Required for left-right axis determination as a regulator of LEFTY2 and NODAL. By 8.0 dpc, expressed exclusively on the left side of developing embryos with expression predominantly in the prospective floor plate (PFP). Weak expression in the lateral-plate mesoderm (LPM). The processing of the protein may also occur at the second R-X-X-R site located at AA 132-135. Processing appears to be regulated in a cell-type specific manner. Belongs to the TGF-beta family.