Evolutionary lessons from an ancient fish
Evolution and gars – freshwater fish with toothy snouts – are so intricately intertwined that one MSU researcher created a vanity license plate, highlighting his dedication to this research – “Garwin.”
At the Board of Trustees’ Aug. 31 meeting, Ingo Braasch, MSU assistant professor of integrative biology, shared even more connections between man and fish in his presentation, “Of Fish and Men.”
“Basically, my research shows what fish can tell us about the genetic basis of our own human evolution, development and disease,” Braasch said. “In many cases, fish like gar or zebrafish can serve as models for human disease research for conditions such as cleft palate for example.”
As it turns out, the genetic underpinnings of cleft palate have striking similarities in fish and people, and the deformity can be traced to the same genes in both groups. Using genetic tools, scientists can work to fix cleft palate in fish and then, in turn, apply the genetic framework to human medicine.
This approach to use “biomedical” fish models has applications across many human functions. For example, unraveling the platyfish genome is shedding light on the formation of skin cancer, which in turn helps understand melanoma in humans. Researchers around the world are using numerous additional fish systems to investigate specific human diseases.
“When you look at an image of zebrafish embryo that’s about one day old, it looks quite similar to a human embryo that’s almost a month old; their overall shapes and the location of the heads and eyes and ears are virtually identical,” Braasch said. “As they develop, of course, they look quite different. However, this tells us that fish and human development are similar enough that fish can be used to investigate many aspects of the human condition.”
Garfish has been called a “bridge species,” as its genome is similar to that of both zebrafish and human, a discovery in which Braasch led. This correlation means that scientists are able to identify a disease-associated genetic region in humans, locate the corresponding region in the spotted gar genome and then investigate the appropriate location in the genomes of zebrafish or other fish models to potentially understand disease development.
“We are using gar to further improve comparisons of humans to zebrafish and thereby helping to make zebrafish and other fish species even better model systems for disease research,” Braasch said. “By studying gar and zebrafish side by side, we also hope to answer many more evolutionary questions about the origin of vertebrate genomes and their biology, including our own ancestry.”
Gars, found from Central America to Michigan, evolve slowly and have kept more ancestral elements in their genome than other fish. This means that along with serving as a bridge species to humans, gars also are great connectors to the past.
“Charles Darwin coined the phrase ‘living fossil,’” Braasch said. “Studying gars and other so-called ‘ancient fishes’ exemplify this because the living species resembles long-extinct relatives from the fossil record.”
Listening to Braasch discuss his research and remembering his car’s tag, it sounds like he has a lot on his plate.