Olfactory sensory neurons are believed to follow a 'one-neuron-one-receptor' rule to properly translate odor signals into the brain. However, the complexity of the olfactory system—which displays continuous neurogenesis, with more than 1,000 olfactory receptor genes expressed in several developmental stages—has limited detailed analyses. Two studies now report the application of single-cell transcriptomics of mouse olfactory epithelium to investigate this system. Hanchate et al. and Tan et al. first used genetic markers to assign cells to different developmental stages. Separately, they examined olfactory receptor expression, with Hanchate et al. finding that this began to appear in precursor neurons and was well established in the immature neurons. Tan et al. noted that some cells expressed multiple splicing isoforms of the same receptors, and identified new isoforms. Furthermore, both studies reported coexpression of multiple distinct olfactory receptors in a subset of cells, primarily immature neurons. Initial analysis of tissue sections confirmed that these observations were not an artifact of cell handling. Finally, Hanchate et al. determined that olfactory receptor expression does seem to be linked to the identity of receptors expressed in the same nasal zone, but not to receptor-induced neuronal activity. Tan et al. extended the conclusion to a related gene family that senses volatile amines. Further work will be needed to determine which of several proposed mechanisms leads to the 'one-neuron-one-receptor' phenotype.
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Goodman, C. Tracking the scent. Nat Chem Biol 12, 53 (2016). https://doi.org/10.1038/nchembio.2011