Characterization of bmp15 and its regulation by human chorionic gonadotropin in the follicle of gibel carp (Carassius auratus gibelio)

Bone morphogenetic protein (BMP15) is a member of the transforming growth factor beta (TGF-beta) superfamily with a key role in regulating follicle development in mammals and birds. However, potential ovarian roles of BMPs remain unexplored in teleosts. In this study, the full-length sequences of bmpl5 were obtained using rapid-amplification of cDNA ends (RACE). The full-length cDNA sequence of bmpl5 is 2217 bp which contained 214 bp 5'-UTR and 845 bp 3'-UTR. The open reading frame (ORF) sequence of bmpl5 is 1158 bp, encoding a predicted protein of 385 amino acid residues. BMP15 has a specific RXXR protease cleavage site of TGF-beta superfamily (is RIRR) and six conserved cysteine residues. Using real-time quantitative PCR revealed that bmpl5 mRNA was largely expressed in the ovary and testis and mostly in oocytes within the follicle, slightly expressed in muscle, liver and pituitary. BMP15 is mainly present at stage I follicles by real-time quantitative PCR and immunohistochemistry. Phylogenetic analysis showed that gibel carp bmpl5 was similar to bmpl5 of zebrafish and other fish species. Treatment with human chorionic gonadotropin (hCG) in isolated follicles of gibel carp in vitro showed altered bmpl5 mRNA expression: when treated with 10 ng/mL hCG for 10 h, the expression level of bmp15 was significantly increased. However, with proceeding cultivation, the expression level of BMP15 mRNA decreased. The results of this study indicate that bmp15 may play a key role during development of follicles in gibel carp, especially in early stage follicles. (C) 2012 Elsevier Inc. All rights reserved.