Required for posterior mesoderm formation during embryogenesis. Acts indirectly to suppress head formation by altering mesodermal patterning. Also involved in the establishment of left-right axis asymmetry, acting upstream of nodal/nr-1. Can exert long-range effects in the embryo (By similarity). Homodimer; disulfide-linked. Also forms heterodimers with other TGF-beta family members including nodal2/nr-2 and bmp4 (By similarity). Belongs to the TGF-beta family.