Cloning of FSH-β, LH-β and glycoprotein hormone α subunits in pejerrey Odontesthes bonariensis (Valenciennes): expression profile and relationship with GnRH expression and plasma sex steroid levels in male fish

Three cDNAs encoding pejerrey Odontesthes bonariensis follicle stimulating hormone-β (FSH-β), luteinizing hormone-β (LH-β) and glycoprotein-α (GPH-α) subunits were cloned and characterized. Gene expression of these subunits was analysed by real-time polymerase chain reaction (PCR) and compared with the brain gene expression of endogenous gonadotropin-releasing hormones (GnRHs): Pacific salmon GnRH (GnRH-III), pejerrey GnRH (GnRH-I) and chicken GnRH-II (GnRH-II) and plasma sex steroid levels in adult males. The nucleotide sequences of the FSH-β, LH-β and GPH-α subunits are 466, 558 and 677 base pairs long, encoding for mature peptides of 102, 118 and 98 amino acids respectively. Maturing males had high expression of FSH-β and GPH-α subunits, and intermediate levels of LH-β when compared with running ripe and spent stages. These animals had the lowest plasma testosterone (T) and 11-ketosterone (11-KT) values as well as low expression of sGnRH, cGnRH-II and pjGnRH. Running ripe males had the lowest expression of FSH-β and the highest expression of LH-β and GPH-α subunits, and of the three GnRH genes. At this stage, the highest values of T and 11-KT were observed. Spent males showed low expression of the three gonadotropin (GtH) subunits, sGnRH, pjGnRH and low levels of T. At this stage, 11-KT levels and cGnRH-II expression showed a tendency to decrease but the values were not statistically significant ( P < 0·05) to running ripe stage. The present results would suggest that T and 11-KT modulate the expression of the FSH subunits. The expression of the anterior brain GnRH variants, sGnRH and pjGnRH is correlated with LH-β expression and reinforce the importance of the forebrain GnRH variants on the regulation of pituitary function.