Differential protein expression in relation to dietary amino acid composition: a proteomic approach towards understanding growth in fish

Growth is essentially protein deposition. Therefore, optimisation of growth depends on the understanding of amino acid (AA) metabolism. The complexity and possible interactions between the various metabolic processes and regulatory pathways are enormous. It is evident that growth in a living animal cannot be fully understood by studying one or a few factors at the time. This project aims at establishing proteomics as a tool towards getting a holistic understanding of the effects of dietary manipulation of AA on metabolism and growth in fish. The proteome is the composition of all proteins expressed by the genome of an organism. The central objective of this study is to screen the proteome of target organ systems (the digestive system including the liver, and muscle) for differentially expressed genes in fish fed diets with different nitrogen sources, amino acid profiles and degree of hydrolysis, in order to allow a better understanding of the dietary nitrogen digestion, absorption and the post absorptive metabolism including muscle growth and bone formation. We have selected Zebrafish as a model because of the advanced knowledge of its genome, a prerequisite for proteomic studies. The last year of the study will include a transfer of methods and start co mparative analysis of Atlantic cod. Amino acid sequence for specific proteins will primarily be identified by mass specific finger print analysis, but also N-terminal peptide sequencing. Comparative proteomics will allow identification of conserved protei n motifs. Based on an unbiased differential protein profile analysis we will identify protein clusters, characteristic of a certain proteomic phenotype and identify modulated proteins in the selected organs in response to the given dietary stimuli.