| Olfactory sensory neurons (OSNs) mediate the detection of volatile odorants in the main olfactory epithelium (MOE). At some point during OSN development, a single olfactory receptor sequence is chosen from ∼1000 available genes, thus conferring a distinct range of odorant specificity upon each OSN. The molecular mechanisms underlying olfactory receptor choice are poorly understood. However, each olfactory receptor sequence is detected within one of four topographic zones of the MOE, implying a mechanism of spatial patterning.; Olfactory progenitor cells (OPCs) are a dividing cell population that continually gives rise to OSNs and has yet to express olfactory receptors. Although OPC-specific transcriptional regulators like Mash1 are essential for the generation of OSNs, it is likely that additional factors and signaling pathways are involved in OSN specification and the regulation of olfactory receptor choice. The identification of zone-restricted factors in OPCs, in particular, may in turn provide insight into the broader mechanisms of olfactory receptor choice. However, identifying factors expressed specifically by OPCs has been difficult because OPCs are a rare cell population within a highly heterogeneous tissue.; To identify transcripts expressed during OSN development and candidate molecules involved in the spatial patterning of olfactory receptor choice, we have compared the transcriptional profiles of individual cells by microarray hybridization. We validate this approach by demonstrating that microarrays accurately detect cDNA derived from a single cell, and that single-cell cDNA is representative of the original cell transcriptome. With this technique, we identify hundreds of transcriptional differences between mature OSNs and immature OPCs. In addition, we identify factors encoding multiple signaling pathways specifically in OPCs, including several that are expressed independent of Mash1. Finally, we use this approach to isolate numerous zone-restricted transcripts in OSNs, OPCs, and additional novel cell-types. This approach thus affords a comprehensive analysis of olfactory development and reveals candidate factors for regulating olfactory receptor choice by spatial patterning. |
