Implication des molécules du système insuline/IGF dans la croissance et la reproduction de l'huître creuse Crassostrea gigas : effets biologiques in vitro d'un ligand hétérologue (IGF-1 recombinant humain), caractérisation et expression d'un récepteur homologue de type insuline

Oyster rearing along the French Atlantic coastline relies upon a single species, the Pacific oyster Crassostrea gigas. ln this context, understanding of reproduction and growth processes would be useful to cope with the difficulties coming upon the profession - spawn obtention, swnmer mortalities, epizootie risks and growth problems. lnvolvement of some molecules belonging to insulinlIGF superfamily in regulation of growth and reproduction has been investigated in C. gigas.ln vitro biological effects ofhwnan recombinant IGF-1 (IGF-1 rh) on gonadic and mantle edge cells - which are target tissues to oyster reproduction, somatic growth and shell growth - have been followed up during an annual cycle: - IGF-1 rh stimulates cell prolitèration during germinal cells multiplication stage (68% at 10-12 M). It also activates genninal cells protein synthesis during gametes development and maturation (41% at 10-13 M). - IGF-1 rh stimulates mantle edge cells prote in synthesis during oyster soft tissues growth (57,5% at 10-11 M) and active shell growth (56% at 10-10 M). These results indicate that C. gigas reproduction and growth may be under partial control of some insulinlIGF-like molecules. Insulin/IGF-likes seasonal effect on those biological processes can be associated with differential expression oftheir specific receptors. ln C. gigas, the occurrence of such a receptor has been enlightened studying the shi ft of IGF-1 rh binding to its target tissues. Furthermore, a homologous insulin-like receptor has been characterised using a molecular biology approach. This receptor presents a relative conservation when compared to other members of the family. !ts expression is ubiquitous during adult stage even though expression level is tissue specific. The receptor also shows a differential pattern of expression during larval development.