Growth differentiation factor-3 (GDF3), also known as Vg-related gene 2 (Vgr-2) is protein that in humans is encoded by the GDF3 gene. GDF3 belongs to the transforming growth factor beta (TGF-β) superfamily. It has high similarity to other TGF-β superfamily members including Vg1 (found in frogs) and GDF1. GDF3 is a bi-functional protein that has some intrinsic activity and also modulate other TGF-β superfamily members, e.g. potentiates the activity of NODAL. It may also inhibit other TGF-β superfamily members (i.e. BMPs), thus regulating the balance between different modes of TGF-beta signaling. It has been shown to negatively and positively control differentiation of embryonic stem cells in mice and humans. This molecule plays a role in mesoderm and definitive endoderm formation during the pre-gastrulation stages of development. Expression of GDF3 occurs in ossifying bone during embryonic development and in the brain, thymus, spleen, bone marrow and adipose tissue of adults.