Different expression domains for two closely related amphibian TAARs generate a bimodal distribution similar to neuronal responses to amine odors.

Adnan S Syed,Shahrzad Bozorg Nia,Sigrun I Korsching,Ivan Manzini,Alfredo Sansone,Sebastian Röner

doi:10.1038/srep13935

Abstract

Olfactory perception is mediated by a multitude of olfactory receptors, whose expression in the sensory surface, the olfactory epithelium, is spatially regulated. A common theme is the segregation of different olfactory receptors in different expression domains, which in turn leads to corresponding segregation in the neuronal responses to different odor groups. The amphibian olfactory receptor gene family of trace amine associated receptors, in short TAARs, is exceedingly small and allows a comprehensive analysis of spatial expression patterns, as well as a comparison with neuronal responses to the expected ligands for this receptor family, amines. Here we report that TAAR4b exhibits a spatial expression pattern characteristically different in two dimensions from that of TAAR4a, its close homolog. Together, these two genes result in a bimodal distribution resembling that of amine responses as visualized by calcium imaging. A stringent quantitative analysis suggests the involvement of additional olfactory receptors in amphibian responses to amine odors.

Highlights

Olfactory perception is mediated by a multitude of olfactory receptors, whose expression in the sensory surface, the olfactory epithelium, is spatially regulated
We show that amine-responsive cells follow a bimodal spatial pattern that could be partially explained by the spatial expression pattern of taar4a and taar4b genes
The taar gene family of Xenopus tropicalis has been predicted to consist of just 3 genes, TAAR1, TAAR4a and TAAR4b10

Summary

Introduction

Olfactory perception is mediated by a multitude of olfactory receptors, whose expression in the sensory surface, the olfactory epithelium, is spatially regulated. We report that TAAR4b exhibits a spatial expression pattern characteristically different in two dimensions from that of TAAR4a, its close homolog Together, these two genes result in a bimodal distribution resembling that of amine responses as visualized by calcium imaging. The amphibian main olfactory epithelium (MOE) still contains a large number of microvillous sensory neurons, in addition to ciliated sensory neurons[1] These two sensory neuron populations are to some extent segregated within the MOE2–4, resulting in corresponding inhomogeneities of the olfactory receptors, since the olfactory receptor gene families expressed in microvillous neurons are different from those found in ciliated neurons[2,5]. Our results are consistent with taar genes possessing their own unique expression zones, and possibly mediating amine responses, and point to the existence of additional amine receptors in amphibian olfaction

Methods

Results

Conclusion