title: Growth and endocrine effect of growth hormone transgene dosage in diploid and triploid coho salmon.
abstract: Growth-hormone transgene dosage, polyploidy, and parental effects on growth and endocrine responses have been assessed in coho salmon. Diploid fry with one or two transgene doses grew equally, whereas later-stage juvenile homozygotes grew faster than hemizygotes. In contrast, homozygotes and hemizygotes grew equally after smoltification, both in sea water and fresh water. Triploid transgenic salmon showed impaired growth which could not be fully overcome with additional transgene copies. Levels of muscle GH mRNA were elevated in two vs. one transgene dose diploids, but in triploids, a dosage effect was observed in muscle but not for animals carrying three transgene doses. IGF-I mRNA levels were elevated in transgenic vs. non-transgenic animals, but a dosage effect was not observed. Diploids and triploids with two transgenes had higher plasma GH levels than one-dose animals, but three-dose triploids showed no further elevation. Circulating IGF-I levels also showed a dosage effect in diploids, but not among any transgene doses in triploids. The present study reveals complex interactions among transgene dosage, maternal effects, developmental stage, and ploidy on growth and endocrine parameters in GH transgenic coho salmon. Specifically, GH transgenes do not always express nor have effects on growth that are directly correlated with the number of transgenes. Further, the reduced growth rate seen in triploid transgenic animals could not be fully overcome by increasing transgene dosage. The findings have relevance for understanding growth physiology, transgene function, and for environmental risk assessments that require understanding phenotypes of hemizygous vs. homozygous transgenic animals in populations.
authors: Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC V7K 1N6, Canada. Electronic address: robert.devlin@dfo-mpo.gc.ca.
authors: Robert H
authors: RH
authors: Devlin
authors: Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC V7K 1N6, Canada.
authors: Dionne
authors: D
authors: Sakhrani
authors: Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC V7K 1N6, Canada.
authors: Carlo A
authors: CA
authors: Biagi
authors: Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC V7K 1N6, Canada.
authors: Jack L
authors: JL
authors: Smith
authors: Faculty and Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
authors: Takafumi
authors: T
authors: Fujimoto
authors: Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA.
authors: Brian
authors: B
authors: Beckman
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics / Q000254:growth & development; D004171:Diploidy; D004703:Endocrine System / Q000187:drug effects / Q000502:physiology*; D013006:Growth Hormone / Q000235:genetics* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011863:Radioimmunoassay; D012474:Salmon / Q000235:genetics* / Q000254:growth & development*; D019076:Transgenes / Q000502:physiology*; D057885:Triploidy
chemical_list: D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone
keywords: Dosage; GH; Growth; Salmon; Transgenic; Triploid