NETRIN AND NETRIN RECEPTOR EXPRESSION IN THE EMBRYONIC MAMMALIAN NERVOUS-SYSTEM SUGGESTS ROLES IN RETINAL, STRIATAL, NIGRAL, AND CEREBELLARDEVELOPMENT

The netrins are laminin-like axon guidance molecules that are conserve d among Caenorhabditis elegans, Drosophila, and vertebrates and that h ave chemoattractive and chemorepellant properties. To study the possib le actions of this gene family in the developing and adult mammalian n ervous systems, we have cloned a partial cDNA which corresponds to a r egion conserved among chick netrin-1, netrin-2, and unc-6 and studied its expression and that of a netrin receptor, dec, the deleted in colo rectal cancer gene, in the developing and adult rat CNS. The localizat ion of cells expressing netrin or dec suggests that these genes, in ad dition to their actions in defining the ventral midline, may act in co ntrolling retinal ganglion cell axon guidance in the optic nerve, cell migration in the developing cerebellum and olfactory epithelium, and development and maintenance of connections to the substantia nigra and corpus striatum.