Activins are dimeric growth and differentiation factors which belong to the transforming growth factor-beta (TGF-beta) superfamily of structurally related signaling proteins. Activins have a wide range of biological activities including mesoderm induction, neural cell differentiation, bone remodeling, hematopoiesis, and reproductive physiology. Activins are also involved in growth and differentiation of several tissues from different species.
Type II receptors are considered to be constitutively active kinases. Activin has been suggested to be an autocrine/paracrine regulator in the human placenta. The presence of ACVR2 mRNA has been demonstrated in human trophoblast cells and there is also evidence of expression of the gene in human brain and ovary.