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fPPARs
Cloning and functional analysis of fish peroxisome proliferator-activated receptors: The transcriptional control of lipid metabolism in farmed fish species

Among the major problems encountered in intensive fish aquaculture, the accumulation of fat in the tissues of farmed fish and the dependency of the aquaculture industry on fish oils for high-quality feeds are issues of exceptional economic interest. These problems can only be efficiently addressed by an increased understanding of the processes involved in lipid homeostasis in fish. The work proposed here will be accomplished through the cloning and functional analysis of fish peroxisome proliferator activated receptors (PPARs). PPARs are lipid-activable transcription factors that regulate both arms of lipid homeostasis in higher vertebrates. This study intends to provide the scientific background necessary for innovative solutions to the lipid metabolism-associated problems encountered in aquaculture and thus to contribute towards the sustainability of the industry.

Objectives
The specific objectives of this project are:
1) to clone and characterise the PPAR genes and cDNAs from four fish species of particular importance to the European aquaculture industry, i.e. sea bass (Dicentrarchus labrax), sea bream (Sparus aurata), Atlantic salmon (Salmo salar), and plaice (Pleuronectes platesa)
2) to study the functional properties of fish PPARs (fPPARs), i.e. their DNA and ligand binding properties, the PPAR-dependent transcriptional activation, and the expression pattern of PPARs in fish tissues; to establish species-specific and PPAR subtype-specific differences in the above described properties; to identify potent subtype-specific ligands for the fPPARs
3) to develop appropriate in vitro assays, i.e. cell and tissue culture systems, that will be used to establish clearly the role of PPARs in lipid metabolism in fish.
4) to examine in vivo the effect of induced PPAR expression and PPAR-dependent transcriptional activation on fat accumulation and lipid composition in fish tissues.

Progress to Date
The project is now in its third and final year, and has progressed according to schedule. New knowledge has been generated concerning the biology of PPARs in fish (the presence of different subtypes, expression profile, DNA and ligand binding properties) and tools have been developed for the study of these transcription factors, both in cellulo and in vivo.

Results
The new scientific data that have been produced in the frame of this project include:
1) the cloning and sequence analysis of three PPAR subtypes from sea bass, sea bream, Atlantic salmon, and plaice
2) the development of fish PPAR (fPPAR) subtype-specific antibodies, used in the study of the functional properties of the fPPARs
3) protocols have been established for the primary culture of hepatocytes, adipocytes, and enterocytes from the fish species studied. These primary cell culture systems will provide a valuable tool for the in cellulo study of the fPPAR properties.
The above results will allow the study of the properties of fPPARs both in vitro and in vivo. Concerning the functional properties of the fPPARs, i.e. transcription activation properties, tissue distribution, and DNA and ligand binding properties, preliminary results support the hypothesis that these receptors have functions similar to those of their mammalian homologues and are, therefore, key regulators of lipid homeostasis in fish.

Classified in FISHERIES AND AQUACULTURE, GENOMICS

Scientist responsible for the project

Dr GRIGORIOS KREY
Nea Peramos
64007 Kavala
Greece - GR

Phone: +30 25940 22691
Fax: +30 25940 22222
E-mail: krey@otenet.gr

References

Project ID QLRT-1999-30360
Organisation National Agricultural Research Foundation - Fisheries Research Institute
Area 5.1.2
Start date 01 December 2000
Duration (months) 36
Total cost 868 426 €
Total EC contribution   825 000 €
Status Completed

The partners

  • National Agricultural Research Foundation - Fisheries Research Institute, Greece - GR
    krey@otenet.gr
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