YAC transgene-mediated olfactory receptor gene choice.

In the mouse, individual olfactory neurons express one of a thousand distinct olfactory receptor genes. Furthermore, only one allele of the expressed gene is transcribed. This phenomenon, random allelic inactivation, along with the observation that the olfactory receptor genes reside in large chromosomal arrays, suggests a role for long-range gene regulation in olfactory receptor gene choice. We have constructed a 300-kb yeast artificial chromosome (YAC) transgene in which a single receptor gene is marked while maintaining its coding region. This 300-kb piece of DNA functions as an independent olfactory receptor gene locus in directing olfactory receptor gene choice in both the olfactory system and the accessory olfactory system (vomeronasal organ, VNO). Furthermore, the transgene, like endogenous olfactory receptor loci, is subject to allelic inactivation.