Growth factor of the TGF-beta superfamily that plays essential roles in many developmental processes including cartilage and bone formation (PubMed:31019025). Also plays an important role in the regulation of iron metabolism by acting as a ligand for hemojuvelin/HJV (By similarity). Initiates the canonical BMP signaling cascade by associating with type I receptor ACVR1 and type II receptor ACVR2B (PubMed:18070108). In turn, ACVR1 propagates signal by phosphorylating SMAD1/5/8 that travel to the nucleus and act as activators and repressors of transcription of target. Can also signal through non-canonical pathway such as TAZ-Hippo signaling cascade to modulate VEGF signaling by regulating VEGFR2 expression (PubMed:33021694). Interacts with SOSTDC1 (By similarity). Interacts (when glycosylated) with type I receptor ACVR1 (PubMed:18070108). Interacts with type II receptor ACVR2B (PubMed:18070108). Interacts with Hemojuvelin/HJV (By similarity). Glycosylated at Asn-454. Glycosylation is crucial for recognition by the activin receptor type I/ACVR1. Belongs to the TGF-beta family. Bone morphogenetic protein 6 entry