Tissue and zonal-specific expression of an olfactory receptor transgene.

Discrimination of odorants is thought to arise from the selective expression of one of a small number of individual receptors in any single olfactory neuron. Receptor genes are expressed in a small subset of neurons throughout a zonally restricted region of the sensory epithelium. We demonstrate that a 6.7 kb region upstream of the M4 olfactory receptor coding region was sufficient to direct expression in olfactory epithelium. Moreover, reporter expression recapitulated the zonal restriction and distributed neuronal expression observed for endogenous olfactory receptors. Transgenic lines were obtained that directed expression in two different receptor zones, one of which was identical to the endogenous M4 receptor. When the reporter was expressed in the same zone as the endogenous M4 receptor, the two expression patterns were, in large part, nonoverlapping. These results suggest a model in which important regulatory elements are located in close proximity to transcription initiation sites of the olfactory receptor genes and receive information defining zonal patterning via long-range processes.