|Titre||An insulin-like system involved in the control of Pacific oyster Crassostrea gigas reproduction: hrIGF-1 effect on germinal cell proliferation and maturation associated with expression of an homologous insulin receptor-related receptor|
|Type de publication||Journal Article|
|Year of Publication||2006|
|Auteurs||Gricourt, L, Mathieu, M, Kellner-Cousin, K|
The putative involvement of insulin-like peptides in the control of the reproduction of the Pacific oyster Crassostrea gigas was investigated using different approaches. In conjunction with a monthly histological analysis of the oyster reproductive cycle, in vitro biological effects of the human recombinant IGF-1 (hrIGF-1) on dissociated germinal cells were mesured over 1 year using [3H]-thymidine and [14C]-amino acid mixture as tracers for DNA and protein synthesis. DNA synthesis was stimulated by hrIGF-1 in November (114 ± 11% for 10-7M), December (46 ± 6% for 10-7 M) and January, which was identified as the highest gonial mitosis period. A clear dose–effect was observed in January with a maximum activation of 68 ± 7% for 10-12 M. Germinal cell protein synthesis was also stimulated in March (20 ± 1% for 10-10 M), April (41 ± 5% for 10-13 M), May (25 ± 4% for 10-13 M), and by almost all of hrIGF-1 doses in June (21.5 ± 2% for 10-13 M) and July (34 ± 1% for 10-13 M). This suggests the involvement of insulin-like substances in gonadal tubule rebuilding (December), as well as in the development of germinal cells (March, April), and in the summer maturation of gametes (May, June, July). These insulin-like effects conform with the expression pattern of the recently identified C. gigas insulin receptor-related receptor (CIR): It appeared highly expressed in the gonadal area during gonial mitosis phase, but also in maturating oocytes, suggesting the involvement of an insulin-like system in gonial proliferation and maturation. Moreover, CIR showed differential expression during embryogenesis and larval developmental stages. The expression of maternal CIR during the embryonic and early larval development, followed by the increasing zygotic CIR expression from D larvae to 11-day-old veliger larvae, then a decrease until metamorphosis, also suggest that insulin-like peptide is involved in organogenesis.