Impact of Genetically Engineered Fish in Maine

By Eric D. Anderson, Assistant Professor of Biochemistry, Microbiology & Molecular Biology, University of Maine

SUMMARY

Genetically modified organisms (GMO), once found only in scientific laboratories, are now in shopping markets. On the horizon are GMO fish. These fish, in part, have fueled debate ranging from whether it is ethical and safe to produce and consume the organism, to matters of agricultural economics. The Maine legislature will soon consider LD-0713, which would require labeling of GMOs. Here I will outline some basic scientific facts about GMO fish that may be useful during the debate.

Two issues need to be discussed in assessing the risk of utilizing transgenic animals for food. The first is to determine whether there is a legitimate need for the genetically engineered organism. Does the new trait confer a significant economic or quality advantage over the non-transgenic animal to outweigh any possible risk that might ensue? The second consideration is whether expression of the transgene trait poses any risk to human health or the environment.

Within this framework, the term "transgenic food" needs to be defined. First, a transgene is any gene that has been intentionally and artificially inserted into the DNA of another organism. There are two fundamentally different types of genetically modified animals: those organisms that can transmit the transgene to their offspring (known as germline carriers) and those that express the transgene in their body tissues but cannot pass that trait to their offspring (known as somatic carriers).

Efforts to genetically engineer fish have centered on two goals: altering the growth rate and food conversion efficiency of fish, and reducing losses by increased resistance to disease. Accelerated growth of fish has been demonstrated by germline expression of growth hormones and antifreeze proteins. These hormones and proteins enable fish to grow faster, larger, and at lower temperatures. By contrast, disease resistance approaches have focused on somatic expression of so-called "DNA vaccines." These compounds elicit an immune response against a pathogen the animal has not yet encountered.

In addressing the issue of legitimate need for these fish, it is not clear whether there is a demonstrated need for farmed fish with genetically engineered traits that speed growth or decreases the amount of food required to attain a marketable size. But to the contrary, there is a clear need for DNA vaccines for the control of fish diseases in aquaculture. DNA vaccines have many benefits: they will increase the health and well-being of farmed fish, reduce losses due to lethal pathogens, reduce the potential for amplification of diseases at the farm site, and reduce the potential for transfer of diseases between wild and farmed fish.

There are no clear human health risks associated with expression of fish growth hormones, antifreeze genes or DNA vaccines. However, concerns have been raised about other genes which accompany the desirable genes. The genetic engineering process for germline cells requires co-expression of what scientists call a selectable marker. In this case, the marker is usually an antibiotic resistance gene. These antibiotic resistance genes are not known to pose a health risk when the organism is consumed. However, concern has been raised whether there are risks associated with possible transfer of these antibiotic resistance genes to microbes. The chances of such transfer in aquatic environments is not known. Thus, at present, it is difficult to assess whether the use of germline transgenic fish is justified. However, new methods are now available that eliminate the transfer of antibiotic resistance genes to engineered organisms.

Another issue involves environmental concerns regarding escape of farmed genetically engineered fish containing traits for accelerated growth or increased food conversion. The risks posed by these organisms are similar to those of any introduced species. The short-term risks include domination of native fish for food and habitat, dilution of the wild fish gene pool by interbreeding, disruption of the ecosystem, and potential creation of new pests. The long-term risks are unpredictable.

Two general methods could be used to reduce the risks. The first is to farm fish in land-based, bio-contained facilities which eliminate the possibility of escape. The second method is to sterilize the fish. However, complete sterilization of an entire stock of fish in field trials has not been successful. Because of these drawbacks, farming of genetically engineered fish with accelerated growth rate or increased conversion efficiency may not be desirable.

There are no obvious environmental risks associated with the use of somatically expressed DNA vaccines in aquaculture. The worst case scenario would be escape of the vaccinated fish and re-population of habitats in which native fish populations had been diminished due to disease. Generation of new recombinant pathogens may be possible, but this risk is not unique to DNA vaccinated fish.

For further information, contact:

Eric D. Anderson, Assistant Professor

Biochemistry, Microbiology & Molecular Biology

University of Maine

Phone: 581-2807 or Email: eandersn@maine.maine.edu

or

Irving Kornfield, Professor

School of Marine Sciences

University of Maine

Phone: 581-2548 or Email: irvk@maine.maine.edu

The University of Maine provides education on genetics and related topics as part of its Land Grant mission. Through courses and research with faculty members, students gain a thorough understanding of the science of genetics as well as its applications. Graduates qualify for jobs in the growing biotechnology industry and apply their skills in a variety of other occupations. As part of the university’s research mission, UMaine scientists focus on basic genetic processes as well as those specifically relevant to agriculture, forestry, fisheries, wildlife and human health. Faculty collaborate with researchers at The Jackson Laboratory and the Maine Medical Research Center as well as federal laboratories and other universities.

Dr. Eric Anderson’s Dr. Eric Anderson’s research pursuits include the evolution and molecular epidemiology of viral pathogens of salmon and trout, and the development of efficacious vaccines for the control of viral diseases of fish.

 Dr. Irv Kornfield is a professor of zoology at the University of Maine with a PhD in ecology and evolution. His research interests are population biology and molecular systematics. Research is supported by the National Science Foundation, UM/UNH Sea Grant, the State of Maine (Warden Service), and the Maine Aquaculture Innovation Center.