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Sea Creatures 101: Transgenic Fish: GloFish

© Sharon Rorem

There is a hot new fish for aquarium hobbyists. It's called a GloFish. The GloFish name is a trademark of the distributor, Yorktown Technologies which licensed the technology from the National University of Singapore. This fish actually "glows" either red or green. The Glofish didn't start out as a decorative aquarium fish. It was "created" from a common zebra dannio by scientists interested in testing water quality. The first step toward this goal was to "create" a fish that would glow all of the time.

How can a scientist "create" another type of fish? Around 1991, MIT Scientists experimented with inserting a gene called Green Fluorescent Protein (a gene found in jellyfish) into the nucleus of a common zebra dannio fish. This new fish is a "transgenic" fish. The word transgenic means moving a gene from one point to another within the DNA of the same animal or between two different animals. The zebra dannio was chosen because they are easy to care for, grow quickly, and their embryos are transparent which makes observation easy. Another plus is the fact that 75% of their genes are identical to human genes. The process of "planting" a GFP gene into the nucleus takes hours, a great deal of patience, and a steady hand. The nucleus of the zebra dannio is 1/200th the diameter of a human hair. It only had to be done once for the green GloFish. Once the parent fish had been created, when the fish mated with another zebra dannio the dominant "green" gene was carried forward. The process was repeated for the "red" glow, again it only had to be done once. Red Fluorescent Protein (RFP) was taken from a sea anemone and inserted into a zebra dannio nucleus. The fish that grew from that "planting" (the parent fish) was mated with an unaltered zebra dannio. The dominant gene, the "red" one, carried forward and produced red GloFish.

The goal was not to breed transgenic fish for human entertainment. Our waterways are polluted with contaminants that are not easily detected. These fluorescent zebra dannios can be genetically altered even further. Scientists are currently experimenting with adding a "switch" that will trigger color change in the fish. If the water the fish is in has heavy metals in it, the zebra fish will glow red. If the water has oestrogen in it, a type of estrogen that is harmful to fish, the zebra fish will glow green. If the fish doesn't "glow" at all, the water it lives in is safe. The fluorescent zebra fish with a "switch" are not available yet, but fluorescent zebra fish are used by scientists in other ways. For the past ten years or more, scientists have used them to study cellular development and molecular biology. They are also used in cancer and gene therapy.