Transgenic expression of growth hormone in coho salmon led to a narrower
body, more red muscle mass, and smaller white muscle fibers.
Coho salmon (Oncorhynchus kisutch).
Type I salmon growth hormone gene.
Goal of This Study:
Compare the muscle anatomy, physiology, and gene expression of transgenic
salmon with non-GM relatives of similar size. Because the transgenic
salmon grow more rapidly, the size-matched non-GM salmon were one year
Results of This Study:
Despite having comparable total body weight and length, the transgenic
fish had narrower bodies. The cross-sectional area of the transgenic fish
at mid-length was 75% the area of the non-GM fish. Additionally, the
abdominal wall of the GM fish was only half as thick.
There are two types of skeletal muscle in animals: red and white,
specialized for sustained versus rapid activity, respectively. The amount
of red muscle in the tail of the GM fish was twice that in the non-GM fish
(2% vs. 1% red, p < 0.01).
The white fibers of the GM fish were half as wide, indicating that
muscle development had changed to emphasize the proliferation of new
cells (hyperplasia) over the growth of existing cells (hypertrophy).
The specific activity of phosphofructokinase (PFK), a key enzyme in
the utilization of glucose and critical to muscle function, was over
three times higher in the transgenic fish (p < 0.01).
"In conclusion, increased growth rates, caused by transgenesis, in coho
salmon have resulted in changes to muscle architecture consistent with
increased rates of hyperplasia [cell proliferation]. This identifies
a meat quality effect of growth rate that can be considered in future
studies. Changes in levels of the muscle enzymes PFK and Cytox suggest
effects on metabolism that can also lead to changes in meat quality due
to postmortality effects" (p. 949).
Hill, J. A., A. Kiessling, and R. H. Devlin (2000). "Coho Salmon
(Oncorhynchus kisutch) Transgenic for a Growth Hormone Gene Construct
Exhibit Increased Rates of Muscle Hyperplasia and Detectable Levels of
Differential Gene Expression," Canadian Journal of Fisheries and Aquatic
Sciences vol. 57, pp. 939-50.
Fisheries and Oceans Canada, West Vancouver; Swedish University of
Fisheries and Oceans Canada; Swedish University of Agricultural Sciences.
Not on the market as of 2009.
Copyright 2009 The Nature