This gene encodes a secreted ligand of the TGF-beta (transforming growth factor-beta) superfamily of proteins. Ligands of this family bind various TGF-beta receptors leading to recruitment and activation of SMAD family transcription factors that regulate gene expression. The encoded preproprotein is proteolytically processed to generate each subunit of the disulfide-linked homodimer. This protein may play a role in the differentiation of tendon cells and spinal cord interneurons. Mice lacking a functional copy of this gene exhibit absence of some spinal dopaminergic neurons and brain defects, male sterility, and premature death. [provided by RefSeq, Sep 2016]