Growth and Differentiation Factor 1 (GDF-1) is a 12 - 15 kDa secreted protein in the TGF-beta superfamily. It is the functional equivalent of frog, zebrafish, and chick Vg1. GDF-1 is expressed in the developing and adult nervous system, particularly in neurons of the cerebral cortex and hippocampus. It is required during embryogenesis for development of left/right axis asymmetry, anterior/posterior axis asymmetry, and the notochord. It cooperates with Nodal and GDF-3 in these activities and potentiates Nodal bioactivity through formation of a 27 kDa noncovalent GDF-1-Nodal heterodimer. The presence of Nodal is required for GDF-1 induced effects. GDF-1 signals through heteromeric receptor complexes containing Activin RIIA or Activin RIIB, ALK4 or ALK7, and an EGF-CFC protein such as Cryptic or Cripto. Loss of function mutations in GDF-1 are associated with a variety of human cardiac development defects.