Project website : http://www.ualg.pt/ccmar/fishcal
Partners of the project :
Links to the .ppt from Faro meeting:
Project summary :
Despite improved methodologies for farming of marine fish species, the viability of egg and larvae is still, in most cases, no more than 20-30%. This is as a consequence of high mortalities and/or a high incidence of larvae with skeletal deformities (dystrophies). Often dystrophies are not immediately apparent leading to a wasteful use of food, energy, space and human resources until dystrophic fish are graded and removed. Skeletal deformities arise as a consequence of abnormal calcification of cartilaginous tissue and there is evidence that hypercalcaemic factors may be involved. Therefore, the elucidation of the processes controlling ossification in fish larvae is of extreme importance in order to devise culture methodologies that minimise abnormal development. Calcium is also important in a range of other physiological processes of practical importance to aquaculture, such as during reproduction when high concentrations of calcium need to be available for vitellogenesis and for growth, which requires both bone remodelling and ossification. Surprisingly there is relatively little information available about how calcium requirements vary in teleost fish during their life cycle or the physiological mechanisms employed to raise plasma calcium levels. The aim of this project is to determine how calcium homeostasis and availability is maintained during critical stages of the life cycle of the teleost fish Sparus aurata, an important marine aquaculture species in Southern European countries. Whilst hypocalcaemic factors, such as stanniocalcin and calcitonin, have been identified and characterised in fish, until now there has been no recognised hypercalcaemic factor. However, the project partners have cloned and identified a gene in sea bream for a potential hypercalcaemic factor, parathyroid hormone-related protein (PTHrP) and shown that teleost PTHrP does elevate internal calcium. This discovery indicates that raising circulating calcium levels is an important physiological function but the mechanisms by which this is achieved are currently unknown. The Fishcal project will start by generating new, specific tools based on the genomic information available, which will be used as reagents and assay methods in the experiments to be carried out. Then a series of studies will follow to evaluate calcium requirements and the source of calcium in rapidly growing fish and in larvae undergoing skeletal development. The way in which calcium homeostasis is maintained in changing conditions of calcium availability, and the role of PTHrP, its receptor and of the calcium sensing receptor in this process will be elucidated. A similar approach will be taken to study calcium homeostasis during vitellogenesis when high loads of calcium are required for gamete development and maturation. In a third phase the molecular mechanisms, which underpin bone formation in fish, will be studied. This will involve the identification of genes activated during initiation of endochondral bone formation and characterisation of their response to the presence of PTHrP. Factors which regulate the PTHrP gene expression, and thus ossification, will be identified by studying the promoter region of the PTHrP gene. The overall achievement of the project will be to provide new information about calcium physiology in sea bream hitherto unavailable. This will allow the identification of causal factors in abnormal bone development in larvae, the mechanism by which calcium is incorporated into vitellogenin, the general requirements of calcium for normally growing fish and the function of PTHrP in these processes.
List of genomic tools generated in the project :
Publications generated in the project :