Proteomic comparison of selective breeding and growth hormone transgenesis in fish: Unique pathways to enhanced growth

In fish used for food production and scientific research, fast growth can be achieved via selective breeding or induced instantaneously via growth hormone (GH) transgenesis (GHT). The proteomic basis for these distinct routes towards a similar higher phenotype remains uncharacterized, as are associated implications for health parameters. We addressed this knowledge gap using skeletal muscle proteomics in coho salmon (Oncorhynchus kisutch), hypothesising that i) selective breeding and GHT are underpinned by both parallel and unique changes in growth systems, and ii) rapidly-growing fish strains have lowered scope to allocate resources towards immune function. Quantitative profiling of GHT and growth-selected strains was done in comparison to wild-type after injection with PBS (control) or Poly I:C (to mimic infection). We identified remodelling of the muscle proteome in each growth-enhanced strain that was strikingly non-overlapping. GHT was characterized by focal upregulation of systems driving protein synthesis, while the growth-selected fish presented a larger and more diverse set of changes, consistent with complex alterations to many metabolic and cellular pathways. Poly I:C had little detectable effect on the muscle proteome. This study demonstrates that distinct proteome profiles can explain outwardly similar enhanced growth phenotypes, improving our understanding of growth mechanisms in anthropogenic animal strains.

Significance
This work provides the first proteomic insights into mechanisms underpinning different anthropogenic routes to rapid growth in salmon. High-throughput proteomic profiling was used to reveal changes supporting enhanced growth, comparing skeletal muscle of growth hormone transgenic (GHT) and selectively-bred salmon strains with their wild-type counterparts. Contrasting past mRNA-level comparisons of the same fish strains, our data reveals a surprisingly substantial proteomic divergence between the GHT and selectively bred strains. The findings demonstrate that many unique molecular mechanisms underlie growth-enhanced phenotypes in different types of fish strain used for food production and scientific research.