Abstract. Bone morphogenetic proteins (BMPs) were originally identified with regard to their actions to regulate ectopic formation of bone and cartilage and early embryonic development. Subsequently, our research program has investigated a BMP system that exists in the mammalian ovary and plays roles in regulating numerous granulosa cell functions. BMP ligands including BMP-2, -4, -6, -7 and -15 were found to inhibit gondotropin-dependent progesterone synthesis by granulosa cells, which led to the hypothesis that BMPs are a physiological luteinization inhibitor in growing ovarian follicles during the follicular phase of the ovarian cycle. The physiological importance of the BMP system for normal mammalian reproduction has been further recognized by the discovery of aberrant reproductive phenotypes of female sheep and humans having mutated genes encoding BMP-15. Physiological roles of BMPs in the pituitary, hypothalamus, adrenal and other tissues have also been discovered. Here we discuss recent advances in the understanding of autocrine/paracrine actions of BMPs in the systemic regulation of endocrine function.Key words: Bone morphogenetic protein, Folliculogenesis, Ovary, Reproduction, Steroidogenesis Bone morphogenetic proteins (BmPs) were originally isolated from bone tissues as proteins that induce bone and cartilage formation in ectopic extra-skeletal sites in vivo [1]. The amino acid sequences from the corresponding cDNAs revealed that BmP ligands are structurally classified into transforming growth factor (TGF)-β superfamily member. To date, more than 30 members of the TGF-β superfamily have been identified in various species [2,3]. There is no direct evidence that all molecules designated as BMPs can induce cartilage and/or bone formation, whereas it has been well established that BMPs regulate multiple biological processes including cell proliferation, apoptosis, differentiation and morphogenesis. in this review, the recent advances regarding critical BmP actions in the ovarian folliculogenesis, which has been mostly discovered by Shimasaki's laboratory [4,5], and in many of extra-gonadal endocrine tissues are introduced.
i) molecular characteristics and receptor signaling of the Bmp systemLigands of the TGF-β superfamily are initially synthesized as large precursor proteins. The precursor proteins dimerize and then are cleaved by proteolytic processing to produce mature dimeric proteins. The BMPs are distinguished from other members by having seven, rather than nine, conserved cysteine residues in the mature region. Six of the seven common cysteines in the mature protein are linked within the subunit to form a rigid structure called a "cysteine knot." The re-