A group of researchers at the University of Southern California studied the perception of sour taste by identifying genes specifically expressed in our sour taste cells using RNA-seq. As the perception for sourness is actually the perception of acidic substances consisting a higher portion of protons, taste cells are proposed to have specialized proton channels in their membrane. Not until recently, by applying whole transcriptome shotgun sequencing, Tu et al. finally identified the gene, Otop 1, responsible for coding a proton-conducting protein and ion channels in taste cells.
To the researchers’ surprise, this gene is also found in our vestibular system. Otop 1 is essential for the formation of otoconia, calcium carbonate crystal structures that sense gravity and acceleration, thus in the inner ear for sensing balance. Further analysis showed that Otop 1 is an evolutionarily conserved gene family that encodes proton-selective ion channels in many different tissue types. The discovery of this gene was the first that linked the vestibular system and taste cells together.