Brain-derived neurotrophic factor is present in diverse taste cell types of adult mice

摘要

Brain-derived neurotrophic factor (BDNF) is present in taste bud primordia in the developing tongue and is thought to be the neurotrophin that supports gustatory innervation during development. However, BDNF continues to be expressed in adult mice and is present in some taste cells (Nosrat et al., 1997. Development, 124: 1333—1342). Since taste cells are constantly renewed throughout adulthood, BDNF may be important for innervation of newly divided taste cells and/or maintaining taste cell innervation. Whether BDNF is present only in newly divided immature taste cells or whether it is present in phenotypically mature cells is unknown. Different taste cell types have been identified based on morphological and immunohistochemical criteria. Morphologically taste cells can be divided into type I (dark) and type II (light) cells; histochemically many different taste cell types exist. Immunohistochemical markers such as anti-blood group H and gustducin are present in type I and type II cells respectively. In addition, gustducin serves as a marker of cytochemically differentiated taste cells at least 3.5 days old (Cho et al., 1998, Chem. Senses, 23: 735—742). To determine which taste cell types express BDNF and whether mature taste cells express BDNF, we have used immunohistochemical markers including ubiquitin-carboxy-terminal hydrolase (PGP 9.5), neural cell ad-hesion molecule (N-CAM), gustducin and anti-blood group H to identify taste cell types in BDNF/aCZ gene targeted ‘knock-in’ mice. In these mice, the BDNF promoter drives beta-galactosidase (n-gal) expression. t3-gal co-localizes with gustducin, PGP 9.5 and N-CAM in various taste cells. Morphologically, long, slender taste cells, as well as pyriform cells, express 13-gal. We conclude that BDNF is present in many elongate taste cells, including differ-entiated type II taste cells, but is absent from basal and edge cells, consistent with the hypothesis that BDNF maintains the innervation of differentiated taste cells.Supported by NIH grant DC00244 to TEE