ACTIVIN IS A NERVE-CELL SURVIVAL MOLECULE

THE structures of five neurotrophic molecules have so far been published. Nerve growth factor1, fibroblast growth factor2, 3 and purpurin4, have been identified as nerve-cell survival molecules. More recently, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor have been cloned and sequenced5, 6. As all these proteins stimulate the survival of ciliary or sensory neurons, a new cell survival assay is required if novel neurotrophic molecules are to be discovered. P19 teratoma cells differentiate to nerve-like cells in the presence of 5 x 107 M retinoic acid (RA)7, 8. But when P19 cells are plated in N2 synthetic medium9 without being exposed to RA, they die within 48 h. In an attempt to identify a molecule(s) that can substitute for RA in promoting P19 survival, we assayed serum-free growth-conditioned media for their ability to promote P19 survival. One cell line from the rat eye secreted a molecule that promoted the survival of P19 cells and some types of nerve cell. We identified this molecule as activin, better known for its role in hormone secretion. © 1990 Nature Publishing Group.