Effects of domestication and growth hormone ...

9 downloads 0 Views 1MB Size Report
and †USDA-ARS, Hagerman Fish Culture Experiment Station, 3059-F National Fish ...... Rise, M. L., S. E. Douglas, D. Sakhrani, J. Williams, K. V. Ewart, M.
Effects of domestication and growth hormone transgenesis on mRNA profiles in rainbow trout (Oncorhynchus mykiss)1 R. H. Devlin,*2 D. Sakhrani,* S. White,* and K. Overturf† *Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC, Canada, V7V 1N6; and †USDA-ARS, Hagerman Fish Culture Experiment Station, 3059-F National Fish Hatchery Road, Hagerman, ID 83332

ABSTRACT: Growth rate can be genetically modified in many vertebrates by domestication and selection and more recently by transgenesis overexpressing growth factor genes [e.g., growth hormone (GH)]. Although the phenotypic end consequence is similar, it is currently not clear whether the same modifications to physiological pathways are occurring in both genetic processes or to what extent they may interact when combined. To investigate these questions, microarray analysis has been used to assess levels of mRNA in liver of wild-type and growth-modified strains of rainbow trout (Oncorhynchus mykiss). This species has been used as a model because nondomesticated wild strains are available as comparators to assess genetic and physiological changes that have arisen both from domestication and from GH transgenesis. The analysis examined pure wild-type and pure domesticated strains as well as 2 different GH transgenes (with markedly different growth effects) both in pure wild and in wild × domesticated hybrid backgrounds. Liver mRNA showed highly concordant changes (Pearson correlations; r > 0.828; P < 0.001) in levels in domesticated and GH transgenic fish, relative to wildtype, for both up- and downregulated genes. Further-

more, among domesticated, transgenic, and their hybrid genotypes, a strong correlation (P < 0.001) was found between growth rate and the number of genes affected (r = 0.761 for downregulated mRNA and r = 0.942 for upregulated mRNA) or between growth rate and mRNA levels relative to wild-type (r = 0.931 for downregulated mRNA and r = 0.928 for upregulated mRNA). One GH transgenic strain was found to affect growth and mRNA levels similar to domestication whereas effects of the other GH transgenic strain were much stronger. For both GH transgenes, a hybrid domesticated × wild background influenced growth rate and mRNA levels to only a small extent relative to the transgenes in a pure wildtype genetic background. Functional analysis found that genes involved in immune function, carbohydrate metabolism, detoxification, transcription regulation, growth regulation, and lipid metabolism were affected in common by domestication and GH transgenesis. The common responses of mRNAs in domesticated and GH transgenic strains is consistent with the GH pathway or its downstream effects being upregulated in domesticated animals during their modification from wild-type growth rates.

Key words: domestication, gene expression, growth hormone, microarray, rainbow trout, transgenic © 2013 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2013.91:5247–5258 doi:10.2527/jas2013-6612 INTRODUCTION

1The

authors gratefully acknowledge support from the Canadian Regulatory System for Biotechnology. The authors appreciate the availability of cGRASP genomic resources for salmonids from the laboratories of Ben Koop (University of Victoria) and Willie Davidson (Simon Fraser University). The present research was supported by Canadian Regulatory System for Biotechnology funds provided to RHD. 2Corresponding author: [email protected] Received April 18, 2013. Accepted September 3, 2013.

Enhancement of growth in agricultural animals has been a major consequence of domestication and remains a fundamental objective of many animal agricultural breeding programs. Differences in growth rate between wild and domesticated strains involves upregulation of the growth hormone/insulin-like growth factor (GH/ IGF) axis (Weiler et al., 1998; Giachetto et al., 2004; Bunter et al., 2005; Tymchuk et al., 2009b) and is genetically complex (Le Rouzic et al., 2008; Rubin et al., 2010;

5247 Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5248

Devlin et al.

Wringe et al., 2010; Amaral et al., 2011). Growth hormone (GH) transgenesis can also elevate growth rate, but effects have been relatively modest in avian and mammalian agricultural species (Pursel et al., 1989, 1997; Rexroad et al., 1991; Rozycki et al., 1999) compared to dramatic effects in fish (Devlin et al., 2006). Transcript levels are altered by domestication or GH transgenesis and are associated with multiple metabolic, structural, and regulatory pathways (Rise et al., 2006; Tymchuk et al., 2009a; Debes et al., 2012; Drew et al., 2012; Li et al., 2012). Growth hormone transgenes can have reduced effect in fast-growing domesticated trout compared to wild-type (Devlin et al., 2001b), and genetic background influences growth rates in GH transgenic mice (Siewerdt et al., 2000). These data suggest that pathways (e.g., GH/ IGF-1 axis) modified during domestication may be similar to that for GH transgenesis, which could influence effects of transgenesis in growth-selected genetic backgrounds (Pursel et al., 1989). In coho salmon, a strong correlation for differences in mRNA levels relative to wild-type has been found for domesticated and GH transgenic strains (Devlin et al., 2009; Overturf et al., 2010). The objective of this study was to assess hepatic mRNA levels in wild-type, domesticated, GH transgenic, and transgenic × domesticated hybrid rainbow trout to further our understanding of gene regulatory relationships acting to modify growth in these 2 distinct approaches to growth modification. MATERIALS AND METHODS Fish were reared and handled in accordance with Canadian Council of Animal Care guidelines and was authorized by Fisheries and Oceans Canada’s Pacific Region Animal Care committee. Fish Strains and Fish Culture To examine the effects of domesticated and GH transgenic genotypes and their hybrids relative to wildtype, 4 strains of rainbow trout have been used to generate the 6 experimental groups used in this study. The reference wild strain [both genomes wild-type (W/W)] was propagated from parental trout collected from nature from Pennask Lake, British Columbia. (Nomenclature in this study uses a slash between the 2 haploid genome abbreviations present within a diploid genotype.) The domesticated trout [both genomes domesticated (D/D)] are derived from the Campbell Lake strain, which is a growth-enhanced commercial strain available in British Columbia that has been under selection for greater than 30 yr and grows much faster than wild-type [see specific growth rates for weight (SGR-W) in Table 1]. Effects of 2 GH transgenes (T1 and T2) have also been studied.

These transgenic fish were originally generated by the insertion of the OnMTGH1 growth hormone gene construct (Devlin et al., 2001b, 2004) into a Pennask Lake trout wild genetic background. The transgenic strains are the fifth generation from original synthesis and have been propagated at each generation by repeated backcrossing to wild-caught Pennask Lake trout to prevent domestication effects arising in the strains due to culture in aquarium environments. Note that the genotype designation of T1 or T2 represents the respective GH transgene inserted at single loci in a haploid wild genome, and hence T1/W and T2/W represent genotypes of these transgenes within wild-type diploid animals. Transgenic individuals possessing both a wild and a domesticated genome (i.e., domesticated × wild hybrid background) plus a GH transgene were also generated in 2 family groups, grown separately for each transgenic strain (designated T1/D and T2/D). Fish were reared at Fisheries and Oceans Canada’s laboratory in West Vancouver, which houses aquatic facilities specifically designed to prevent the introduction of transgenic fish into the wild. Crosses were performed to generate the genotypes described below and, following rearing in the hatchery in Heath trays, were transferred to 200 L tanks at the first feeding stage on August 2, 2007. All rearing occurred in 10 ± 1°C aerated well water at a density less than 5 kg/m3. Fish were fed stageappropriate artificial salmon diets (Skretting Canada Ltd., Vancouver, Canada) to satiety 3 times per d. Before sampling, fish were euthanized in 100 mg/L MS-222 (Syndel Laboratories Ltd., Nanaimo, Canada) buffered with 200 mg/L sodium bicarbonate. Specific growth rates [SGR-W and specific growth rates for length (SGR-L)] were calculated as specific growth rate (SGR) = (lnX2 – lnX1)/d,

Table 1. Weight (W), length (L), specific growth rates for weight (SGR-W), and specific growth rates for length (SGR-L) for fish (n = 5) used in the microarray experiment. Mean ± SE Genotype1 W/W+1 D/D T1/W T1/D T2/W T2/D

W, g 39.02 ± 1.97a 33.70 ± 2.26a 36.30 ± 2.33a 41.62 ± 5.64a 118.46 ± 8.82b 145.32 ± 2.86c

SGR-W 0.27 ± 0.11a 1.64 ± 0.05b 1.72 ± 0.13b 1.73 ± 0.11b 2.45 ± 0.09c 2.42 ± 0.09c

L, cm 15.88 ± 0.23a 13.58 ± 0.30bc 14.48 ± 0.35ac 14.08 ± 0.71c 20.92 ± 0.52d 22.54 ± 0.23d

SGR-L 0.19 ± 0.03a 0.54 ± 0.02b 0.53 ± 0.03b 0.48 ± 0.05b,c 0.59 ± 0.04b 0.65 ± 0.02b,d

a–dWithin a column, means without a common superscript differ (P < 0.05; ANOVA followed by Holm-Sidak post hoc test) 1W/W+1 = wild type trout 1 yr older (total 556 d) than all other groups (size matched at 191 d of age); D/D = pure domesticated strain; T1/W = T1 transgene in a pure wild genetic background; T1/D = T1 transgene in a wild × domesticated hybrid genetic background; T2/W = T2 transgene in a pure wild genetic background. T2/D, T2 transgene in a wild × domesticated hybrid genetic background.

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

Domestication vs. transgenic effects on mRNA

in which X2 is the weight or length of the fish at time 2 and X1 is the weight or length at time 1. Body size at specific ages differs among some of the genotypes examined due to genetically programmed differences in growth rate. Therefore, to minimize ontogenetic and body-size effects on mRNA levels (R. Devlin, unpublished data), for the microarray experiments size-matched individuals from the various strains were used that experienced the same rearing conditions (season, water temperature, and photoperiod). For example, for the wild strain, which grows much slower than the other groups, it was necessary to use trout from the previous year’s wild brood (W/W+1; wild-type 1 yr older) to obtain individuals of a similar size. The sampling date (February 8, 2008; age 191 d for all groups except W/W+1) was determined when the T1 transgenic (T1/W; pure wild genetic background), domestic (D/D), and wild × domesticated hybrids with the T1 transgene (T1/D) groups were the same body size as the W/W+1 group. This allowed examination of mRNA levels in wild, domesticated, GH transgenic, and transgenic × domestic hybrid trout at the same relative developmental stage. Due to the very rapid growth of the T2 transgenic families (T2/W and T2/D genotypes), no sizematched fish were available for analysis at sampling time, and therefore fish representative of the average for each of these groups were used. At the sampling date, weights of fish of the same genotype differed between the 2 families, suggesting either tank effects or genetic backgrounds differed (P < 0.05) between the 2 families for each strain genotype (W/W, W/D, D/D, T/W, T/D, and W/W+1). However, these differences were much smaller than the strain effects under study (e.g., domestication and GH transgenesis). To assess the current physiological state of the fish at the time of sampling (rather than their life-time growth response), growth rates were determined for the 21-d period immediately before tissue collection. Specific growth rates were determined for Passive Integrated Transponder tagged fish from each group (each of the 2 D/D families were combined) by assessing their growth rates over the 21-d period. For each group, 5 fish were selected for microarray analysis such that their SGR did not differ from the SGR measured for all the fish in that same group. Several fish in the W/W+1 group had negative SGR and were not included in the pool of fish considered for analysis. The weight, length, SGR-W, and SGR-L of fish used in the microarray experiment are shown in Table 1.

5249

Molecular Biology Ribonucleic acid purification and microarrays were performed as described (Devlin et al., 2009) except that the Consortium on Genomics Resources for All Salmon Project (cGRASP; http://web.uvic.ca/grasp/) 16K chip (provided by the laboratory of Dr. Ben Koop, University of Victoria, Victoria, Canada) was used (Koop et al., 2008). Levels of mRNAs from each fish (n = 5 per group; 6 genotypic groups; 30 slides total) were analyzed on a single slide using a pooled reference design, where the reference RNA pool comprised equal amounts of RNA from all wild-type samples. Experimental RNA samples from individual fish were cohybridized with the reference pool to generate normalized levels of signal (e.g., sample Cy5 signal/reference pool Cy3 signal). Each cDNA feature and individual were analyzed by ANOVA followed by Student Newman Keuls post hoc test, using GeneSpring (Agilent, Mississauga, Canada) software. All microarray data for the current experiment has been submitted to the National Center for Biotechnology Information Gene Expression Omnibus (GEO; www.ncbi.nlm.nih.gov/ geo) and are available under GEO accession number GSE47562. Functional analyses of genes followed (Devlin et al., 2009) and were assigned to the following categories: apoptosis, cell cycle function, cell and/ or tissue structure and development, generation of precursor metabolites and energy, homeostasis, lipid metabolism, carbohydrate metabolism, protein metabolism, nucleotide metabolism, protein synthesis, proteolysis, signaling, transcription, translation, response to stimulus, and transport. To examine the correlation between mRNA levels and growth rate, 2 approaches were undertaken. First, concordance indices were generated as the number of genes showing the same response (i.e., increased mRNA level in both or reduced in both) for each of all possible strain pairs, expressed as a proportion of the total number of genes showing a significant (P < 0.05) difference from wild-type. Concordance indices were calculated both for all significant (P < 0.05) genes as well as for genes that differed specifically between the gene pair being examined. Second for all strain pairs, ratios of mRNA levels were calculated as the ratio of the average fold difference in mRNA level relative to wild-type for either upregulated or downregulated genes. For both of these approaches, Pearson correlation analysis (Sigmastat, San Jose, CA) was performed to compare the relationship of strain SGR (weight) vs. either concordance index or average mRNA level (relative to wild-type). To examine the relationship of mRNA levels between 2 groups among genes, Pearson correlations were performed (Sigmastat). Correlation coefficients

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5250

Devlin et al.

Figure 1. Weight (mean ± SE) of fish among different wild, domesticated, and growth hormone transgenic genotypes. Lowercase letters indicate significant differences (P < 0.05) among groups for within family 1 (T1 strain crosses) whereas capital letters indicate differences for groups within family 2 (T2 strain crosses). Genotype identifiers: W/W = wild; W/D = wild × domestic F1 hybrid; D/D = pure domesticated; T/W = transgenic strains in a wild background; T/D = transgenic strains in a wild × domestic hybrid background; W/W+1 = wild strain 1 yr older than other groups to allow size matching. Note that W/W and W/D fish are presented for comparative purposes and their molecular analysis is not presented here. Age of measurement was 188 d post–first feeding (pff) for all genotypes except W/W+1, which were 1 yr older.

were calculated on nontransformed data, however data are graphed and regression lines shown for log transformed data. All correlations were highly different from zero (e.g., P < 0.001) RESULTS To assess changes in levels of mRNAs relative to wild-type arising from domestication vs. GH transgenic genetic modifications in rainbow trout, several strains of trout and their hybrids were grown under culture conditions. A domesticated and 2 GH transgenic strains of rainbow trout all showed greater growth relative to wild-type trout and wild × domesticated hybrids over a 6-mo growth period, and resulted in fish of very different sizes among strains at the same age (Fig. 1). Domesticated trout were 5.3-fold to 5.4-fold heavier than wildtype fish in the 2 families whereas domesticated × wild hybrid trout were intermediate in size between wild and domestic strains (R. Devlin, unpublished data), consistent with the additive nature of the genetic differences observed for another domesticated strain relative to wildtype (Tymchuk and Devlin, 2005). One transgenic strain (T1) stimulated body weight (relative to wild-type) at a level similar to that seen in the domesticated strain (5.4fold) whereas the other transgenic strain (T2) stimulated growth to a much greater extent (27.6-fold heavier than wild-type). For the specific fish used in the microarray analysis, SGR-W for domesticated trout (D/D) were

greater (6.1-fold) than seen for wild-type (W/W+1; Table 1). Specific growth rates for weight for transgenic trout were also higher than wild-type: strain T1 causes growth stimulation similar to that seen for the domesticated strain (6.4-fold greater than wild-type) whereas strain T2 showed much stronger (9.1-fold) growth rate stimulation. For both transgenic strains, combining domesticated and transgenic genotypes together (i.e., transgenics in a hybrid domesticated × wild background) did not yield significantly faster-growing fish than seen for the transgene acting in a pure wild genetic background (Fig. 1; Table 1). Thus, a gradation of growth stimulation is seen among strains with the rank order W/W < W/D < D/D = T1/W = T1/D < T2/W = T2/D. Using the cGRASP 16K microarray chip, levels of liver mRNA were examined from wild (W/W+1), domesticated (D/D), strain T1 transgenic (T1/W), strain T2 transgenic (T2/W), and T1/D and T2/D transgenic × domestic hybrid genotypes. All samples were examined relative to a reference pool of wild-type mRNA. The cDNA features on the microarray used for analysis (n = 8,919) were those in the 20 to 100 percentile range of signal intensity and were expressed in all 5 individuals within a group. Of these, 517 (5.8%) were found to differ significantly in at least 1 group relative to wildtype (Table 2). Overall (i.e., both up- and downregulated genes considered together), the number and proportion of genes that differed from wild-type (range from 277 to 412) shows (top row, Table 2) the same rank relationships among groups as seen for growth rates among strains described above. Furthermore, the number of affected genes among other genotype pairs is correlated with level of growth stimulation, such that fewer genes differ in mRNA level when genotypes that are growing at similar rates are compared. The proportions of genes showing up- vs. downregulation relative to wild-type were relatively equal among all the genotypes compared (diagonal, Table 2). However, the proportion of genes showing similar responses (i.e., either up in both strains or down in both strains) varied considerably between strain pairs, with the greatest concordance (82.4–94.6%) seen when comparing transgenic genotypes amongst themselves or with domesticated salmon (Table 2, below diagonal). A more varied relationship (60.1–63.1% concordance or less) was seen when comparisons were made between wild-type and any transgenic or domesticated genotype. Regression analysis of concordance of mRNA levels in a strain pair (proportion either up in both or down in both) vs. the ratio of growth rates between the same strains, compared across all possible pairs of strains, shows a significant (P < 0.001) negative correlation (Fig. 2A) both when all significant genes are examined (r = –0.942) or when only genes differing between the pairs (r = –0.761) are examined.

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

Domestication vs. transgenic effects on mRNA

5251

Table 2. Numbers of genes differentially regulated, proportion and concordance of up- vs. downregulated genes, and correlation coefficients (r) for mRNA levels among pairs of wild, domestic, and growth hormone transgenic genotypes. Above diagonal: values indicate number and proportion (in parentheses) of genes differing between strain pairs (determined by Student Newman Keuls post hoc test) among all genes (n = 517) differing in any strain pair comparison. Diagonal: percentage of genes showing upregulation in a strain relative to wild type. Below diagonal: proportion of genes showing same response (up or down) between strain pairs (concordance). Values in parentheses indicate Pearson’s linear correlation coefficients (r) for mRNA levels for each strain pair (number of genes for correlations for each genotype pair shown above diagonal and ranges from 277 to 412). All correlations were significant (P < 0.001). Genotype1 W/W+1 54.9 W/W+1 D/D T1/W T1/D T2/W T2/D

0.631 (0.251) 0.625 (0.194) 0.605 (0.167) 0.617 (0.232) 0.609 (0.253)

D/D 277 (0.536) 56.3 0.828 (0.742) 0.870 (0.819) 0.828 (0.646) 0.824 (0.716)

T1/W 310 (0.600) 101 (0.195) 45.1 0.915 (0.960) 0.911 (0.901) 0.888 (0.892)

T1/D 342 (0.662) 104 (0.201) 36 (0.070) 43.1 0.880 (0.888) 0.872 (0.901)

T2/W 394 (0.762) 251 (0.485) 146 (0.282) 149 (0.288) 48.9 0.946 (0.962)

T2/D 412 (0.797) 259 (0.501) 188 (0.364) 177 (0.342) 72 (0.139) 49.7

1W/W+1

= wild type trout 1 yr older (total 556 d) than all other groups (size matched at 191 d of age); D/D = pure domesticated strain; T1/W = T1 transgene in a pure wild genetic background; T1/D = T1 transgene in a wild/ domesticated hybrid genetic background; T2/W = T2 transgene in a pure wild genetic background; T2/D = T2 transgene in a wild/domesticated hybrid genetic background.

Examining average changes in mRNA levels for significant genes showed a similar response among strains as seen for numbers of genes affected. Correlation of ratios of mRNA levels between strains vs. the ratio of growth rates seen for the same strains showed significant relationships (P < 0.0001) for both upregulated (r = 0.928) and downregulated (r = –0.931) genes when all significant genes were examined (Fig. 2B) and when only genes significant to specific pairs were compared (not shown). Similarly, a heat map display of mRNA levels patterns among genotypes shows a transition of differences from wild-type to domesticated to transgenic and transgenic × domesticated hybrid genotypes (with T2 also appearing stronger than T1) for both upregulated and downregulated genes (Fig. 3). Hierarchical clustering of genotypes found that all wild individuals and all domesticated individuals clustered by genotype, as did transgenic genotypes as a

Figure 2. Relationship between mRNA levels and growth among strains. A. Relationship of strain specific growth rates for weight (SGR-W) ratios vs. genes showing a concordant response among strain pairs (i.e., proportion either up in both or down in both), using all significant genes (closed diamonds) as well as genes differing only between specific pairs (open squares). B. Relationship of strain growth ratios (SGR-W) vs. average intensity of mRNA levels for up- and downregulated genes among strain pairs. Correlation coefficients (r) are shown.

collective group. Among transgenic fish as a group, there was a strong trend (i.e., 1 exception among 20 fish examined) to clustering of genotypes by their tendency to influence growth (e.g., T2 vs. T1), and this relationship was not strongly influenced by wild vs. wild × domesticated hybrid genetic backgrounds. The microarray patterns appeared to follow similar relationships among genotypes as was found for growth responses. Correlation analysis of the significant gene list was performed to examine whether concordant or discordant responses existed among genotypes. Correlations of wild genotype against other genotypes were, although significant, quite low (r < 0.253 for W/W compared to all genotypes; Table 2 below diagonal in parentheses) and

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5252

Devlin et al.

showed variation primarily in the domestic or transgenic axes rather than the wild axis (see example: W/W vs. D/D correlation; Fig. 4A). This is expected as mRNA levels were assessed relative to a wild reference pool, and therefore only interindividual genetic and environmental variation would be represented in W/W (y) axis whereas interstrain variation is represented in the D/D (x) axis. Correlations among domesticated, T1 or T2 pairs of genotypes and their hybrids were all much greater (r = 0.646 to 0.962; Table 2). For example, a strong correlation exists between D/D vs. T1/W genotypes (Fig. 4B) and between the 2 transgenic genotypes (e.g., T2/W vs. T1/W; Fig. 4C). Furthermore, little effect of domesticated vs. wild genetic backgrounds was apparent in these analyses (e.g., see strong correlation for T1/W vs. T1/D; Fig. 4D). Functional analysis identified major changes in mRNA levels in GH transgenic and domesticated salmon relative to wild-type for genes involved in response to stimulus, cell and/or tissue structure and development, generation of precursor metabolites, lipid metabolism, transport, transcription, and cell cycle function as well as genes involved with nucleotide and protein metabolism. For genes in transgenic, domesticated, or transgenic × domesticated hybrid fish with a greater than 2-fold difference from wild-type (n = 161), 89 could be assigned to functions (Fig. 5) and 102 were found to differ in 2 or more genotypes (57 with known functions). Of these, several genes showed greater than a 2-fold increase or decrease in the domesticated strain and at least 1 transgenic strain and were associated with diverse functions (Table 3). The genes with reduced mRNA levels were involved in ribosome biosynthesis and osmotic balance whereas genes with elevated RNA levels were involved in immune function, carbohydrate metabolism, detoxification, transcription regulation, growth regulation, and lipid metabolism. Two of 3 genes with functions related to lipid metabolism were strongly upregulated: Gastrulation-specific protein G12 (involved in regulation of acetyl-CoA carboxylase) mRNA was elevated 6.4- to 10.3-fold over wild-type levels whereas acetyl-CoA desaturase mRNA was upregulated 7.9- to 19.0-fold. DISCUSSION The present study has identified a strong correlation between levels of liver mRNA among domesticated and GH transgenic trout. Upregulated and downregulated mRNA were found to change concordantly, suggesting alterations to overall physiological processes in domesticated and GH transgenic trout are similarly modified. A similar proportion of genes were found to be elevated or decreased in the same direction by domestication or GH transgenesis relative to wild-type, suggesting that changes in specific mRNA are not being strongly influenced by a

Figure 3. Heat map showing relationship between mRNA level and strain [wild-type (W/W), domesticated (D/D), transgenic in a wild background (T1/W and T2/W), and transgenic × domesticated hybrids (T1/D and T2/D)]. Levels of mRNAs are represented by colored bars: yellow (unaffected), red (elevated), and blue (reduced). Each column represents an individual animal. Clustered relationships at the top of the figure represent similarities among strains based on patterns of mRNA levels whereas clustering in the vertical axis represents commonality of mRNA level pattern of separate genes. See online version for figure in color.

global regulation of mRNA levels (e.g., mRNA:rRNA ratios). Therefore, for these domesticated and GH transgenic strains with a common phenotype (i.e., enhanced growth), it appears that many of the same genes are involved and are modified in similar ways by both types of genetic modification from wild-type.

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

Domestication vs. transgenic effects on mRNA

5253

Figure 4. Correlations of mRNA levels (relative to wild-type) among example strain pairs. A. Wild-type (W/W) vs. domesticated (D/D). B. Transgene T1 in a wild background (T1/W) vs. domesticated (D/D). C. Transgene T2 in a wild background (T2/W) vs. transgene 1 in a wild background (T1/W). D. Transgene T1 in a wild × domesticated background (T1/D) vs. T1 in a wild background (T1/W). Respective correlation coefficients (r) for each comparison can be found in Table 2.

Correlated effects on mRNA levels between domesticated and GH transgenic strains have also been observed in domesticated and GH transgenic coho salmon strains relative to wild-type (Devlin et al., 2009), suggesting this regulatory concordance may be more than a species-specific response. That study, however, did not examine the interaction of domesticated and transgenic genotypes whereas the present work has assessed multiple transgenic strains and hybrids between the transgenic and domesticated strains. Overall, influences on mRNA (in terms of number of genes affected and average change in mRNA levels) in the present study were found to vary in parallel with strain growth rate among the domesticated and transgenic genotypes. The effects of genetic background, however, were relatively small compared to the effect of either domestication or genetic modification alone (compared to wild-type). These data indicate that genetic background can act in concert with GH transgenesis but that the major influences on mRNA levels can arise from either type of genetic change (domestication or GH transgenesis) acting in isolation. That the observed changes are closely associated with growth

among strains is consistent with the affected genes being either causal of growth effects or are responding secondarily to the strong physiological changes occurring in the growth-stimulated strains. Indeed, examination of specific mRNA in GH transgenic coho salmon growing at their full rate or held to a wild growth rate by ration restriction found that many effects in transgenic fish are manifested only on receiving elevated food intake, which then allows for the increased growth in this genetic background (Overturf et al., 2010). Some GH transgenic strains in coho salmon appear to possess near maximal growth stimulation of the GH pathway because treatment with additional GH does not stimulate further growth (Raven et al., 2012) whereas other strains produce much lower levels of growth stimulation (Devlin et al., 2004; Leggatt et al., 2012). Domestication and genetic selection also can produce a range of growth stimulation effects, depending on the number of generations the strain has been under selection (Hershberger et al., 1990; Gjedrem et al., 2012). For strains that have been extensively selected for growth, it may be that further stimulation is more difficult to achieve without inducing

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5254

Devlin et al.

pathological effects. When a GH transgene was inserted into a very fast-growing domesticated strain of trout, little additional growth was observed (Devlin et al., 2001b), yet abnormalities analogous to acromegaly became apparent, consistent with GH/IGF-1/T3 metabolism pathways being overstimulated (see below). Similarly, treatment of Atlantic salmon with GH protein has a more pronounced effect in slow-growing wild than fast-growing domesticated strains (Neregard et al., 2008). In the present study, 1 transgene (T2) in a wild background was able to dramatically increase growth beyond that seen in pure domesticated or domesticated × wild hybrid nontransgenic genotypes. The other transgene (T1) in a wild genetic background was found to elevate growth rate to a similar extent as the pure domesticated strain. However, growth of T1 in a domesticated × wild hybrid background did not differ from T1 in a pure wild background whereas T2 in a domesticated × wild hybrid background did elevate growth rate further. Although not directly comparable, that T2 was able to increase growth rate beyond the level seen for domestication in the current study indicates the situation is more complicated than previously thought (Devlin et al., 2001a). These differences could be due to several factors. First, the domesticated strains used in the studies were different, with the present work being conducted with the Campbell Lake domesticated trout strain, which is significantly slower growing than the Spring Valley strain used previously (although both strains grow much faster than wild-type). In no case were abnormalities observed in the present study, suggesting the fish were not being growth stimulated to a pathological degree. Second, the genetic background in the present experiments was only 50% domesticated (i.e., F1 wild × domesticated trout hybrid) whereas in the previous study the background genotype was that of a pure domesticated strain. Therefore, the weaker growth phenotype of the domesticated strain and the wild × domesticated hybrid nature of the genetic background may have allowed strong GH transgenes to stimulate further growth. This is supported by the additive effects of the mRNA level analysis between the transgenic strains in the present study. It is also possible that the strong effect is specific to the T2 transgenic strain (e.g., due to chromosomal position, copy number at the locus, etc.) being able to add to the growth rate seen in a wide range of genetic backgrounds. This has not yet been tested and will require introduction of the T2 transgene into a fast-growing domesticated strain via repeated backcrossing and determination of the structural bases for the differences between strain T1 and T2, which are not yet known. In any case, the present data have confirmed that the growth effects and molecular influence (mRNA levels) of different transgenes can respond distinctly to genetic background. Background genetic influences on phenotypes in GH transgenic mice have also been observed (Eisen et al., 1993; Siewerdt et al., 1997, 1998, 2000).

Figure 5. Number of genes (n = 90) with assigned function affected among different cellular and organismal functions showing a greater than 2-fold difference in mRNA level in domesticated or transgenic genotypes relative to wild-type.

It is perhaps not unexpected that fast-growing animals generated by different genetic approaches would display similar changes in mRNA levels relative to wildtype. Growth stimulation has been found to influence the same pathways in similar ways (Devlin et al., 2009; Overturf et al., 2010; this study), but, as mentioned above, such responses may be either causal of growth effects or may arise as a consequence of those physiological changes. Studies examining causal differences between domesticated and wild salmonid strains using quantitative genetic approaches have found multiple loci playing a role, largely acting via additive genetic mechanisms (McClelland et al., 2005; Tymchuk and Devlin, 2005; Tymchuk et al., 2006; Fraser et al., 2010). Similarly, mapping studies examining F2 backcross progeny from domesticated × wild hybrids have found for coho salmon (McClelland and Naish, 2010) and rainbow trout (Wringe et al., 2010) that multiple QTL are responsible for controlling growth rate differences between domesticated and wild strains, consistent with a polygenic process involved during selection and domestication. Interestingly, genetic changes associated with domestication have also been found to occur very rapidly (Hershberger et al., 1990; Bidau, 2009; Gjedrem et al., 2012; Sauvage et al., 2010), in as little as a single generation (Christie et al., 2011). Notwithstanding the general similarities in mRNA patterns affected by domestication and GH transgenesis, it is not actually known which specific genetic loci are involved in altering phenotypes during animal domestication. In contrast, GH transgenesis arises from very specific engineering of a defined genetic change acting on a known physiological process. For transgenesis, direct effects arise from GH overexpression alone, causing a cascade of mRNA level and other downstream influences, whereas for domesticated animals, changes in mRNA levels may arise through accumulation of growth-promoting alleles at many loci, thus modifying multiple pathways

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5255

Domestication vs. transgenic effects on mRNA

Table 3. Levels of mRNA, relative to wild type, for genes displaying a greater than 2-fold reduction (bold) or elevation (italic) in mRNA in domesticated and at least 1 transgenic genotype Gene product (gene name)

Genbank accession number

D/D 0.47

T1/W 0.22

Genotype1 T1/D T2/W 0.16 0.31

Gene function T2/D 0.38 18S rRNA maturation, and 40S ribosome biogenesis.

RNA 3′-terminal phosphate cyclaselike protein (rcl1)

CA037656

Extracellular matrix protein 1 (ecm1) Glutathione S-transferase P (gst)

CA038043 CA050452

0.49

0.66 1.88

0.58

0.49

2.55

2.40

1.50

C-type lectin domain family 4 member E (clc4e)

CB511048

2.66

1.78

2.18

1.40

Transaldolase (taldo)

CA042536

2.16

2.77

2.61

2.02

Elongation of very long chain fatty acids protein 2 (elovl) Leukocyte cell-derived chemotaxin 2 precursor (lect2)

CA044333

2.03

2.49

3.04

3.31

2.34

CA037891

2.69

3.73

4.68

2.79

2.68

Lysozyme C II precursor (lyz2) Salmo salar insulin-like growth factor 2 (igf2)

CA054167 CA038357

5.49 2.30

1.96 0.51

3.51 1.32

2.33 0.86

2.98 3.02

Metallothionein A (mta)

CB492197

5.84

2.40

6.57

1.65

3.07

Pterin-4-alpha-carbinolamine dehydratase (phs) TSC22 domain family protein 4 (tsc22) Gastrulation-specific protein G12 (mid1)

CB497855

2.34

2.81

3.07

2.78

3.22

CB509522

2.78

5.09

4.50

5.61

5.87

CA054990

6.37

9.54

10.32

5.94

7.33

CA038900

7.90

15.12

19.02

18.41

18.99

Acyl-CoA desaturase (acod)

0.42

Bone and connective tissue structure Detoxification of hydrophobic and electrophilic compounds with glutathione. Xenobiotic metabolism. 1.42 Cell-surface receptor for damaged cells, fungi, and mycobacteria. 1.91 Pentose phosphate pathway for generation of NADPH2 and ribose for formation of ATP, DNA, and RNA. 1.36

Condensing enzyme that catalyzes the synthesis of polyunsaturated very long chain fatty acids. Has a neutrophil chemotactic activity. Also a positive regulator of chondrocyte proliferation. Antibacterial activity. Growth regulating, insulin-like, and mitogenic activities Metal binding for metabolism and xenobiotic excretion Phenylalanine hydroxylation. Regulates transcription factor hepatocyte nuclear factor 1 alpha. Transcription repressor, enhancer of cell proliferation, regulation of apoptosis Upregulates acetyl-CoA carboxylase enzyme activity for lipogenesis in liver. Microtubule stabilization. Desaturation of fatty acids

1W/W+1 = wild type trout 1 yr older (total 556 d) than all other groups (size matched at 191 d of age); D/D = pure domesticated strain; T1/W = T1 transgene in a pure wild genetic background; T1/D = T1 transgene in a wild × domesticated hybrid genetic background; T2/W = T2 transgene in a pure wild genetic background; T2/D, = T2 transgene in a wild × domesticated hybrid genetic background. 2NADPH = Nicotinamide Adenine Dinucleotide Phosphate, reduced form.

separately (albeit coordinated by the selection process). Alternatively, there could be a convergence of regulatory influences between domestication and GH transgenesis: domestication could modify higher-level regulators (such as GH), which change physiological processes in a similar fashion as seen for GH transgenesis. Indeed, endocrine and genetic studies in fish, chickens, and mammals have indicated that elevated levels of GH and/or IGF-1 or IGF2 can be associated with rapid growth in domesticated strains (i.e., large vs. small dogs, and wild vs. domesticated pigs), consistent with this axis having an important role (Eigenmann et al., 1984; Porter, 1998; Weiler et al., 1998; Favier et al., 2001; Fleming et al., 2002; Van Laere et al., 2003; Giachetto et al., 2004; Bunter et al., 2005; Decuypere, 2005; Tymchuk et al., 2009b). Furthermore, in mammals, strongly stimulating growth by GH transgenesis in highly domesticated strains has been problematic and has been associated with induction of abnormalities (analogous to acromegaly; Hammer et al., 1985; Pursel et al., 1989; Rexroad et al., 1989; Pinkert and Murray, 1999; Adams et al., 2002; Adams and Briegel, 2005), suggesting GH pathway signaling is already at a high level. There-

fore, for organisms that have a long history of domestication, such as terrestrial agricultural vertebrate species, stimulating growth beyond their base level by GH overexpression may be difficult. Overall, these data indicate an important role for the GH/IGF axis in domestication; however, the number of loci involved in such regulation is not known. Furthermore, for both GH and IGF-1, environmental conditions (e.g., ration level) can markedly influence their quantities (Duan, 1998; Beckman, 2011), and therefore, separating causal from consequential influences of these hormones regarding growth can be complex. Previous enzyme and mRNA (microarray) surveys have noted changes in a large number of genes affecting physiology and metabolism in domesticated and GH strains, relative to wild-type (Rise et al., 2006; Devlin et al., 2009; Leggatt et al., 2009; Normandeau et al., 2009; Tymchuk et al., 2009a; Bougas et al., 2010; Overturf et al., 2010; Debes et al., 2012; Drew et al., 2012; Sauvage et al., 2010). Major pathways affected include response to stimulus, generation of precursor metabolites and energy, cell and/or tissue structure and development, and protein

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5256

Devlin et al.

synthesis, metabolic, cell growth, immune function, and stress functions. In the present study, genes involved in lipid metabolism had mRNAs very strongly elevated both in domesticated and GH transgenic strains. Of note was an increase in Pterin-4-α-carbinolamine dehydratase mRNA, a dimerization cofactor that regulates liver transcription factor hepatocyte nuclear factor-1 α (HNF-1α), which itself possesses multiple functions including lipid metabolism (Rufibach et al., 2006). Gastrulation-specific protein G12 (involved in regulation of acetyl-CoA carboxylase) mRNA and acetyl-CoA desaturase mRNA were also both very strongly elevated in both domesticated and GH transgenic genotypes, consistent with the known lipid metabolism actions of GH (Harvey et al., 1995) and hence implicating similar effects in the domesticated strains analyzed here. TSC22 domain family protein-4, a transcription repressor involved in apoptosis and Ras/Raf signaling and cell growth (Nakamura et al., 2012), was also strongly enhanced by both domestication and GH transgenesis. In other vertebrates, QTL associated with specific genes have been found associated with domestication. For example, IGF-1 has been linked to body size among breeds of dogs (Sutter et al., 2007) consistent with a causal role for this locus. Multiple loci have now been clearly associated with domesticated vs. wild breeds of chickens, for example the TSHR gene influencing metabolism and reproduction and the PMEL17 locus affecting exploratory behavior (Rubin et al., 2010; Karlsson et al., 2010). Interestingly, exploratory and feeding behavior effects can also be affected by domestication and GH in fish (Johnsson and Björnsson, 1994; Devlin et al., 1999; Bessey et al., 2004; Sundström et al., 2007). It will be of interest to assess whether these alterations arise by common or distinct mechanisms among families of vertebrates. Assessing the interaction between transgenes and genetic background also has importance for risk assessments of transgenic organisms should they be introduced into nature. Regulatory assessments require understanding of a transgenic organism’s phenotype (e.g., competitive feeding ability) to determine whether those characteristics could cause harm to ecosystem components (e.g., other species). Understanding the stability (durability) of such traits is important to provide a robust assessment and to minimize uncertainty (Devlin et al., 2006; Kapuscinski et al., 2007). If a transgenic organism’s phenotype can shift, different magnitudes of transgene persistence and harms may ensue from those measured in a baseline strain under specific experimental assessment conditions. Indirect effects on nontransgenic genotypes in populations may also be anticipated in some cases if, for example, slowgrowth alleles are selected in nature in the presence of a growth-promoting transgene (i.e., to reduce transgenic animal phenotype back towards the naturally selected, and presumably optimal, growth rate found for wild-type

animals). In such a scenario, there is the potential to shift the type and distribution of natural variation in wild populations (Ahrens and Devlin, 2010). The present study has extended previous observations on the effects of genetic changes arising from domestication and from GH transgenesis, using salmonids as a model system. Although the action and interaction of these forms of genetic variation at the phenotypic and molecular levels is complex, varying with transgene strength and domesticated strain used, their common effects on many gene product levels suggests they have convergent influences on regulatory processes. Although the precise mechanisms by which domestication influences phenotype from wild-type are not yet understood, it is known that at least 15 major loci are involved in controlling growth rate differences between domesticated and wild rainbow trout (Wringe et al., 2010). The present data are consistent with the hypothesis that upregulation of the GH/IGF axis and/or its downstream effects plays a significant role in growth modification in domesticated strains. literature cited Adams, N. R., and J. R. Briegel. 2005. Multiple effects of an additional growth hormone gene in adult sheep. J. Anim. Sci. 83:1868–1874. Adams, N. R., J. R. Briegel, and K. A. Ward. 2002. The impact of a transgene for ovine growth hormone on the performance of two breeds of sheep. J. Anim. Sci. 80:2325–2333. Ahrens, R. N. M., and R. H. Devlin. 2010. Standing genetic variation and compensatory evolution in transgenic organisms: A growthenhanced salmon simulation. Transgenic Res. 20:583–597. Amaral, A. J., L. Ferretti, H. J. Megens, R. Crooijmans, H. S. Nie, S. E. Ramos-Onsins, M. Perez-Enciso, L. B. Schook, and M. A. M. Groenen. 2011. Genome-wide footprints of pig domestication and selection revealed through massive parallel sequencing of pooled DNA. PLoS ONE doi:10.1371/journal.pone.0014782 Beckman, B. 2011. Perspectives on concordant and discordant relations between insulin-like growth factor 1 (IGF1) and growth in fishes. Gen. Comp. Endocrinol. 170:233–252. Bessey, C., R. H. Devlin, N. R. Liley, and C. A. Biagi. 2004. Reproductive performance of growth-enhanced transgenic coho salmon (Oncorhynchus kisutch). Trans. Am. Fish. Soc. 133:1205–1220. Bidau, C. J. 2009. Domestication through the centuries: Darwin’s ideas and Dmitry Belyaev’s long-term experiment in silver foxes. Gayana (Zool.) 73:55–72. Bougas, B., S. Granier, C. Audet, and L. Bernatchez. 2010. The transcriptional landscape of cross-specific hybrids and its possible link with growth in brook charr (Salvelinus fontinalis Mitchill). Genetics 186:97–107. Bunter, K. L., S. Hermesch, B. G. Luxford, H.-U. Graser, and R. E. Crump. 2005. Insulin-like growth factor-I measured in juvenile pigs is genetically correlated with commercially important performance traits. Aust. J. Exp. Agric. 45:783–792. Christie, M. R., M. L. Marinea, R. A. French, and M. S. Blouin. 2011. Genetic adaptation to captivity can occur in a single generation. Proc. Natl. Acad. Sci. USA 109:238–242.

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

Domestication vs. transgenic effects on mRNA Debes, P. V., E. Normandeau, D. J. Fraser, L. Bernatchez, and J. A. Hutchings. 2012. Differences in transcription levels among wild, domesticated, and hybrid Atlantic salmon (Salmo salar) from two environments. Mol. Ecol. 21:2574–2587. Decuypere, E. 2005. Endocrine control of postnatal growth in poultry. Jpn. Poult. Sci. 42:1–13. Devlin, R. H., C. A. Biagi, and D. E. Smailus. 2001a. Genetic mapping of Y-chromosomal DNA markers in Pacific salmon. Genetica (The Hague) 111:43–58. Devlin, R. H., C. A. Biagi, and T. Y. Yesaki. 2004. Growth, viability and genetic characteristics of GH transgenic coho salmon strains. Aquaculture 236:607–632. Devlin, R. H., C. A. Biagi, T. Y. Yesaki, D. E. Smailus, and J. C. Byatt. 2001b. Growth of domesticated transgenic fish. Nature 409:781–782. Devlin, R. H., J. I. Johnsson, D. E. Smailus, C. A. Biagi, E. Jonsson, and B. T. Bjornsson. 1999. Increased ability to compete for food by growth hormone-transgenic coho salmon, Oncorhynchus kisutch (Walbaum). Aquacult. Res. 30:479–482. Devlin, R. H., D. Sakhrani, W. E. Tymchuk, M. L. Rise, and B. Goh. 2009. Domestication and growth hormone transgenesis cause similar changes in gene expression in coho salmon (Oncorhynchus kisutch). Proc. Natl. Acad. Sci. USA 106:3047–3052. Devlin, R. H., L. F. Sundstrom, and W. M. Muir. 2006. Interface of biotechnology and ecology for environmental risk assessments of transgenic fish. Trends Biotechnol. 24:89–97. Drew, R. E., M. L. Settles, E. J. Churchill, S. M. Williams, S. Balli, and B. D. Robison. 2012. Brain transcriptome variation among behaviorally distinct strains of zebrafish (Danio rerio). BMC Genomics 13:323. Duan, C. 1998. Nutritional and developmental regulation of insulinlike growth factors in fish. J. Nutr. 128:306S–314S. Eigenmann, J. E., D. F. Patterson, J. Zapf, and E. R. Froesch. 1984. Insulin-like growth factor-i in the dog a study in different dog breeds and in dogs with growth hormone elevation. Acta Endocrinol. (Copenh.) 105:294–301. Eisen, E. J., M. Fortman, W. Y. Chen, and J. J. Kopchick. 1993. Effect of genetic background on growth of mice hemizygous for wild-type or dwarf mutated bovine growth hormone transgenes. Theor. Appl. Genet. 87:161–169. Favier, R. P., J. A. Mol, H. S. Kooistra, and A. Rijnberk. 2001. Large body size in the dog is associated with transient GH excess at a young age. J. Endocrinol. 170:479–484. Fleming, I., T. Agustesson, B. Finstad, J. Johnsson, and B. Bjornsson. 2002. Effects of domestication on growth physiology and endocrinology of Atlantic salmon (Salmo salar). Can. J. Fish. Aquat. Sci. 59:1323–1330. Fraser, D. J., A. L. S. Houde, P. V. Debes, P. O’Reilly, J. D. Eddington, and J. A. Hutchings. 2010. Consequences of farmed-wild hybridization across divergent wild populations and multiple traits in salmon. Ecol. Appl. 20:935–953. Giachetto, P., E. Riedel, J. Gabriel, M. Ferro, S. Di Mauro, M. Macari, and J. Ferro. 2004. Hepatic mRNA expression and plasma levels of insulin-like growth factor-I (IGF-I) in broiler chickens selected for different growth rates. Genet. Mol. Biol. 27:39–44. Gjedrem, T., N. Robinson, and M. Rye. 2012. The importance of selective breeding in aquaculture to meet future demands for animal protein: A review. Aquaculture 350–353:117–129. Hammer, R. E., R. L. Brinster, and R. D. Palmiter. 1985. Genetically engineered farm animals come closer to reality. Genet. Technol. News 5:5. Harvey, S., C. G. Sacnes, and W. H. Daughaday. 1995. Growth hormone. CRC Press, Boca Raton, FL.

5257

Hershberger, W. K., J. M. Myers, R. N. Iwamoto, W. C. Macauley, and A. M. Saxton. 1990. Genetic changes in the growth of coho salmon (Oncorhynchus kisutch) in marine net-pens, produced by ten years of selection. Aquaculture 85:187–197. Johnsson, J. I., and B. T. Björnsson. 1994. Growth hormone increases growth rate, appetite and dominance in juvenile rainbow trout, Oncorhynchus mykiss. Anim. Behav. 48:177–186. Kapuscinski, A. R., K. R. Hayes, S. Li, and G. Dana. 2007. Environmental risk assessment of genetically modified organisms. Vol. 3. Methodologies for transgenic fish. CABI Int., Oxfordshire, UK. Karlsson, A. C., S. Kerje, L. Andersson, and P. Jensen. 2010. Genotype at the PMEL17 locus affects social and explorative behaviour in chickens. Br. Poult. Sci. 51:170–177. Koop, B. F., K. R. von Schalburg, J. Leong, N. Walker, R. Lieph, G. A. Cooper, A. Robb, M. Beetz-Sargent, R. A. Holt, R. Moore, S. Brahmbhatt, J. Rosner, C. E. Rexroad, C. R. McGowan, and W. S. Davidson. 2008. A salmonid EST genomic study: Genes, duplications, phylogeny and microarrays. BMC Genomics 9:545. Le Rouzic, A., J. M. Alvarez-Castro, and O. Carlborg. 2008. Dissection of the genetic architecture of body weight in chicken reveals the impact of epistasis on domestication traits. Genetics 179:1591–1599. Leggatt, R., C. Biagi, J. L. Smith, and R. H. Devlin. 2012. Growth of growth hormone transgenic coho salmon Oncorhynchus kisutch is influenced by construct promoter type and family line. Aquaculture 356–357:193–199. Leggatt, R. A., P. A. Raven, T. P. Mommsen, D. Sakhrani, D. Higgs, and R. H. Devlin. 2009. Growth hormone transgenesis influences carbohydrate, lipid and protein metabolism capacity for energy production in coho salmon (Oncorhynchus kisutch). Comp. Biochem. Physiol. B 154:121–133. Li, Q. H., N. Wang, Z. Du, X. X. Hu, L. Chen, J. Fei, Y. Y. Wang, and N. Li. 2012. Gastrocnemius transcriptome analysis reveals domestication induced gene expression changes between wild and domestic chickens. Genomics 100:314–319. McClelland, E. K., J. M. Myers, J. J. Hard, L. K. Park, and K. A. Naish. 2005. Two generations of outbreeding in coho salmon (Oncorhynchus kisutch): Effects on size and growth. Can. J. Fish. Aquat. Sci. 62:2538–2547. McClelland, E., and K. Naish. 2010. Quantitative trait locus analysis of hatch timing, weight, length and growth rate in coho salmon, Oncorhynchus kisutch. Heredity 105:562–573. Nakamura, M., J. Kitaura, Y. Enomoto, Y. Lu, K. Nishimura, M. Isobe, K. Ozaki, Y. Komeno, F. Nakahara, T. Oki, H. Kume, Y. Homma, and T. Kitamura. 2012. Transforming growth factor-β-stimulated clone-22 is a negative-feedback regulator of Ras/Raf signaling: Implications for tumorigenesis. Cancer Sci. 103:26–33. Neregard, L., L. Sundt-Hansen, K. Hindar, S. Einum, J. I. Johnsson, R. H. Devlin, I. A. Fleming, and B. T. Bjornsson. 2008. Wild Atlantic salmon Salmo salar L. strains have greater growth potential than a domesticated strain selected for fast growth. J. Fish Biol. 73:79–95. Normandeau, E., J. A. Hutchings, D. J. Fraser, and L. Bernatchez. 2009. Population-specific gene expression responses to hybridization between farm and wild Atlantic salmon. Evol. Appl. 2:489–503. Overturf, K., D. Sakhrani, and R. H. Devlin. 2010. Expression profile for metabolic and growth-related genes in domesticated and transgenic coho salmon (Oncorhynchus kisutch) modified for increased growth hormone production. Aquaculture 307:111–122. Pinkert, C. A., and J. D. Murray. 1999. Transgenic farm animals. In: J. D. Murray, G. B. Anderson, A. M. Oberbauber, and M. M. McGloughlin, editors, Transgenic animals in agriculture. p. 1–18. Porter, T. E. 1998. Differences in embryonic growth hormone secretion between slow and fast growing chicken strains. Growth Horm. IGF Res. 8:133–139.

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

5258

Devlin et al.

Pursel, V. G., C. A. Pinkert, K. F. Miller, D. J. Bolt, R. G. Campbell, R. D. Palmiter, R. L. Brinster, and R. E. Hammer. 1989. Genetic engineering of livestock. Science 244:1281–1288. Pursel, V. G., R. J. Wall, M. B. Solomon, D. J. Bolt, J. D. Murray, and K. A. Ward. 1997. Transfer of an ovine metallothionein-ovine growth hormone fusion gene into swine. J. Anim. Sci. 75:2208–2214. Raven, P. A., D. Sakhrani, B. Beckman, L. Neregard, L. F. Sundstrom, B. T. Bjornsson, and R. H. Devlin. 2012. Growth and endocrine effects of recombinant bovine growth hormone treatment in non-transgenic and growth hormone transgenic coho salmon. Gen. Comp. Endocrinol. 177:143–152. Rexroad, C. E. J., R. E. Hammer, D. J. Bolt, K. E. Mayo, L. A. Frohman, R. D. Palmiter, and R. L. Brinster. 1989. Production of transgenic sheep with growth-regulating genes. Mol. Reprod. Dev. 1:164–169. Rexroad, C. E. J., K. Mayo, D. J. Bolt, T. H. Elsasser, K. F. Miller, R. R. Behringer, R. D. Palmiter, and R. L. Brinster. 1991. Transferrin-directed and albumin-directed expression of growth-related peptides in transgenic sheep. J. Anim. Sci. 69:2995–3004. Rise, M. L., S. E. Douglas, D. Sakhrani, J. Williams, K. V. Ewart, M. Rise, W. Davidson, B. Koop, and R. H. Devlin. 2006. Multiple microarray platforms utilized for hepatic gene expression profiling of GH transgenic coho salmon with and without ration restriction. J. Mol. Endocrinol. 37:259–282. Rozycki, M., Z. Smorag, J. J. Kopchick, W. Y. Chen, J. Jura, J. Pasieka, B. Orzechowska, B. Gajda, and M. Skrzyszowska. 1999. Performance of transgenic pigs produced with the use of two different growth hormone gene constructs. J. Appl. Genet. 40:29–37. Rubin, C.-J., M. Zody, J. Eriksson, J. Meadows, E. Sherwood, M. Webster, L. Jiang, M. Ingman, T. Sharpe, S. Ka, F. Hallbook, F. Besnier, O. Carlborg, B. Bed’hom, M. Tixier-Boichard, P. Jensen, P. Siegel, K. Lindblad-Toh, and L. Andersson. 2010. Whole-genome resequencing reveals loci under selection during chicken domestication. Nature 464:587–593. Rufibach, L., S. Duncan, M. Battle, and S. Deeb. 2006. Transcriptional regulation of the human hepatic lipase (LIPC) gene promoter. J. Lipid Res. 47:1463–1477. Sauvage, C., N. Derome, E. Normandeau, J. St-Cyr, C. Audet, and L. Bernatchez. 2010. Fast transcriptional responses to domestication in the Brook Charr, Salvelinus fontinalis. Genetics 185:105–112. Siewerdt, F., E. J. Eisen, J. S. Conrad-Brink, and J. D. Murray. 1998. Gene action of the oMt1a-oGH transgene in two lines of mice with distinct selection backgrounds. J. Anim. Breed. Genet. 115:211–226.

Siewerdt, F., E. J. Eisen, J. D. Murray, and J. S. Conrad-Brink. 1997. Gene action of the oMt1a-oGH transgene in two lines of mice with distinct selection backgrounds. In: 89th Annual Meeting of the American Society of Animal Science, Nashville, TN. July 29-August 1, 1997. Siewerdt, F., E. J. Eisen, J. D. Murray, and I. J. Parker. 2000. Response to 13 generations of selection for increased 8-week body weight in lines of mice carrying a sheep growth hormone-based transgene. J. Anim. Sci. 78:832–845. Sundström, L. F., M. Lohmus, J. I. Johnsson, and R. H. Devlin. 2007. Dispersal potential is affected by growth-hormone transgenesis in coho salmon (Oncorhynchus kisutch). Ethology 113:403–410. Sutter, N. B., C. D. Bustamante, K. Chase, M. M. Gray, K. Zhao, L. Zhu, B. Padhukasahasram, E. Karlins, S. Davis, P. G. Jones, P. Quignon, G. S. Johnson, H. G. Parker, N. Fretwell, D. S. Mosher, D. F. Lawler, E. Satyaraj, M. Nordborg, K. G. Lark, R. K. Wayne, and E. A. Ostrander. 2007. A single IGF1 allele is a major determinant of small size in dogs. Science 316:112–115. Tymchuk, W., D. Sakhrani, and R. Devlin. 2009a. Domestication causes large-scale effects on gene expression in rainbow trout: Analysis of muscle, liver and brain transcriptomes. Gen. Comp. Endocrinol. 164:175–183. Tymchuk, W. E., B. Beckman, and R. H. Devlin. 2009b. Altered expression of growth hormone/insulin-like growth factor I axis hormones in domesticated fish. Endocrinology 150:1809–1816. Tymchuk, W. E., C. Biagi, R. Withler, and R. H. Devlin. 2006. Growth and behavioral consequences of introgression of a domesticated aquaculture genotype into a native strain of Coho salmon. Trans. Am. Fish. Soc. 135:442–455. Tymchuk, W. E., and R. H. Devlin. 2005. Growth differences among first and second generation hybrids of domesticated and wild rainbow trout (Oncorhynchus mykiss). Aquaculture 245:295–300. Van Laere, A. S., M. Nguyen, M. Braunschweig, C. Nezer, C. Collette, L. Moreau, A. L. Archibald, C. S. Haley, N. Buys, M. Tally, G. Andersson, M. Georges, and L. Andersson. 2003. A regulatory mutation in IGF2 causes a major QTL effect on muscle growth in the pig. Nature 425:832–836. Weiler, U., R. Claus, S. Schnoebelen-Combes, and I. Louveau. 1998. Influence of age and genotype on endocrine parameters and growth performance: A comparative study in Wild boars, Meishan and Large White boars. Livest. Prod. Sci. 54:21–31. Wringe, B., R. Devlin, M. Ferguson, H. Moghadam, D. Sakhrani, and R. Danzmann. 2010. Growth-related quantitative trait loci in domestic and wild rainbow trout (Oncorhynchus mykiss). BMC Genet. 11:63–77.

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

References

This article cites 63 articles, 16 of which you can access for free at: http://www.journalofanimalscience.org/content/91/11/5247#BIBL

Downloaded from www.journalofanimalscience.org at ProQuest on November 11, 2013

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.