Would it surprise you to know that some of the small, striped fish in your local pet store are also a fundamental model organism in research labs across the world? Danio rerio, or “Zebrafish”, are a common sight in freshwater aquariums. Zebrafish are natively found in freshwater habitats in South Asia, where they grow to approximately 1 inch long and display 5 uniform stripes running along the side of their bodies. In an aquarium, they are easy to maintain and do well with other species of fish.
But this is all just the tip of the iceberg when it comes to the humble Zebrafish. Scientific interest started in the 1970s when Dr. George Streisinger from the University of Oregon pioneered their use as a model organism. Zebrafish were among the first vertebrate animals to be successfully cloned, have a fully sequenced genome, and are easy to examine throughout their entire developmental cycle. In addition, Zebrafish have remarkable abilities to regenerate after injury – this includes repairing heart, neuron, and other cells, including the ability to repair and regrow entire finns. Because of this, Zebrafish have become an essential organism for research in developmental biology, genetics, cancer research, environmental science, neurobiology, and more.
One of the most important developments within Zebrafish research has been the creation of transgenic strains. Transgenic, or genetically modified, organisms are those that have been altered through recombinant DNA technology. This involves combining the DNA from different organisms or inserting foreign DNA into the Zebrafish genome. Today, transgenic organisms are used for both research and commercial applications. For example, genetically modified crops have been developed to be more nutritious, require less water, or grow in warmer environments. Transgenic Zebrafish are used to examine the overexpression of genes during early development or the progression of cancer. In addition, fluorescent genes can be inserted to make it easier for a scientist to track proteins, cells, or entire organs within the animals. In 2003, the first commercially available transgenic organism was revealed… the GloFish™. These are genetically modified Zebrafish that display bright fluorescent proteins throughout their bodies, giving the fish a vibrant red, green, blue, orange, or purple color.
While research use of transgenic organisms has produced countless scientific advances, the use of animals is not without controversy. Many animal rights activists believe that this research is immoral or unethical, and there are concerns about translating research from a model organism into humans. This is an important consideration for research into disease, genetics, and other issues related to human health. In addition, there is concern about transgenic organisms escaping into the wild and the impact that could have on an ecosystem. Unfortunately, this concern was recently highlighted by the discovery of fluorescent Zebrafish in creeks in southeastern Brazil. Despite a ban on the sale of GloFish in Brazil, the country is one of the largest producers of the fish in the world. Scientists expect that some of the fish escaped from an aquaculture farm into the wild and are now thriving due to a lack of natural predators. The long-term impact will not be known for some time, but it is possible that they could seriously disrupt the ecosystem. Alternatively, it is possible that the bright colors of the GloFish will make them an easy target for larger fish which will minimize the environmental impact. Either way, this discovery highlights the potential impact of invasive species and the need for care to be taken with transgenic organisms.
To read more about the Zebrafish in Brazil check out this recent article from Science. For more information on transgenic organisms, check out our recent blogs on c. elegans in the laboratory and the detection of genetically modified foods. These both include wonderful experiment ideas for the classroom laboratory!