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Frontiers and Advances in Transgenic Biotechnology of Animals and Fishes
Table 1. Proteins Produced in the Mammary Gland of Transgenic Farm Animals
Protein Production species Therapeutic application
Antithrombin III Goat Genetic heparin resistance
Tissue plasminogen activator Goat Dissolving coronary clots
-A1-antitrypsin Goat and sheep Lung emphysema
Cystic fibrosis
Human clotting factor Sheep Hemophilia A
Human serum albumin Cattle Blood substitute
Blood coagulating factor VIII Pig Haemophilia
Blood coagulating factor IX Pig Haemophilia
Various antibodies Goat
Source: Wilfried and Heiner (2004)
There are several methodologies which can be used for the production of transgenic animals.
Pronuclear microinjection and nuclear transfer (cloning) have been the predominant techniques
used to produce transgenic animals, and they provide benefits for organ transplantation as
well. Over 250,000 people are alive because of the successful allotransplantation of an appropriate
human organ. On average, 75%–90% of patients survive the first year after a transplant,
and the average survival of a patient with a transplanted heart, liver, and kidney is 10–15 years
(Wilfried and Heiner, 2004). This progress in organ transplantation technology has led to an
acute shortage of appropriate organs. Therefore, transgenic animals can help meet the demand
for organ transplantation through cloning technology.
ADVANCES IN DEVELOPING TRANSGENIC FISH
Growth Enhancement of Transgenic Fish
Enhanced growth rates of transgenic fish have the potential to increase production efficiency
by improving feed conversion efficiencies and by reducing production time. The expression
of growth factors such as growth hormones (GH) and insulin-like growth factors (IGFs) has
further resulted in significant growth stimulation in several fish species to date (Martinez et al.,
1999; Nam et al., 2001; Chen et al., 2000). A significant increase in growth rate was observed in
the majority of fish with transgenic GH; for instance, salmon can reach approximately double
the normal body size in half of the normal time (Pitkanen et al., 1999). The mechanism of
growth improvement in transgenic fish is not clear, whether the growth acceleration is a result of
better growth efficiency or a higher rate of food consumption. Some studies have shown more
efficient metabolism in transgenic fish in comparison to their wild counterparts. For example,
transgenic tilapia showed higher protein synthesis and growth rate concomitant with enhanced
glycolysis and increased oxidation of amino acid (Martinez et al., 2000). Transgenic tilapia
carrying carp -actin gene promoter fused to a rainbow trout growth hormone (GH) or insulinlike
growth factor-I (IGF-I) cDNA have been produced by electroporating the transgenes into
newly fertilized tilapia eggs. These transgenic fish not only transmit the transgenes into subsequent
generations but also grow substantially faster than their nontransgenic siblings. These
results point to the potential of improving the growth rate of aquaculture fish by gene transfer
technology involving growth hormone or IGF genes.
Disease and Freeze Resistance
One of the most important goals in the fish industry is to improve the resistance of farmed
fish to pathogens and increase their tolerance to cold water. Preliminary studies show that biotechnology
methods offer new approaches. One approach is to express a lysozyme that has been
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