Synapse Formation by Neuroblastoma Hybrid Cells

Abstract

The most widely held hypothesis concerning the mechanism of synapse formation during the last 20 years has been the chemoaffinity hypothesis of Sperry (1963), i.e., that neurons distinguish appropriate from inappropriate synaptic partner cells by interactions between molecules that code for cell recognition. Although Sperry avoided detailed models, many investigators have assumed that neurons or other cells that possess different cell-recognition molecules are generated and that the cells then sort out in appropriate sequences by differential adhesiveness before synaptic connections form. Another quite different hypothesis is that neurons may form relatively stable intercellular attachments during differentiation and that environmental factors and/or transynaptic signals may regulate the expression of genes and thereby determine the final pathway for differentiation and the type of neuron and synapse to be expressed. These hypotheses are not mutually exclusive; both may be involved in the assembly of synaptic circuits.