The bone morphogenetic protein (BMP) is part of the transforming growth factor-beta superfamily. Transforming growth factor-beta (TGF-beta) is a multifunctional peptide that controls proliferation, differentiation and other functions in many cell types. TGF-beta-1 is a peptide of 112 amino acid residues derived by proteolytic cleavage from the C-terminal of a precursor protein.A number of proteins are known to be related to TGF-beta-1 [, ]. Proteins from the TGF-beta family are only active as homo- or heterodimer; the two chains being linked by a single disulphide bond. From X-ray studies of TGF-beta-2 [], it is known that all the other cysteines are involved in intrachain disulphide bonds. As shown in the following schematic representation, there are four disulphide bonds in the TGF-beta's and in inhibin beta chains, while the other members of lack the first bond.BMP-15 (or GDF-9B) has been identified by in the mouse and in humans []. BMP15 protein is encoded by 2 exons []. Homo sapiens (Human) GDF9B transcripts could be detected only in the gonads by RT-PCR analysis, and in situ hybridization studies indicated that GDF9B is not expressed in small primary follicles but rather in the oocytes of late primary follicles []. It was shown that BMP15 is a selective modulator of FSH function []. Male BMP-15 knockout mice are normal and fertile while the females demonstrate decreased ovulation and fertilization rate [].
