Molecular cloning and characterization of gonadotropin subunits (GTHα, FSHβ and LHβ) and their regulation by hCG and GnRHa in Japanese sea bass (Lateolabrax japonicas) in vivo.

In this study, three cDNA sequences encoding common glycoprotein α subunit (GTHα), follicle-stimulating hormone β subunit (FSHβ) and luteinizing hormone β subunit (LHβ) were isolated from Japanese sea bass (Lateolabrax japonicas). Comparison of the deduced amino acid sequences with other gonadotropic hormones (GTHs) indicated that their cysteine residues and potential N-linked glycosylation sites were highly conserved, and high homology with those of other perciformes was showed in phylogenetic analysis. GTHs transcripts were present highly in the pituitary and brain and weakly in testis and other tissues. During testicular development, GTHs transcriptional levels in pituitary and brain (expect FSHβ subunit in brain) were significantly increased at spermiation period, stage V. Subsequently, the effects of hCG and GnRHa on the mRNA levels of GTHs subunits were examined. In brain, both hormones were detected to improve the expression of GTHα subunit mRNA. In pituitary, three GTHs subunits increased parallelly and abruptly in two hormone treatment groups. In testis, hCG was suggested to improve three GTHs subunits expression in Japanese sea bass for the first time. These results suggest that both gonadotropins are probably involved in the control of Japanese sea bass spermatogenesis and provide a framework for better understanding of the mechanisms of hormone-mediated reproduction control in Japanese sea bass and other teleosts.