Gene transfer for targeted modification of salmonid fish metabolism

The reviewed studies addressed the possibility of using gene transfer for correction of L-ascorbic acid biosynthesis and carbohydrate utilization in rainbow trout. Analyses of enzymatic activities in the L-AAB pathway indicated that reasons for the lack of L-AA production can be common in fish and scurvy-prone animals. Rat gulonolactone oxidase cDNA was transferred into trout. Regardless of the fact that rGLO transcription occurred in embryos, neither GLO protein, nor enzyme activity were detected. There was no production of L-AA in transgenic fish raised on vitamin C-free diets or injected with L-gulonolactone. These results indicated that the conditions required for translation or stability of rGLO were not present in trout tissues. To augment carbohydrates utilization, human glucose transporter 1 and rat hexokinase II cDNAs were tested. In the transfected embryos. HK activity, rates of hexose uptake and glucose oxidation were increased. The effect of hGLUT1 on glucose metabolism was greater than that of rHKII. Trout carrying hGLUT1 and rHKII with viral or piscine promoters were created. Though interpretation of the metabolic effects of the transgenes was complicated with mosaicism, a tendency to improved carbohydrate utilization was revealed in some of the transgenic individuals.