The “One Neuron–One Receptor” Rule in the Physiology and Genetics of Olfaction

摘要

The phenomenal sensitivity of the olfactory system and its ability to detect an enormous diversity of olfactory stimuli are to a large extent due to the existence of numerous olfactory receptors. The genes encoding olfactory receptors (OR) form the largest family in mammalian genomes. The defining principle in the model of olfactory information encoding is the “one neuron–one receptor” rule, whereby just one gene of the OR gene family is selected for expression in each of the 107 olfactory neurons located in the olfactory epithelium. Although the physiological appropriateness of the “one neuron–one receptor” principle is undoubted, the rule is essentially hypothetical in nature and has not been verified experimentally to the necessary level. In particular, the question of the epigenetic mechanisms of stochastic, monogenic, and monoallelic expression of OR genes remains open. The results of deep sequencing of the transcriptomes of single cells unexpectedly revealed multireceptor neurons containing transcripts for several OR genes. Does this mean that the rule which more than 25 years ago was believed to be physiologically confirmed, unshakeable, and unarguable does not operate? This review will present different interpretations of results from studies of the transcriptomes of single olfactory neurons which explain the existence of “multireceptor” neurons and their role in the process of olfactory neurogenesis.