Taste receptor cells in the tongue are epithelial in nature and turnover frequently. Taste receptor cell-associated neurons carrying bitter, sweet, or sour signals never turnover and are hardwired to specific gustatory centers in the brain. How can ever-changing bitter or sweet receptors find never-changing neurons that must match the specificity of the signal? This article reviews a recent paper published in Nature (Lee, MacPherson, Parada, Zuker, & Ryba, 548:330-333) that identified two molecules belonging to the semaphorin axon guidance family of molecules (SEMA3A and SEMA7A) that help maintain the “labeled line principle” between peripheral bitter or sweet receptors and their respective central projection area in the gustatory center.
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