Molecular characterization of Chinese sturgeon gonadotropins and cellular distribution in pituitaries of mature and immature individuals

Chinese sturgeon (Acipenser sinensis) is a rare and endangered species, and also an important resource for the sturgeon aquaculture industry. To understand molecular characterization of Chinese sturgeon gonadotropins (GTHs), we cloned the full-length cDNAs of gonadotropin subunits common α (GTH-α), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from a pituitary cDNA library of mature female. Two subtypes of GTH-α were identified. The nucleotide sequences of A. sinensis common α I (AsGTH-α I), common α II (AsGTH-α II), FSHβ (AsFSHβ) and LHβ (AsLHβ) subunit cDNAs are 345, 363, 387 and 414 bp in length, and encode mature peptides of 115, 121, 129 and 138 aa, respectively. Then, three polyclonal antibodies were prepared from the in vitro expressed AsGTH-α I, AsFSHβ and AsLHβ mature proteins, respectively. Significant expression differences were revealed between immature and mature sturgeon pituitaries. Western blot detection and immunofluoresence localization revealed the existence of three-gonadotropin subunits (AsGTH-α, AsFSHβ and AsLHβ) in mature sturgeon pituitaries, but only AsFSHβ was detected in immature individual pituitaries during early stages in the sturgeon life, and obvious difference was observed between males and females. In males, AsFSHβ was expressed in 4-year-old individuals, whereas in females, AsFSHβ was just expressed in 5-year-old individuals.