Open Research Europe presents Christopher Emerling, author of ‘Genomic evidence for the parallel regression of melatonin synthesis and signaling pathways in placental mammals’, in this month’s research spotlight. Read on to find out more about his research.  

Can you briefly tell us about your research?  

Several kinds of vertebrates (animals with backbones), ranging from crocodilians, whales, sloths, and pangolins, lack a pineal gland, the organ that produces the nighttime hormone melatonin, an important molecule for signaling environmental darkness to the body. 

We investigated this possibility by examining the genes responsible for synthesizing and signaling the presence of melatonin in all types of reportedly pineal-less vertebrates. We found evidence that these genes are ‘broken’ in several groups of mammals that lack a pineal gland.

What inspired you to investigate this subject and write this article?  

I am interested in how life evolves over long periods of time (macroevolution), and particularly regressive evolution, which refers to the loss of or diminishment of traits and characteristics. For example, limbless snakes might have descended from lizards with legs, the toothless anteaters and pangolins likely had ancestors with teeth, and certain subterranean mammals have lost much of the functionality of their eyes. Why, how, and how often this happens fascinates me. A great way to study this is to look at how the genes underlying these traits (e.g., legs, teeth, eyes) can erode into dysfunctional “pseudogenes” over time. 

I read that the xenarthrans (sloths, armadillos, anteaters), a group of mammals I often study, lacked a pineal gland which inspired further research. After further research, I discovered two genes required for synthesizing melatonin in the pineal gland and two genes important for signaling the presence of melatonin to the rest of the body. When I was working on xenarthran genomes in early 2016, I immediately looked for these genes in sloths, armadillos, and anteaters. I was surprised to find these genes were present but broken pseudogenes. This seemed quite bizarre given the importance of melatonin in so many forms of life, including bacteria, plants, fish, mammals and humans.  It took some time to carry out the rest of the work, but given how strange the implications are, it is now one of my favorite projects. 

What were the outcomes of your research?  

Previous research suggests melatonin has existed in organisms for billions of years and impacts all sorts of functions in the biology of mammals. Our results, that dozens of species of mammals appear not to be able to synthesize or respond to melatonin, raise many questions for future research. The biggest question for me is, “How can these mammals function normally without using melatonin?”. When traits are lost during the evolution of life, we think they are no longer useful to the organism. This could be due to a shift in their environmental pressures, or that another trait has taken over those functions. This leads to another pair of essential questions:   

• “What environmental pressures would lead to the loss of melatonin functionality?”  

• “What physiological traits have taken over melatonin’s previous role?”   

Though we noticed some similarities between certain groups of mammals that lost these genes (e.g., manatees and whales are fully aquatic; pangolins and anteaters are highly adapted to eating ants and termites; mole-rats live underground), the biggest commonality seemed to be linked to living in habitats that are relatively stable in temperature, but this is just our best guess. There certainly could be better explanations out there, and some might be unique to each group of mammals. Either way, we are very interested to see what others find out. 

Why is open research important to you and your co-authors? 

I speak for myself and some of my co-authors by saying that it is crucial for research to be available for public access. When research is behind paywalls, it prevents the general public from accessing knowledge, should they be so inclined to view the primary sources.  

Furthermore, it is not inherently obvious to some people how the review process is carried out, and transparent review allows them to have further insights into how science goes from the desks of scientists to its final published form.  

It’s also important because scientific publications are often unavailable to researchers at universities and colleges that typically can’t afford access to journals behind a paywall. I currently work at a college, making it difficult for me to do research without being able to read research performed by my colleagues. Making publications open and available creates a better scientific ecosystem, allowing for more comprehensive research and the cross-pollination of ideas. 

What motivated you to publish with Open Research Europe? 

My co-author, Frédéric Delsuc at the Université de Montpellier, is currently working on a European Research Council funded project (https://www.convergeant-project.com) and introduced me to the platform. I had been lamenting about the time it takes for papers to get published in traditional journals, and he proposed that Open Research Europe might be a satisfying option. This, paired with the desire to provide research in an open access format and my longstanding curiosity about the transparent review process, made me eager to publish on Open Research Europe. 

I was particularly pleased with the publication process and how rapidly our work was made available. Knowing that it was published and had journal-appropriate formatting made Open Research Europe more attractive to me than a preprint server. Furthermore, not having to wait on an editor to compile every individual review, but rather getting to see them in almost real time, was a nice touch. This allowed us to start thinking about revisions sooner. 

What are your next steps? 

As far as the melatonin story goes, we have no immediate plans to work on this further, but we are certainly looking forward to reading what other researchers contribute to the topic. 

Frédéric Delsuc and I will continue to work on our mutually favorite mammals (e.g., sloths, anteaters, pangolins, and others), studying how they’ve evolved over millions of years by looking at various aspects of their biology. Our co-authors Mark Springer and John Gatesy will undoubtedly work on other projects with us due to our overlapping interests. There’s a lot of work to do, and a lot of exciting things in the pipeline. 

Want to find out more? Read the article here.