Sexually Dimorphic Growth Stimulation in a Strain of Growth Hormone Transgenic Coho Salmon (Oncorhynchus kisutch) (original) (raw)
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Aquaculture, 2012
Several different transgenic growth hormone (GH) gene constructs have been used to obtain accelerated growth in salmonids. However, there have been limited direct comparisons of these constructs in terms of the ability to achieve maximal growth in fish. We examined the effect of promoter type (sockeye salmon metallothionein-B or histone 3) fused to a growth hormone-1 coding region from the same species (OnMTGH1 and OnH3GH1 constructs respectively) on growth and plasma growth hormone (GH) and insulin-like growth factor-I (IGF-I) in multiple strains of GH transgenic coho salmon (Oncorhynchus kisutch). Salmon transgenic for the OnMTGH1 construct had consistently greater overall weight than those containing the OnH3GH1 construct, although both groups possessed greatly accelerated growth over non-transgenic fish. However, there were strong strain effects, where some OnH3GH1 strains had similar weight to OnMTGH1 strains while others did not. Triploidy diminished growth acceleration and decreased condition factors in both a fast growing MT strain and slower growing H3 strain. Plasma GH levels did not correlate to weight in transgenic strains, and all but one transgenic strain had plasma GH levels similar to equal sized non-transgenic fish. In contrast, plasma IGF-I content correlated well to size in transgenic strains. The mechanism by which accelerated growth in transgenic fish is obtained appears to be due in part to an upregulation of GH action through increased circulating IGF-I levels, and promoter-type appears to influence potential for growth.
Aquaculture, 2000
Transgenic coho salmon containing a growth hormone GH gene construct have been examined for their hormone levels and ability to osmoregulate in sea water. Relative to their Ž . smaller nontransgenic siblings age controls , GH-transgenic coho precociously develop external phenotypes and hypo-osmoregulatory ability typical of smolts. Specific growth rates of the transgenic coho were approximately 2.7-fold higher than older nontransgenic animals of similar size, and 1.7-fold higher than their nontransgenic siblings. GH levels were increased dramatically Ž . 19.3-to 32.1-fold relative to size control salmon, but IGF-I levels were only modestly affected, being slightly enhanced in one experiment and slightly reduced in another. Insulin levels in transgenic animals did not differ from size controls, but were higher than nontransgenic siblings, and thyroxine levels in transgenic animals were intermediate between levels found in size and age controls. The homeostatic controls of, and interactions among, these hormones are discussed with respect to their effects on growth and osmoregulation. q
Proceedings of The National Academy of Sciences, 2009
Domestication has been extensively used in agricultural animals to modify phenotypes such as growth rate. More recently, transgenesis of growth factor genes [primarily growth hormone (GH)] has also been explored as a rapid approach to accelerating performance of agricultural species. Growth rates of many fishes respond dramatically to GH gene transgenesis, whereas genetic engineering of domestic mammalian livestock has resulted in relatively modest gains. The most dramatic effects of GH transgenesis in fish have been seen in relatively wild strains that have undergone little or no selection for enhanced growth, whereas genetic modification of livestock necessarily has been performed in highly domesticated strains that already possess very rapid growth. Such fast-growing domesticates may be refractory to further stimulation if the same regulatory pathways are being exploited by both genetic approaches. By directly comparing gene expression in wild-type, domestic, and GH transgenic strains of coho salmon, we have found that domestication and GH transgenesis are modifying similar genetic pathways. Genes in many different physiological pathways show modified expression in domestic and GH transgenic strains relative to wild-type, but effects are strongly correlated. Genes specifically involved in growth regulation (IGF1, GHR, IGF-II, THR) are also concordantly regulated in domestic and transgenic fish, and both strains show elevated levels of circulating IGF1. Muscle expression of GH in nontransgenic strains was found to be elevated in domesticated fish relative to wild type, providing a possible mechanism for growth enhancement. These data have implications for genetic improvement of existing domesticated species and risk assessment and regulation of emerging transgenic strains.
Endocrine effects of growth hormone overexpression in transgenic coho salmon
General and Comparative Endocrinology, 2008
Non-transgenic (wild-type) coho salmon (Oncorhynchus kisutch), growth hormone (GH) transgenic salmon (with highly elevated growth rates), and GH transgenic salmon pair fed a non-transgenic ration level (and thus growing at the non-transgenic rate) were examined for plasma hormone concentrations, and liver, muscle, hypothalamus, telencephalon, and pituitary mRNA levels. GH transgenic salmon exhibited increased plasma GH levels, and enhanced liver, muscle and hypothalamic GH mRNA levels. Insulin-like growth factor-I (IGF-I) in plasma, and growth hormone receptor (GHR) and IGF-I mRNA levels in liver and muscle, were higher in fully fed transgenic than non-transgenic fish. GHR mRNA levels in transgenic fish were unaffected by ration-restriction, whereas plasma GH was increased and plasma IGF-I and liver IGF-I mRNA were decreased to wild-type levels. These data reveal that strong nutritional modulation of IGF-I production remains even in the presence of constitutive ectopic GH expression in these transgenic fish. Liver GHR membrane protein levels were not different from controls, whereas, in muscle, GHR levels were elevated approximately 5-fold in transgenic fish. Paracrine stimulation of IGF-I by ectopic GH production in non-pituitary tissues is suggested by increased basal cartilage sulphation observed in the transgenic salmon. Levels of mRNA for growth hormone-releasing hormone (GHRH) and cholecystokinin (CCK) did not differ between groups. Despite its role in appetite stimulation, neuropeptide Y (NPY) mRNA was not found to be elevated in transgenic groups.
PLoS ONE, 2014
Should growth hormone (GH) transgenic Atlantic salmon escape, there may be the potential for ecological and genetic impacts on wild populations. This study compared the developmental rate and respiratory metabolism of GH transgenic and non-transgenic full sibling Atlantic salmon during early ontogeny; a life history period of intense selection that may provide critical insight into the fitness consequences of escaped transgenics. Transgenesis did not affect the routine oxygen consumption of eyed embryos, newly hatched larvae or first-feeding juveniles. Moreover, the timing of early life history events was similar, with transgenic fish hatching less than one day earlier, on average, than their non-transgenic siblings. As the start of exogenous feeding neared, however, transgenic fish were somewhat developmentally behind, having more unused yolk and being slightly smaller than their non-transgenic siblings. Although such differences were found between transgenic and non-transgenic siblings, family differences were more important in explaining phenotypic variation. These findings suggest that biologically significant differences in fitness-related traits between GH transgenic and non-transgenic Atlantic salmon were less than family differences during the earliest life stages. The implications of these results are discussed in light of the ecological risk assessment of genetically modified animals.
General and Comparative Endocrinology, 2012
To examine the relative growth, endocrine, and gene expression effects of growth hormone (GH) transgenesis vs. GH protein treatment, wild-type non-transgenic and GH transgenic coho salmon were treated with a sustained-release formulation of recombinant bovine GH (bGH; Posilac™). Fish size, specific growth rate (SGR), and condition factor (CF) were monitored for 14 weeks, after which endocrine parameters were measured. Transgenic fish had much higher growth, SGR and CF than non-transgenic fish, and bGH injection significantly increased weight and SGR in non-transgenic but not transgenic fish. Plasma salmon GH concentrations decreased with bGH treatment in non-transgenic but not in transgenic fish where levels were similar to controls. Higher GH mRNA levels were detected in transgenic muscle and liver but no differences were observed in GH receptor (GHR) mRNA levels. In non-transgenic pituitary, GH and GHR mRNA levels per mg pituitary decreased with bGH dose to levels seen in transgenic salmon. Plasma IGF-I was elevated with bGH dose only in non-transgenic fish, while transgenic fish maintained an elevated level of IGF-I with or without bGH treatment. A similar trend was seen for liver IGF-I mRNA levels. Thus, bGH treatment increased fish growth and influenced feedback on endocrine parameters in nontransgenic but not in transgenic fish. A lack of further growth stimulation of GH transgenic fish suggests that these fish are experiencing maximal growth stimulation via GH pathways.
Growth, viability and genetic characteristics of GH transgenic coho salmon strains
Aquaculture, 2004
Transgenic coho salmon strains containing an all-salmon growth hormone (GH) gene construct (OnMTGH1) have been examined. The transgene utilized is comprised of the metallothionein-B promoter driving the expression of the type-I growth hormone gene from sockeye salmon. Transgene DNA is integrated into the salmon genome, but is transmitted at low frequency from founder transgenic animals consistent with late integration following microinjection resulting in mosaic animals, whereas subsequent generations transmit transgene DNA as a stable Mendelian trait. Different families established from separate founder animals yield lines with unique growth characteristics suggesting important site-of-integration effects on transgene expression. Growth enhancement of transgenic salmon is initiated early, with advanced hatch timing but occurring also throughout the life history, particularly during the early phase in fresh water. GH transgenic fish showed precocious smoltification and onset of sexual maturation, but approximately normal adult body size, indicating that compression of the normal coho salmon life history is occurring. The viability of diploid GH transgenic salmon ranges from reductions to greater than that of controls among strains, and triploid transgenic animals had normal viability relative to diploid transgenic salmon. Triploid transgenic salmon display a reduction in growth rate relative to transgenic diploids, but are still significantly growth enhanced compared with nontransgenic controls. The distinct phenotypic characteristics of GH transgenic families suggest that evaluation for aquaculture and for risk assessments requires examination of strains on a case-by-case basis. Furthermore, strong effects of size at maturity in culture conditions were observed for nontransgenic wild strain coho salmon which were not apparent in GH transgenic salmon,
Smolt development in growth hormone transgenic Atlantic salmon
Aquaculture, 1998
. Growth hormone transgenic Atlantic salmon Salmo salar produced using a gene construct Ž . Ž comprised of an antifreeze protein AFP gene promoter from ocean pout Macrozoarces . Ž. Ž americanus and the growth hormone GH gene from chinook salmon Oncorhynchus . tshawytscha were used for this study of smolt development. An F generation of these transgenic 2 salmon was initiated in November 1995 using milt from a transgenic F male and eggs from a ) Corresponding author 1 For the Department of Fisheries and Oceans, Government of Canada. 0044-8486r98r$ -see front matter Crown Copyright q 1998 Published by Elsevier Science B.V. Ž . PII: S 0 0 4 4 -8 4 8 6 9 8 0 0 3 4 8 -2 ( ) R.L. Saunders et al.r Aquaculture 168 1998 177-193 178 It appears that GH transgenic Atlantic salmon can be reared under temperature and photoperiod regimes which optimize growth, but which would inhibit normal smolt development and post-smolt performance of non-transgenic salmon. Crown
Aquaculture Research, 1999
In salmonids, growth hormone (GH) stimulates growth, appetite and the ability to compete for food. This study tested the hypothesis that increased GH levels in GH-transgenic coho salmon Oncorhynchus kisutch (Walbaum) increase competitive ability through higher feeding motivation. The transgenic strain of salmon used contained a gene construct consisting of the sockeye metallothionein-B promoter fused to the type 1 growth gene coding region. The transgenic animals (mean size = 250 g) were F 1 individuals. In six consecutive feeding trials, the intake of contested food pellets by size-matched pairs consisting of one control (1 year older nontransgenic coho salmon) and one GH-transgenic coho salmon was compared. Pellets were provided sequentially until neither ®sh took three consecutive pellets; the identity of the ®sh taking each pellet was noted. Calculated on the three ®rst pellets offered at each feeding trial, the transgenic coho salmon consumed 2.5 times more contested pellets than the controls, supporting the hypothesis that GH transgenesis increases the ability to compete for food. Overall, the transgenic ®sh consumed 2.9 times more pellets that the non-transgenic controls, indicating a high feeding motivation of the transgenic ®sh throughout the feeding trials. It appears that GH transgenesis and GH treatments can induce similar changes in the feeding behaviour of salmonids. Depending on how transgenic and wild individuals differ in other ®tness-related characters, escaped GH transgenic ®sh may compete successfully with native ®sh in the wild.