In the 1980s, gene manipulation studies were producing biotechnology-derived foods. In 1994, the FDA approved the FlavrSavr tomato. Today, 88% of cotton, 97% of soybeans and 85% of corn and 80% of animal feed, produced in the U.S. are genetically modified (GM) or genetically engineered (GE). Its important to note that the livestock feed percentage does not include feed additives, such as enzymes, coloring, antibiotics and amino acids which all can be produced with genetically modified organisms. In the 1980’s the scientific community believed that genetic engineering would prove to be the most effective way to feed, fuel, cloth and heal the world. By the late 1990’s, twenty genetically modified crops were approved for commercial use, sale and consumption (Center for Food Safety, 2013).
As of today, there are not any GE animals approved for human consumption,although this may be changing soon. In 2003 a GE zebra fish was approved for sale solely within pet stores, because it posed no threat to contamination of human food supply. The company AquaBounty genetically altered a salmon, AquAdvantage Salmon (AAS) which allows it to grow four to six times faster. After decades of research, approval of the AquaAdvantage Salmon, or negatively refereed to as frankenfish, is currently in consideration by the FDA.
The first genetically engineered fish was created more that 20 years ago and thirty five species have been genetically engineered since. Fish are used in biotechnology research because their reproductive systems are better suited for genetic engineering, since they lay thousands of eggs featuring external fertilization and embryonic development. These transgenic fish transmit one or more recombinant DNA sequencing, which can be extracted from these eggs (Van Eenennaam, 2005). If one of these GE fish were to lay those eggs in the wild, could they be fertilized and compromise the wild gene pool? Would our native fish population become contaminated like that currently being found in crops by unauthorized GMO seeds? Rare accounts of Atlantic salmon have been known to mate with brown trout and produce hybrid offspring.
Although many concerns about GE fish focus on the risk to human health. This paper will focus on the engineering of the GE salmon, the environmental impact of GE fish, the risk of gene flow, specifically the isolation of the novel gene and precautions taken to prevent the contamination of the wild gene pool.
Gene flow is the movement of alleles from one population to another. Immigration of the novel gene could lead to genetic variants within the wild salmon gene pool. The introduction of the novel gene to the wild gene would reduce the genetic variations between the two, recombining the gene pools and possibly creating a daughter species. If fertilization is able to occur and viable offspring is produced, then the alleles in the GE fish have been able to move into the wild population. This hybridization introgression, or genetic swamping can create homogenization or replace the salmon genotypes; driving the wild salmon to extinction.
Horizontal gene transfer is the movement or direct transfer of genetic material from one species to another without reproduction. Bacteria have proven their ability to exchange genes across special barriers naturally (Ho, Mae, 2000). Genetic engineering creates artificial freeways for genetic material to be transferred from one genome to another, initiating horizontal gene transfer. Although thought to be rare, genes may also flow between species and has been documented in insects, fish, reptiles, and mammals. DNA may transfer from one species to another by viruses.
Salmon are prey for birds, bears, whales, humans, dolphins and other fishes. If these GE fish are eaten by other species and gene transference takes place it could threaten the genetic makeup of the predator. Horizontal gene transfer can lead to detrimental outcomes. It primarily holds the blame for drug and antibiotic resistant pathogens. All species have shown to take foreign DNA into their cells. The design of recombinations are to invade genomes, using artificial constructs that would otherwise not occur in nature. The concern is that these natural genetic barriers are being broken and genetic transfer super highways are being created which then can invade unintended genomes.
Often in genetic engineering the vectors used are viruses and bacteria associated with diseases, because these vectors provide an over expression of the specific gene which they control. This poses a greater risk for transgenic material to be more easily horizontally transferred than non-transgenic material. Transgenic DNA is not as stable as naturally occurring, and has been known to horizontal transfer and not breed true as non-transgenic DNA does. There can be secondary horizontal transfer in cases of seeds and co-cultivation. In studies of these crops, the transgenic material was found in the soil two years after the crop was removed. DNA ingested by predator animals may not be broken down in the gut.
In laboratory mice, transgenic viral DNA was found to be present in the intestinal walls. In pregnant mice, the transgenic viral DNA was found in their fetuses. In some gene therapy research, mammalian cells were invaded and foreign DNA became intertwined with the host, altering the genome (Ho, Mae, 2013). The concern is that if horizontal gene transfer is more likely with GE DNA, that any organisms that consume the AAS will potentially be at risk.
AquaBounty Technologies, the company that engineered the AAS addresses these concerns by ensuring that only triploid females will be produced and they will be raised in raised in land-based facilities only. They believe that this will protect the wild gene pool of other fishes from becoming contaminated (AquaBounty.com, 2013). They ensure that it is impossible for these fish to reproduce. They also wish to gain approval to sell these fish for human consumption. However, in a recent study published by The Royal Society (Oket, Peter, Westley, Moreau, & Fleming, 2013) 4GE salmon were placed in a simulated environment with brown trout and did produce transgenic hybrids. In fact, these offspring proved to express a competitive dominance and outgrew their naturally non transgenic offspring.
Protection of the natural wild gene pool of fishes and other animals should be the primary goal in the determination of experimental regulations and FDA approvals. Some states already have regulations on the raising, sale and transporting of GE animals. Fish are specific, for the reason previously discussed, they lay thousands of eggs. The threat to the wild salmon genome is also a threat to humans. Physical barriers can reduce gene flow. Chemical and genetic barriers may aid in reducing the risk of horizontal gene transfer (Van Eenennaam, 2005). Genetic engineering has brought so many industries into unknown territory. Without prudent federal regulation on the studies and sale of GE organisms, it may only be a matter of time before the artificial constructs created by man , invade man himself.
By: Mechele Linehan