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Transgenic coho salmon expressing growth hormone had enlarged heads, reduced viability, and accelerated development of their life cycle.

Manipulated Organism: Coho salmon (Oncorhynchus kisutch).

Inserted Transgenes: Type I salmon growth hormone gene. In the first study (Devlin et al., 1995), transgene expression was controlled with the anti-freeze protein (AFP) promoter from ocean pout (Zoarces americanus). In the second study (Devlin et al., 2004), transgene expression was controlled with the metallothionein-B (MTH) promoter from sockeye salmon (Oncorhynchus nerka).

Goal of These Studies: Study the growth and development of transgenic salmon.

Results of This Study:
  • In the first study, transgenic larvae were paler and had a distinct green color, whereas the non-GM offspring displayed the typical brown color of coho salmon larvae. The transgenic larvae also had enlarged heads relative to their body size, and this abnormality became more exaggerated with age. Several transgenic individuals had difficulty feeding and breathing because of excessive growth in their jaw and gill covering. By the time the transgenic salmon were one year old, many had died.

  • In the second study a different promoter (MTH) was used with the same growth hormone transgene. Although similar symptoms were observed (e.g., enlarged heads), the abnormalities were more moderate. The transgenic fish showed accelerated development throughout their life cycle, including:

    • The GM eggs hatched two days earlier than the non-GM cohort (4 versus 6 days).

    • By their first birthday the GM salmon had reached a size more typical of two-year-old non-GM salmon raised in the hatchery. The one-year-old GM fish had also passed from the parr to smolt stage of development, while this transformation took two years for the non-GM salmon. (In the wild, coho salmon become smolt before migrating to the ocean, and this transformation includes changes in color.)

    • The GM salmon became sexually mature at two years of age, whereas the non-GM salmon required three years to reach this stage of development.

Additional Comments: "The growth-accelerated transgenic coho salmon are distinct from nontransgenic salmon in many respects, including early hatch timing, shortened life cycles, precocious development of life history characteristics, and altered morphology, physiology, behaviour, and viability" (p. 627-8).

Source: Devlin, R. H., T. Y. Yesaki, E. M. Donaldson, and C.-L. Hew (1995). "Transmission and Phenotypic Effects of an Antifreeze/GH Gene Construct in Coho Salmon (Oncorhynchus kisutch)," Aquaculture vol. 137, pp. 161-9.

Devlin, R. H., C. A. Biagi, T. Y. Yesaki (2004). "Growth, Viability, and Genetic Characteristics of GH Transgenic Coho Salmon Strains," Aquaculture vol. 236, pp. 607-32.

Author Affiliations: Fisheries and Oceans Canada, West Vancouver; University of Toronto, Canada.

Funding: Canadian Biotechnology Strategy.

Product Status: Not on the market as of 2009.

Copyright 2009 The Nature Institute.

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