Rutgers team aims to genetically recreate four-legged creatures from fish eggs

A research team at Rutgers is currently trying to transform fish into four-legged animals in order to solve the genetic mystery of how exactly fish evolved.

When comparing fish with humans, their bone structure actually bears some resemblance to that of humans, said Tetsuya Nakamura, an assistant professor in the Department of Genetics. 

“Our body structure is all based on fish anatomy,” he said.

For instance, the bones on a fish’s front fin could be compared to the fingers, wrist and arm of a human, he said. In the same manner, the back fins of a fish are comparable to a human’s foot. 

Scientists then concluded that over a long period of time, the fins of fish eventually became longer, slowly evolving into limbs that could walk on land. Thomas Wood, a School of Arts and Sciences junior who is also part of the research team, said this evolutionary process was largely driven by genetic mutations.

An organism changes due to mutations that occur during the DNA replication process. Some of these changes can be detrimental, such as stumpy fins for a fish. Sometimes though, a creature could develop a mutation that has advantages over other species, Wood said.

This was the case with the now-extinct Tiktaalik, he said, which is technically considered a fish but had fins that allowed it to venture on land. Over time, Tiktaalik then evolved into other tetrapods, eventually developing into familiar creatures such as cats, dogs and humans.

There are some distinct differences though. Fish have something known as a girdle, which connects their fins to their skulls. Humans, on the other hand, have a neck so they are able to move their heads side to side. It was hypothesized that this was an evolutionary advantage, which is why at some point during the evolution from fish to tetrapod, the bones for the girdle disappeared, Wood said.

The similarities between fish and humans are not only on the surface though. The scientific community recently discovered that the genes found in fish are very similar to the genes of tetrapods, or any four-footed animal, Nakamura said. 

“A couple years ago we were really shocked,” he said. “People thought the genes … were just lost, (which) was a very canonical, old idea.”

It was previously thought that these genes were simply lost during the evolution of fish to tetrapods. It turned out though that the gene expression, or the process in which a gene is made, were almost identical. 

As a result, Nakamura and Wood are currently trying to manipulate the gene expression of fish to further understand their biological and structural makeup. In order to do this, Nakamura said his team would inject parts of the DNA of mice, which were not only conveniently accessible but also very similar to humans, into the genes of different types of fish.

This allows his team to test how the gene functions in fish. He first inserts the mouse gene into a fish egg, then waits several months for the fish to become an adult. Along the way, Nakamura  tracks the shape of these fish to see if there are any differences. To accommodate for the large structural variety of fish in the sea, he said they repeated this process in baby sharks, mudskippers and zebrafish. 

He found in his research that the genetically altered fish were found to have more bones than regular fish, which brings his team closer to the goal of recreating an entire tetrapod from a fish egg. 

Other than the drive for knowledge, the research could also be used to invent medical techniques and tools, Wood said. By understanding the history of a body part structure, doctors can better understand what is happening in a patient and why.

He also said while other spheres, such as politicians, look to the past to determine policies and laws for the future, scientists are more reluctant to look back on history. 

“We’re so keen on … marching forward and forward,” Wood said. 

His hope for the future though, is for his research to one day be used to grow an actual limb, as opposed to a prosthetic. 

“Why not give them an actual arm?” he said.