Axonal projection of olfactory sensory neurons during the developmental and regeneration processes

We have studied the projection of olfactory sensory neurons (OSNs), during the developmental and regeneration processes, using the transgenic mouse carrying the differently tagged odorant receptor genes, MOR28. We have found that the axon terminals of the two sets of MOR28-positive OSNs, one expressing the lacZ tag and the other expressing the green fluorescent protein gene, are dispersed and intermingled at early developmental or regeneration stages. Projection areas become more distinct and separated at later stages, however, two sets of axon fibers are not typically bundled or segregated during pathfinding. It appears that segregation of axons mainly occurs when they target at the olfactory bulb to form the glomerular structure.