Expression profile of ectopic olfactory receptors determined by deep sequencing

PLoS One. 2013;8(2):e55368. doi: 10.1371/journal.pone.0055368. Epub 2013 Feb 6.

Abstract

Olfactory receptors (ORs) provide the molecular basis for the detection of volatile odorant molecules by olfactory sensory neurons. The OR supergene family encodes G-protein coupled proteins that belong to the seven-transmembrane-domain receptor family. It was initially postulated that ORs are exclusively expressed in the olfactory epithelium. However, recent studies have demonstrated ectopic expression of some ORs in a variety of other tissues. In the present study, we conducted a comprehensive expression analysis of ORs using an extended panel of human tissues. This analysis made use of recent dramatic technical developments of the so-called Next Generation Sequencing (NGS) technique, which encouraged us to use open access data for the first comprehensive RNA-Seq expression analysis of ectopically expressed ORs in multiple human tissues. We analyzed mRNA-Seq data obtained by Illumina sequencing of 16 human tissues available from Illumina Body Map project 2.0 and from an additional study of OR expression in testis. At least some ORs were expressed in all the tissues analyzed. In several tissues, we could detect broadly expressed ORs such as OR2W3 and OR51E1. We also identified ORs that showed exclusive expression in one investigated tissue, such as OR4N4 in testis. For some ORs, the coding exon was found to be part of a transcript of upstream genes. In total, 111 of 400 OR genes were expressed with an FPKM (fragments per kilobase of exon per million fragments mapped) higher than 0.1 in at least one tissue. For several ORs, mRNA expression was verified by RT-PCR. Our results support the idea that ORs are broadly expressed in a variety of tissues and provide the basis for further functional studies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Exons
  • Female
  • Gene Expression Profiling / methods
  • High-Throughput Nucleotide Sequencing / methods*
  • Humans
  • Middle Aged
  • Olfactory Receptor Neurons / metabolism*
  • Pseudogenes
  • RNA, Messenger / genetics
  • Receptors, Odorant / genetics*
  • Signal Transduction
  • Smell / genetics
  • Transcriptome

Substances

  • RNA, Messenger
  • Receptors, Odorant

Grant support

Caroline Flegel was funded by the Heinrich und Alma Vogelsang Stiftung. Hanns Hatt was funded by the DFG-Sonderforschungsbereich 642 “GTP- and ATP dependent membrane processes”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscripts.