Netrin Inhibits Regenerative Axon Growth of Adult Dorsal Root Ganglion Neurons in Vitro

Netrin is a neuronal guidance molecule implicated in the development of spinal commissural neurons and cortical neurons. The attractive function of netrin requires the receptor, Deleted in Colorectal Cancer (DCC), while the receptor Unc5h is involved in the repulsive action of netrin during embryonic development. Although the expression of netrin and its receptor has been demonstrated in the adult nervous system, the function of netrin in adult neurons has not yet been elucidated. Here, we show that netrin treatment inhibited neurite outgrowth of adult dorsal root ganglion (DRG) neurons in explant and dissociated cultures. In addition, unc5h1-3 mRNAs, but not the dcc mRNA, are abundantly expressed in the adult DRG. An in situ hybridization study demonstrated that unc5h mRNAs were expressed in DRG neurons. This finding indicates that netrin/Unc5h signaling may play a role in the neurite outgrowth of adult DRG neurons and that netrin may be involved in the regulation of peripheral nerve regeneration.