ODORANT RECEPTORS GOVERN THE FORMATION OF A PRECISE TOPOGRAPHIC MAP

Olfactory neurons expressing a given odorant receptor project with pre cision to 2 of the 1800 glomeruli within the olfactory bulb to create a topographic map of odor quality. We demonstrate that deletions or no nsense mutations in the P2 odorant receptor gene cause the axons of th ese cells to wander rather than converge on a specific glomerulus. Rec eptor substitution experiments that replace the P2 gene with the codin g region of the P3 gene result in the projection of P3-->P2 axons to a glomerulus touching the wildtype P3 glomerulus. These data, along wit h additional receptor substitutions, indicate that the odorant recepto r plays an instructive role in the establishment of the topographic ma p.