Eating behaviour regulation in Zebrafish (Danio rerio): a comparative analysis

The structure, function, and tissue specific expression profiles of neuropeptides involved in regulating eating behaviour are well researched in mammals, the corresponding literature on fish homologs however is scarce. The work presented here endeavoured to characterise the full coding sequences of peptide homologs in zebrafish as well as the expression profiles of said peptides under different energy states to elucidate their function in fish. Zebrafish were chosen as a model to represent fish species as they are amenable to molecular study. Conducting a literature and TBLASTn search, genes were identified in zebrafish that are known to be involved in affecting appetite and satiety in other vertebrates. Comparison of the translated sequences of these genes against fish and other vertebrates provided confidence in the identity of AGRP, GHRL, POMCb, CART1, CART3, and CART4 and all genes showed homology against mammalian transcripts through structural and syntenic comparison. RACE synthesis of the full coding sequence of these genes was attempted from isolated brain mRNA but only resulted in the production of a partial 3’ sequence for CART1 and CART4 which showed high identity against the predicted nucleotide but not the translated sequence. To observe the functional properties of a suite of genes, a qPCR analysis of the expression profiles of AGRP, GHRL, POMCa, POMCb, CART1, CART2, CART3, CART4, OXT, NPY, and AVPwas undertaken in 24 hour fasted zebrafish. The results were comparable to both other fish and mammals as AGRP was orexigenically upregulated in fasted zebrafish, while POMCb and OXT were anorexigenically downregulated. This is the first time that an expression study has been conducted across all of these genes together in a single species and, while the results are preliminary, they outline that the simultaneous analysis of the many genes thought to be involved in eating behaviour is a viable approach to discovering the functional roles of the range of genes, their interaction with each other, and how that relates to eating behaviour and provides some confidence in use of zebrafish as a model to highlight this