Results indicate that these factors have several different roles in directing neuronal differentiation and function, including effects on adult neuronal morphology and function. A second project seeks to characterize adhesion-promoting molecules important in regulating axon growth and targeting. The laboratory has identified several molecules that are important in vitro and is beginning to study their functions in vivo. We are also interested in understanding mechanisms by which adhesive interactions between growth cones and molecules in their environment result in enhancement or inhibition of axonal growth. A final project examines the roles of cell surface and extracellular matrix molecules in directing the formation of synapses.
Neurotrophic factors are proteins which function to regulate survival of neurons.
Thus, in certain circumstances, NT-3 can activate each of the three trk receptors in vivo and has the properties expected of a survival factor that provides transient support for newly born neurons before their axons contact their final targets. In contrast, using a similar lacZ reporter, NT-3 is strongly expressed during this period in mesenchymal cells adjacent to the ganglia, but expression is lost as the mesenchyme further differentiates. As NT-3 plays a very general, but transient role in sensory ganglia genesis, it is critical to understand its regulation. In the last report, it was suggested that release by neurons of neuregulins was important in regulating the expression of NT-3. Analyses of sensory neuron and precursor pools in the NGF and NT-3 mutants has indicated that loss of neurons results in premature conversion of precursors to neurons, reducing indirectly the numbers of neurons of all types ultimately generated.