MS, Biology, Friedrich-Alexander University
PhD, Biology, Max Planck Institute for Developmental Biology
How animals adapt to their environment and the resilience mechanisms they evolved to survive is the driving force behind the research of Nicolas Rohner, PhD. Spending most of his childhood outside hiking and mushroom hunting in the forests of Germany, Rohner quickly became captivated by the ‘endless forms most beautiful’, as evolving organisms were described by Darwin in The Origin of Species.
His interest in this diversity of life steered Rohner toward a career in science. In 2002, Rohner earned a BS in biology and an MS in genetics at Friedrich-Alexander-University (FAU) in Erlangen, Germany. He earned his PhD at the Max Planck Institute for Developmental Biology in Tübingen, Germany in the lab of nobel laureate Christiane Nüsslein-Volhard. Rohner completed his postdoctoral training in the lab of developmental biologist Cliff Tabin, PhD, at Harvard Medical School, where he focused primarily on the genetics of the cavefish Astyanax mexicanus.
In the Mexican cavefish – descendants of river fish swept into dark underground caves by floods thousands of years ago – Rohner found an ideal model system in which to study adaptation and resilience. Due to the complete darkness in caves, cavefish rely entirely on outside food sources, brought in by seasonal flooding during the rainy season. As such, cavefish have evolved a feasting and fasting cycle, allowing them to store impressive amounts of body fat and starve for months with ease. Over the years, Rohner has developed a system to compare fish from the river to the fish who live in caves. It gives scientists a rare look at what happens when species adapt to extreme nutritional challenges.
Inspired in part by his cavefish studies, Rohner has become an intermittent faster, eating just one meal a day — usually dinner. But he’s no ascetic. When he does eat, it’s with pleasure in mind. “I’m half-French. I love to cook. I love good food and I love good wine. So when I get a chance I feast as well.”
In his lab, Rohner’s team is studying extreme metabolic adaptation and its implication for metabolic diseases. “There are many examples for this in nature: hibernating animals, migrating birds, snakes that eat large amounts of food, store excess energy as fat and then starve for extended periods of time. But for them, it doesn’t have any negative consequences,” Rohner says. For example, some migrating birds develop a fatty liver, but unlike humans, it doesn’t develop inflammation. For almost every problem you study, it seems that evolution has already found a solution.”
Shedding light on this phenomenon, Rohner and his collaborators reported that Mexican cavefish developed high blood sugar and insulin resistance, without any noticeable health effects, in a newsworthy March 2018 paper in Nature. Subsequently, they have shown that while cavefish have excessive visceral fat, they actually have fewer signs of inflammation compared to their river-dwelling kin, who have an active immune system to fight off parasites. In contrast, these cavefish have adapted to an environment with few to no parasites without having auto-inflammatory diseases common in species living under similar environmental conditions. This work was published in Nature Ecology and Evolution in July 2020. Earlier, Rohner and his colleagues reported in the Proceedings of the National Academy of Sciences that cavefish share a mutation with humans that make cavefish binge eat to store up fat for times when food is scarce. Interestingly enough, in humans the same mutation causes people to overeat as well.
“We’ve just scratched the surface,” says Rohner about his research. “We’re really interested in learning more about how cavefish become resilient to all these traits that are considered metabolic dysfunction in other systems. There’s still a lot to discover in that area.”