Olfactory expression of trace amine-associated receptors requires cooperative cis-acting enhancers

Ami Shah,Madison Ratkowski,Alessandro Rosa,Thomas Bozza,Paul Feinstein

doi:10.1038/s41467-021-23824-3

Abstract

Olfactory sensory neurons express a large family of odorant receptors (ORs) and a small family of trace amine-associated receptors (TAARs). While both families are subject to so-called singular expression (expression of one allele of one gene), the mechanisms underlying TAAR gene choice remain obscure. Here, we report the identification of two conserved sequence elements in the mouse TAAR cluster (T-elements) that are required for TAAR gene expression. We observed that cell-type-specific expression of a TAAR-derived transgene required either T-element. Moreover, deleting either element reduced or abolished expression of a subset of TAAR genes, while deleting both elements abolished olfactory expression of all TAARs in cis with the mutation. The T-elements exhibit several features of known OR enhancers but also contain highly conserved, unique sequence motifs. Our data demonstrate that TAAR gene expression requires two cooperative cis-acting enhancers and suggest that ORs and TAARs share similar mechanisms of singular expression.

Highlights

Olfactory sensory neurons express a large family of odorant receptors (ORs) and a small family of trace amine-associated receptors (TAARs)
To begin defining the minimal promoter sequences required for TAAR gene expression, we generated a TAAR4 transgene consisting of a genomic fragment encompassing ~2.3 kb upstream of the Taar[4] transcription start site, the single intron, and the endogenous polyadenylation site (Fig. 1a)
The resulting transgene (ΔT4-YFPtg) failed to be expressed in 5 independent founder lines (Fig. 1b, c). This suggested that the included putative promoter was insufficient to impart gene choice, or that the transgene was otherwise non-functional

Summary

Introduction

Olfactory sensory neurons express a large family of odorant receptors (ORs) and a small family of trace amine-associated receptors (TAARs). While both families are subject to socalled singular expression (expression of one allele of one gene), the mechanisms underlying TAAR gene choice remain obscure. Our data demonstrate that TAAR gene expression requires two cooperative cis-acting enhancers and suggest that ORs and TAARs share similar mechanisms of singular expression. Since the discovery of H, scores of similar enhancers have been identified scattered in and around OR gene clusters[16,17,18,19,20,21] These include the P element in the P2 (Olfr17) cluster, the A/J-core element in the class I OR cluster[20,22] and the large set of Greek Islands[19,21]

Methods

Results

Conclusion