RETROGRADE NEUROTROPHIN-MEDIATED CONTROL OF NEURON SURVIVAL IN THE DEVELOPING CENTRAL-NERVOUS-SYSTEM

NEURONAL death in vertebrate development is widely believed to be regu lated by retrograde survival signals from the axonal target territory, and these signals are assumed to be initiated by the binding of troph ic molecules to the axon terminal. However, direct evidence for the re trograde transmission of such survival signals along developing axons is only available in the peripheral nervous system. We show here in a central projection, the isthmo-optic projection of chick embryos, that a neurotrophin, brain-derived neuro-trophic factor, can indeed initia te retrograde survival signals from the target territory. A related mo lecule, neurotrophin-3, is ineffective.