Bitter-sweet victory for taste science
30 Aug 2017 by Evoluted New Media
Research has revealed molecules involved in helping the tongue maintain correct communicate with the brain despite a high turnover of taste cells.
Research has revealed molecules involved in helping the tongue maintain correct communication with the brain despite a high turnover of taste cells.
Human taste buds are located mostly on the upper surface of the tongue. Each taste bud contains 50 to 100 taste cells, containing receptors to detect the five tastes.
Dr Hojoon Lee, from Columbia University and co-author of the study, said: “Most portions of the brain circuits that govern taste are hardwired at birth, except in the tongue, where cells in our taste buds connect to taste neurons. It's a highly dynamic process. Taste cells are replaced every one to three weeks, and one type of receptor may be replaced by a different type. Each time a new taste receptor cell is made, it needs to make the right connection with the brain."
Molecular signals
The research team wanted to understand how correct connections are maintained when there is such as fast and random turnover of taste cells. They hypothesised when receptor cells are produced they express dedicated molecular signals – something they tested by comparing the gene expression of cells that differentiate between bitter and sweet.Dr Lee’s team found these cells differed in their expression of semaphorins, proteins that help create neural circuits. Bitter receptors expressed large amounts of Semaphorin 3A, with Semaphorin 7A expressed by sweet receptors. To discern a link between these molecules and receptor-to-neuron connectivity, mice were genetically engineered to express opposite semaphorins when exposed to bitter or sweet stimuli.
To confirm the receptors in the brain had been rewired, mice whose bitter receptors had been engineered to express Semaphorin 7A were presented with plain and bitter-tasting water. These mice, unlike the control subjects, did not avoid the bitter water.
Professor Charles S. Zuker, co-author also from the University, said: “The taste system gives us a unique opportunity to explore how connections between taste cells and neurons are wired and preserved, in the face of random turnover of our sensory cells. Step-by-step studies like this are helping us decipher the wiring rules of one of our most basic of our senses."
The study, Rewiring the Taste System, can be found in Nature.
