Part B | 13.4
400 Part B Tools and Methods in Marine Biotechnology
bility of applying this technique to an aquaculture fish
species, we transferred transgenes with cecropin P1 and
CF-17 into rainbow trout by the sperm-mediated gene
transfer method (Fig. 13.12). A total of nine families of
cecropin P1 transgenic rainbow trout was established
and bred to all male homozygous. Repeated challenge
studies revealed that these transgenic trout exhibited resistance to the bacterial pathogen, Aeromonas salmonicida and the viral pathogen, infectious hematopoietic
necrosis virus (IHNV) [13.103]. Via DNA microarray
and quantitative real-time RT-PCR analyses, the expression of many genes in the innate/adaptive immunity
pathways in transgenic trout was up or downregulated.
This is the first time that a true disease resistant fish is
available for detailed analysis of differential expression
of genes in the innate/adaptive immunity pathways. All
together these results clearly demonstrate the potential
application of transgenic fish technology in producing
fish with more robust resistance to infectious pathogens
for aquaculture.
13.4.2 Enhancement of Somatic Growth
The initial drive of transgenic fish research came from
attempts to increase the production of economically important fish for human consumption. The worldwide
supply of fishery products has traditionally depended
upon commercial harvest of finfish, shellfish, and crustaceans from freshwater and marine water sources. In
recent years, while the worldwide commercial catch of
fish has experienced a sharp reduction, the worldwide
demand for fish products has risen steeply. In order to
cope with the demand for fish products, many countries
have turned to aquaculture. Although aquaculture has
the potential to meet the world demand for fish products, innovative strategies are required to improve its
efficiency. What can transgenic fish technology offer in
this regard?
There are three aspects of fish growth characteristics
that could be improved for aquaculture: i) increasing
the initial growth rate of fry for an early head-start,
ii) enhancing the somatic growth rate in adults to provide a larger market body size, and iii) improving
feed conversion efficiency of fish to achieve effective
utilization of feed. Among these three, enhanced somatic growth rates via manipulation of the GH gene
show considerable promise. Studies conducted by Agellon et al. [13.104] and Paynter and Chen [13.105]
showed that treatment of yearling rainbow trout and
oysters with recombinant rainbow trout GH resulted
in significant growth enhancement. Similar results of
growth enhancement in fish treated with recombinant
GH have been reported by many investigators [13.106–
108]. These results point to the possibility of improving
the somatic growth rate of fish by manipulating fish GH
or its gene.
Zhu et al. [13.109] reported the first successful
transfer of a human GH gene fused to a mouse metallothionein (MT) gene promoter into goldfish and loach.
The F 1 offspring of these transgenic fish grew twice as
large as their non-transgenic siblings. Since then, a similar enhanced growth effect has been observed in GHtransgenic fish (carrying the fish origin GH gene or its
cDNA) of many other species, such as tilapia [13.110,
111], common carp [13.24, 89], catfish [13.16], sea
bream [13.11], and salmon [13.15]. These studies have
shown that the expression of a foreign human or fish GH
gene could result in significant growth enhancement
in P 1; F 1 and F 2 transgenic fish. Additionally, Dunham et al. [13.24] have demonstrated that transgenic
common carp carrying rainbow trout GH transgene
display, consistently in two consecutive generations,
a favorable body shape, better dress-out yield, and better fresher quality compared with non-transgenic fish.
These studies have demonstrated that GH-transgenic
fish may be beneficial to worldwide aquaculture, and
hence may help to alleviate starvation in many economically poor countries by providing more efficient,
cheaper and yet high-quality protein sources. A strain of
fast growing Atlantic salmon (AquAdvantage Salmon),
which was initially developed by Du et al. [13.15]
has been bred by AquaBounty Technologies (Maynard,
MA) for approval by the Food and Drug Administration
(FDA) of USA for commercialization.
13.4.3 Increase of Body Color Variation
in Ornamental Fish
There are two main motives for producing fish with
altered body color: i) to generate novel varieties of
ornamental fish with rare colors for the purpose of rearing as pets, and ii) to use the change of body color
as reporters for detecting environmental changes. The
jellyfish green fluorescence protein (GFP) and several GFP variants driven by tissue-specific promoters
such as the skin-specific keratin gene (krt8) and the
muscle-specific gene (mylz2) are the genes that are
used most for such purposes. Additionally, the melaninconcentrating hormone (MCH) isolated from chum
salmon has also been exploited to generate transgenic
medaka fish with altered body color [13.112]. So far,
researchers have successfully produced several color-
400 Part B Tools and Methods in Marine Biotechnology
bility of applying this technique to an aquaculture fish
species, we transferred transgenes with cecropin P1 and
CF-17 into rainbow trout by the sperm-mediated gene
transfer method (Fig. 13.12). A total of nine families of
cecropin P1 transgenic rainbow trout was established
and bred to all male homozygous. Repeated challenge
studies revealed that these transgenic trout exhibited resistance to the bacterial pathogen, Aeromonas salmonicida and the viral pathogen, infectious hematopoietic
necrosis virus (IHNV) [13.103]. Via DNA microarray
and quantitative real-time RT-PCR analyses, the expression of many genes in the innate/adaptive immunity
pathways in transgenic trout was up or downregulated.
This is the first time that a true disease resistant fish is
available for detailed analysis of differential expression
of genes in the innate/adaptive immunity pathways. All
together these results clearly demonstrate the potential
application of transgenic fish technology in producing
fish with more robust resistance to infectious pathogens
for aquaculture.
13.4.2 Enhancement of Somatic Growth
The initial drive of transgenic fish research came from
attempts to increase the production of economically important fish for human consumption. The worldwide
supply of fishery products has traditionally depended
upon commercial harvest of finfish, shellfish, and crustaceans from freshwater and marine water sources. In
recent years, while the worldwide commercial catch of
fish has experienced a sharp reduction, the worldwide
demand for fish products has risen steeply. In order to
cope with the demand for fish products, many countries
have turned to aquaculture. Although aquaculture has
the potential to meet the world demand for fish products, innovative strategies are required to improve its
efficiency. What can transgenic fish technology offer in
this regard?
There are three aspects of fish growth characteristics
that could be improved for aquaculture: i) increasing
the initial growth rate of fry for an early head-start,
ii) enhancing the somatic growth rate in adults to provide a larger market body size, and iii) improving
feed conversion efficiency of fish to achieve effective
utilization of feed. Among these three, enhanced somatic growth rates via manipulation of the GH gene
show considerable promise. Studies conducted by Agellon et al. [13.104] and Paynter and Chen [13.105]
showed that treatment of yearling rainbow trout and
oysters with recombinant rainbow trout GH resulted
in significant growth enhancement. Similar results of
growth enhancement in fish treated with recombinant
GH have been reported by many investigators [13.106–
108]. These results point to the possibility of improving
the somatic growth rate of fish by manipulating fish GH
or its gene.
Zhu et al. [13.109] reported the first successful
transfer of a human GH gene fused to a mouse metallothionein (MT) gene promoter into goldfish and loach.
The F 1 offspring of these transgenic fish grew twice as
large as their non-transgenic siblings. Since then, a similar enhanced growth effect has been observed in GHtransgenic fish (carrying the fish origin GH gene or its
cDNA) of many other species, such as tilapia [13.110,
111], common carp [13.24, 89], catfish [13.16], sea
bream [13.11], and salmon [13.15]. These studies have
shown that the expression of a foreign human or fish GH
gene could result in significant growth enhancement
in P 1; F 1 and F 2 transgenic fish. Additionally, Dunham et al. [13.24] have demonstrated that transgenic
common carp carrying rainbow trout GH transgene
display, consistently in two consecutive generations,
a favorable body shape, better dress-out yield, and better fresher quality compared with non-transgenic fish.
These studies have demonstrated that GH-transgenic
fish may be beneficial to worldwide aquaculture, and
hence may help to alleviate starvation in many economically poor countries by providing more efficient,
cheaper and yet high-quality protein sources. A strain of
fast growing Atlantic salmon (AquAdvantage Salmon),
which was initially developed by Du et al. [13.15]
has been bred by AquaBounty Technologies (Maynard,
MA) for approval by the Food and Drug Administration
(FDA) of USA for commercialization.
13.4.3 Increase of Body Color Variation
in Ornamental Fish
There are two main motives for producing fish with
altered body color: i) to generate novel varieties of
ornamental fish with rare colors for the purpose of rearing as pets, and ii) to use the change of body color
as reporters for detecting environmental changes. The
jellyfish green fluorescence protein (GFP) and several GFP variants driven by tissue-specific promoters
such as the skin-specific keratin gene (krt8) and the
muscle-specific gene (mylz2) are the genes that are
used most for such purposes. Additionally, the melaninconcentrating hormone (MCH) isolated from chum
salmon has also been exploited to generate transgenic
medaka fish with altered body color [13.112]. So far,
researchers have successfully produced several color-