| Several years ago on a cold February morning, a custodian at the Memorial University Ocean Sciences Centre (OSC; St. John’s, NF) called to tell biochemist Choy Hew that the 200 codfish he was using in his experiments had frozen to death overnight. Hew went to the center and noticed with surprise that flounder continued to swim in the same tank. Why did the flounder survive the low temperatures while the cod did not?
Garth Fletcher, an OSC fish physiologist, suggested that perhaps the flounder contained some kind of “antifreeze molecules”. This proved to be true, and the two researchers became central figures in the structural and functional analysis of several antifreeze proteins (AFPs).
Fletcher, now president of A/F Proteins Canada (St. John’s; www.afprotein.com), concentrates his activities on AFP research and development. Among the potential applications being explored are long-term blood platelet preservation, improvements of cryosurgical techniques, egg and sperm storage, topical cosmetic applications, and the prevention of “freezer burn” in food and transplant organs.
Another avenue being explored is the development of transgenic fish stocks at Aqua Bounty Farms (Fortune Bay, PEI; www.aquabounty.com). In 1981, Hew and Fletcher discussed their work with Arnold Sutterlin, an OSC aquaculturist. Sutterlin wondered if the flounder AFP genes couldn’t be transferred into a more commercially rewarding fish species to protect it from the “superchills” that periodically pass over Canada’s Atlantic coast. Sutterlin eventually succeeded in transferring the AFP gene from winter flounder into Atlantic salmon, giving the salmon limited thermal protection.
Later, the group decided to attack the aquaculture problems from another angle, placing the regulatory sequences of an eel pout AFP gene in front of a growth hormone gene from Chinook salmon. This meant that the salmon would produce growth hormone throughout the year. This “all fish” construct was introduced into Sutterlin’s Atlantic salmon, rainbow trout, and Arctic char, creating the AquAdvantage line of fish stocks. The modified salmon are able to grow at 4–6 times the normal rate and reach market size in less than half of the typical 28 months.
The “all-fish” concept is critical as the researchers recognize the public concern over GMOs. As Sally Goddard, manager of the Newfoundland facility, puts it, “If you ate an ocean pout and a salmon, then you’d have eaten everything that’s in the transgenic.” In addition, because the accelerated metabolism increases the efficiency with which the fish process their food into muscle, the transgenic fish have a lower fat content than unmodified fish.
But the rest of the scientific community does not necessarily share the rosy views of the Newfoundland group. Robert Devlin, a researcher at the West Vancouver lab of Fisheries and Oceans Canada, has concerns over the viability of such “superfish”. His group found that mature domesticated trout selected for enhanced growth were equal in size to normal trout genetically modified with a salmon growth hormone gene. Additionally, unlike their domesticated cousins, the modified fish died before sexual maturation and showed physical abnormalities. Added to concerns over the possible contamination of wild stocks by the transgenic fish, these results have led Devlin to argue against the development of GM fish.
Sources
Devlin, R. H. et al. Nature 2000, 409, 781–782.
Fletcher, G. L.; Goddard, S. V.; Wu, Y. L. CHEMTECH 1999, 29, 17–28.
Hew, C. L.; Fletcher, G. Chem. Ind. London 1997, 8, 311–314.
Reichhardt, T. Nature 2000, 406, 10–12. |
