Olfr603, an orphan olfactory receptor, is expressed in multiple specific embryonic tissues

• Olfr603 is one of 1200 G protein-coupled receptors classified as an olfactory receptor.
• The function of Olfr603 is unknown.
• Olfr603 is widely expressed within a number of embryonic tissues.
• Sites of expression include the neural tube, neural crest, heart and eye.
• This widespread non-olfactory expression suggests a role in early embryonic development.

BackgroundOlfactory receptors were initially believed to be expressed specifically within the olfactory neurons. However, accumulating genome-scale data has recently demonstrated more extensive expression. There are hundreds of olfactory receptor family members and the realisation of their widespread expression provides an opportunity to reveal new biology. However, existing data is predominantly based on RT-PCR, microarray and RNA-seq approaches and the details of tissue and cell-type specific expression are lacking.ResultsAs a proof of principle, we selected Olfr603 for expression analysis. We generated an antibody against a non-conserved epitope of Olfr603 and characterised its expression in E8.5-E12.5 mouse embryos using immunohistochemistry. This analysis demonstrated a dynamic pattern of expression in diverse cell types within the developing embryo unrelated to the olfactory system. Expression was detected in migrating neural crest, endothelial precursors and vascular endothelium, endocardial cells, smooth muscle, neuroepithelium and within the ocular tissues. This complex distribution does not conform to any apparent germ layer or tissue origin.ConclusionsThis initial characterisation of Olfr603 expression highlights the potential for a broad role for this receptor in the development of many tissues.