Growth factor of the TGF-beta superfamily that plays important role in various biological processes, including spermatogenesis, osteogenesis, steroidogenesis as well as regulation of energy balance (PubMed:9463357, PubMed:12925636, PubMed:28465413). Initiates the canonical BMP signaling cascade by associating with type I receptor BMPR1A and type II receptor BMPR2. Once all three components are bound together in a complex at the cell surface, BMPR2 phosphorylates and activates BMPR1A (By similarity). In turn, BMPR1A propagates signal by phosphorylating SMAD1/5/8 that travel to the nucleus and act as activators and repressors of transcription of target genes. In addition, activates the SMAD2/3 pathway (PubMed:28465413). Homodimer; disulfide-linked. Expressed in testis. expressed in trophoblast cells of the labyrinthine region of the placenta and in the inner root sheath of hair follicles of early postnatal skin (PubMed:8843393). Expressed predominantly in the neonatal mouse spermatogonia (PubMed:28465413). Extensive expression found in 8-day embryos, fell drastically in 10-day embryos and virtually absent in 17-day embryos. Expressed during specific stages of spermatogenesis, with the highest levels in stage 6-8 round spermatids after 3 weeks of age. By dexamethasone in calvarial osteoblasts. Deletion mutant mice show normal embryonic and postnatal development. Homozygous mutant females have normal fertility. Males do not show germ cell defects during the initiation of spermatogenesis. However, germ cell degeneration is observed in about half of adult males. Belongs to the TGF-beta family.