The neural differentiation gene Mash-1 has a distinct pattern of expression from the taste reception-related genes gustducin and T1R2 in the taste buds

Taste bud cells have a limited lifespan and are continuously replaced just like other epithelial cells. Although there is some evidence that taste buds may arise from the local epithelium, taste receptor cells have neuronal properties. This implies that there must be a critical stage at which the epithelial precursor cells for taste receptor cells start to exhibit neural properties during the differentiation of the taste receptor cells. The expression of the neural-specific transcription factors Mash-1 and Prox-1 in the nervous system is transient and precedes neuronal differentiation. Therefore, we examined the expression of Mash-1 and Prox-1 in the epithelium of circumvallate papillae of the tongue in order to clarify the localization of the precursor cells with neural properties and observed that both expressions are restricted to the taste buds. Two-colour in situ hybridization showed that the signals for Mash-1 did not overlap those for taste receptor cell-specific genes such as gustducin and T1R2. In the process of development and regeneration of the taste buds, the expression of Mash-1 preceded that of gustducin and T1R2. These observations suggest that Mash-1 could be a candidate for a marker of immature taste receptor cells, including the cells that express gustducin and/or T1R2 at a later stage.