Cloning of FSHR and expression analysis during the reproductive cycle in female Cynoglossus semilaevis Günther

The complete cDNA sequence of follicle-stimulating hormone receptor( FSHR) gene was cloned by degenerate primer PCR amplification and RACE cDNA amplification for the first time. The length of the cDNA is 3105 bp,and it encodes a protein of about 704 amino acids,which contains the conserved seven transmembrane helix domains( TM helix) ,and it belongs to glycoprotein hormone receptor( GHR) family. Phosphorylation site predictions identified 19 Ser,4 Thr and 5 Tyr potential phosphorylation sites in tongue sole,and only one protein kinase C phosphorylation site( 441T) was predicted. The Clustal X alignment also revealed the presence of specific signature sequences( e. g. 82CCAF,481ERW,594FTD and 667NPFLY) ,which are highly conserved in GpHRs. And comparison with the halibut FSH-R also allowed the identification of 10 imperfect LRRs in the FSHR of Cynoglossus semilaevis. Tissue expression analysis showed that FSHR mRNA is expressed widely in C. semilaevis. Except the high levels in gonads,strong amplification signals were also detected in extragonadal tissues including the spleen,kidney and head kidney. Plasma 17β- Estradiol( E2) seasonal changes are detected by radio immunoassay( RIA) . The result shows that the lowest level appears in April and the highest peak of a year is in October. And we analyzed the relative expression level of FSHR in reproductive cycle of female. There is the highest level in October and the lowest level in January.