Expression of three gonadotropin subunits in Southern catfish gonad and their possible roles during early gonadal development

The three gonadotropin (GtH) subunit cDNAs, GtHα, FSHβ and LHβ, which contain complete open reading frames were isolated from Southern catfish (Silurus meridionalis Chen) ovary. RT-PCR revealed that GtHα, FSHβ and LHβ mRNA were expressed in ovary, female and male pituitaries, but not in testis. Ontogeny study showed that GtHα and FSHβ expressed in ovary from 25 dah (days after hatching) and LHβ expressed from 40 dah onwards. The expression levels of these genes in all-female Southern catfish gonad were down-regulated after treatment with tamoxifen from 5 to 25 dah when measured at 65 dah. These results indicated the involvement of the three subunits in gonadal development and sexual differentiation.