Secreted signal that acts globally to regulate anterior/posterior axial patterning during development (PubMed:10391213). May play critical roles in patterning both mesodermal and neural tissues (PubMed:10391213). It is required for proper vertebral patterning and orofacial development (By similarity). Signals through activin receptors type-2, ACVR2A and ACVR2B, and activin receptors type-1, ACVR1B, ACVR1C and TGFBR1 leading to the phosphorylation of SMAD2 and SMAD3 (PubMed:16845371, PubMed:12414726). Homodimer; disulfide-linked (By similarity). Interacts directly with ACVR2B (PubMed:16845371, PubMed:12414726). Interacts directly with ACVR2A (PubMed:12414726). Interacts with ACVR1B, TGFBR1 and ACVR1C in an ACVR2B-dependent manner (PubMed:16845371). Interacts with FST isoform 2/FS288 (By similarity). Highly expressed in the developing limb bud, initially detected in the distal mesenchyme, and later localizing to regions around the developing bones. Is also expressed in adult dental pulp and brain. First strongly expressed in restricted domains at 8.5 dpc where it is highest in the tail bud. At 10.5 dpc, expressed in the branchial arches, limb bud, tail bud and posterior dorsal neural tube. Later, expressed in terminally-differentiated odontoblasts, the nasal epithelium, retina and specific regions of the brain. Synthesized as large precursor molecule that undergoes proteolytic cleavage by furin-like proteases (By similarity). This produces an inactive form consisting of the mature C-terminal portion non-covalently bound to its cleaved N-terminal propeptide. Activation of the mature form requires additional cleavage of the propeptide by a tolloid-like metalloproteinase. Deficient mice die neonatally showing altered patterning of the axial skeleton and impaired renal, palate, stomach, spleen and pancreatic development. Belongs to the TGF-beta family.