title: Differential expression of the two GH genes during embryonic development of rainbow trout Oncorhynchus mykiss in relation with the IGFs system.
abstract: The Growth hormone (GH)/insulin-like growth factor (IGF) system promotes embryonic growth in higher vertebrates. Such a system exists in salmonids, but exhibits an additional level of complexity resulting from a recent whole genome tetraploidisation. Thus, two nonallelic GH genes are present in the trout genome. Although the two GH genes are similar, the possibility remains that the two genes have evolved separately, acquiring a distinct expression pattern. In this study, using whole mounted in situ hybridisation, we observed a one stage delay between the appearance of GH-2 (Stage 22) and GH-1 (Stage 23) soon after pituitary formation (Stage 21). In addition, by double in situ hybridisation, we clearly evidenced two types of somatotroph, one expressing only GH-2 and the other type both GH-1 and GH-2 at Stage 24. Consequently, at this stage more cells expressed GH-2 than GH-1 as confirmed by quantitative RT-PCR. However at hatching, as in adult, the difference between the expression of the two GH genes was no longer observed. In addition, our immunohistochemical studies did not show any delay between the expression of the mRNA and its translation as a protein at Stage 24. A comparison of the expression pattern of the IGF system components (IGF-1, IGF-2, and the receptor type I) determined by real time RT-PCR, have shown an IGF-1 mRNA increase concomitantly to the appearance of GH expression. On the whole, our results demonstrate a differential regulation of GH-1 and GH-2 genes in rainbow trout embryo. The relationship observed between the expression of different component of the GH/IGF system seems to indicate that this system could be functional early on during embryonic development.
authors.affiliation: Station Commune de Recherches en Ichtyophysiologie, Biodiversité et Environnement SCRIBE-INRA Campus, Beaulieu 35042, Rennes Cedex, France.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Gabillard
authors.forename: Hélène
authors.initials: H
authors.lastname: Duval
authors.forename: Chantal
authors.initials: C
authors.lastname: Cauty
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Rescan
authors.forename: Claudine
authors.initials: C
authors.lastname: Weil
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Le Bail
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000196:embryology* / Q000235:genetics; D012333:RNA, Messenger; D017451:Receptors, Somatomedin / Q000235:genetics; D016415:Sequence Alignment; D013002:Somatomedins / Q000235:genetics / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D017451:Receptors, Somatomedin; D013002:Somatomedins; D013006:Growth Hormone