Regulation of Dorsal Root Ganglia Proteins and Genes During Early Development and Synaptogenesis

Abstract

Neurons of the dorsal root ganglia derive from neural crest precursor cells. Shortly after arrival of neural crest precursors to the coalescing ganglia, neurons are “born” as the cells undergo their final mitosis, generating first the large and then small diameter populations of DRG neurons. By about embryonic day 15 these neurons have extended processes to the spinal cord. The first evidence for synaptic interaction between dorsal root ganglia and spinal cord neurons begins about embryonic day 17. Significant maturation of the synapses occurs subsequently and continues through birth, with progressively larger areas of synaptic contact and increased numbers of presynaptic vesicles (Lawson et al. 1974). We have been interested in determining the molecules involved in these transitions, as neuronal precursor becomes post-mitotic neuron, and then as it ceases growth cone exploration and makes stable and specific synapses. We have used two techniques to isolate such molecules. First, we have determined proteins transported to synaptic regions prior to and after synapse formation. Second, we have established cDNA libraries from critical stages during development and have compared gene expression using the technique of differential hybridization to search for stage-specific cDNA’s. We have been especially interested in those molecules that characterize precursor and early embryonic states and diminish during maturation.