DISTINCT ROLES OF SYNAPSIN-I AND SYNAPSIN-II DURING NEURONAL DEVELOPMENT

The synapsins are a family of neuron-specific proteins, associated wit h the cytoplasmic surface of synaptic vesicles. which have been shown to regulate neurotransmitter release in mature synapses and to acceler ate development of the nervous system. Using neuronal cultures from mi ce lacking synapsin I, synapsin IT, or both synapsins I and It, we hav e now found that synapsin I and synapsin II play distinct roles in neu ronal development. Deletion of synapsin II, but not synapsin I, greatl y retarded axon formation. Conversely, deletion of synapsin I but not synapsin LI, greatly retarded synapse formation. Remarkably, the delet ion of both synapsis led to partial restoration of the wild phenotype. The results suggest that the synapsins play separate but coordinated developmental roles.