The patch-like pattern of OR37 receptors is formed by turning off gene expression in non-appropriate areas

Olfactory sensory neurons (OSNs) expressing the same odorant receptor (OR) gene are generally widely dispersed throughout the olfactory epithelium (OE). In contrast, OSNs expressing any member from the special OR37 subfamily are concentrated in a small patch in the centre of the OE. To evaluate whether transcription of OR37 genes is only possible in the patch region, or if they can generally be chosen also in non-appropriate areas, a transgenic approach was employed that permanently labelled all cells which ever transcribed a representative OR37 gene. It was found that – in addition to cells inside the patch – numerous cells outside were labelled, indicating that they had transcribed the OR37 gene, but then turned it off while choosing another OR gene. Permanent expression of the OR37 gene was exclusively maintained in the patch. The results suggest that mechanisms acting downstream of an initial OR gene choice restrict OR37 expression to the patch.