Transforming growth factor-beta 3, glial cell line-derived neurotrophic factor, and fibroblast growth factor-2, act in different manners to promote motoneuron survival in vitro

Developing chick motoneurons depend on as yet unidentified factors from the periphery and the central nervous system for their survival. Using cultures of purified embryonic motoneurons, we show that basic fibroblast growth factor (FGF-2) or transforming growth factor-beta 3 (TGF beta 3) each have only low survival-promoting activity when tested alone, but act synergistically to keep motoneurons alive for at least 3 days. Glial cell line-derived neurotrophic factor (GDNF), another member of the TGF beta family, was itself sufficient to maintain a population of motoneurons. However, its effect was not significantly increased by the addition of FGF-2. These results suggest that FGF-2, TGF beta 3, and GDNF, which are all present in the environment of developing motoneurons, may act different mechanisms as physiological survival factors for this population of central neurons.