Activin B, a TGF-beta superfamily member, has a wide range of biological activities. It is involved in mesoderm induction, neural cell differentiation, bone remodeling, hematopoiesis, and reproduction physiology. Produced as a precursor protein, it is cleaved to release the carboxy-terminal bioactive ligand. Activin B binds directly to Act RII and the complex then associates with Act RI to initiate signaling. The human Activin B amino acid sequence is greater than 98% identical to the mouse sequence.
Netrin-2 is a laminin-like axon guidance molecule that both attracts and repels growing axons during development. These actions are mediated by specific receptor complexes containing either DCC (deleted in colorectal carcinoma) or neogenin, in the case of attractant, or UNC-5-related proteins, in the case of repellent actions. Netrin-2 is conserved among C. elegans, Drosophila, and vertebrates.