a scientist challenging, but it also keeps us thinking and generating new ideas.

My next step was to refocus my question and approach. If a virus did not kill this group of animals something else did. Now I had a new question to answer. What killed the harbor seals? To answer this, I examined the genes of the seven harbor seals. I used a sequencing technique that is known as transcriptomics or RNA-sequencing. This technique is a high-throughput sequencing approach looking at all the genes in a sample. In my case, I was examining the genes in each of the seven seals that died from the mysterious brain disease.

I then analyzed the genes of the harbor seals using computer programs, statistics, and biological principles (bioinformatics). To my surprise, all these animals had high levels of genes related to fatty acid metabolism. Unexpected results are also a common occurrence in research. I initially believed that these animals died from a virus, but my results were suggesting that they likely died from a metabolic disease!

What does high levels of fatty acids in the brain signify?  Generally, fatty acids are important for building cells and providing energy to cells. Fatty acid gene activity typically takes place in fat and the liver cells, and large production of these gene types may indicate a metabolic disease. Things that trigger high fatty acid production includes poor nutrition intake or exposure to toxins. So, we think that these animals either did not absorb proper nutrients or encountered a toxin that caused high fatty acid metabolism production in their brains, which may have led to their death.

So now that we know that fatty acid metabolism dysfunction can occur in the brains of marine mammals we can begin to monitor these genes in other marine mammals. We can look for the same fatty acid genes that we found in our study in other animals. This will help us better understand this disease and hopefully prevent the deaths of other animals. Interestingly, when I began this research question, I envisioned the final results of my study very differently. I didn’t expect to examine marine mammal genes and metabolic pathways, but research has a mind of its own and leads us to unexpected and exciting findings.

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