In the transgenic freak show department:
A decade-long effort by a University of Rhode Island scientist to develop transgenic rainbow trout with enhanced muscle growth has resulted in fish with what have been described as six-pack abs and muscular shoulders.
Assuming successful safety assessments and regulatory approval, the development of more muscular trout could boost commercial aquaculture because aquaculturists could grow larger fish without increasing the amount of food the fish are fed.
According to Terry Bradley, a URI professor of fisheries and aquaculture, his exploration into the inhibition of myostatin, a protein that slows muscle growth, has obtained "stunning results" in the last two years, with trout growing 15 to 20 percent more muscle mass than standard fish.
Unlike fish, the number of muscle fibers in mammals is limited after birth, says Bradley. In fish, however, since muscle fiber numbers increase throughout their lifespan, there was no telling whether inhibiting myostatin would cause an increase in muscle growth.
"Belgian blue cattle have a natural mutation in myostatin causing a 20 to 25 percent increase in muscle mass, and mice overexpressing myostatin exhibit a two-fold increase in skeletal muscle mass. But fish have a very different mechanism of muscle growth than mammals, so we weren't certain it was going to work," Bradley said.
Turns out that with a bit of time it did work. Bradley and his team spent 500 hours injecting 20,000 rainbow trout eggs with various DNA types designed to inhibit myostatin. Of the eggs that hatched, 300 carried the gene that led to increased muscle growth. After two years, most exhibited "body-builder" physiques with "six-pack abs" even though fish lack standard abdominal muscles.
The increased musculature throughout their body included a prominent dorsal hump that made them look like they had muscular shoulders. The fish displayed no change in behavior compared to their natural counterparts.
The first generation of transgenic trout were subsequently spawned, and offspring carrying the gene in all of their muscle cells have been produced.
Now, studies are under way to determine if the fish grow at a faster rate as well.
The implication of the research are two fold, says Bradley. "The results have significant implications for commercial aquaculture and provide completely novel information on the mechanisms of fish growth."
It also allows for comparisons between the mechanisms of growth of muscle in mammals versus fish, and it could shed light on muscle wasting diseases in humans.
Bradley will continue to study the fish to learn if the new gene affects any other genes, and to determine if new husbandry practices will aid in the raising of the trout.
Source: University of Rhode Island