THE MORPHOGENESIS OF MOUSE VALLATE GUSTATORY EPITHELIUM AND TASTE-BUDS REQUIRES BDNF-DEPENDENT TASTE NEURONS

The developmental absence of brain-derived neurotrophic factor (BDNF) in null mutant mice caused three interrelated defects in the vallate g ustatory papilla: sparse innervation, a reduction in the area of the g ustatory epithelium, and fewer taste buds. On postnatal day 7, the stu nted vallate papilla of bdnf null mutant mice was 30% narrower, the tr ench walls 35% reduced in area, and the taste buds 75% less abundant c ompared with wild-type controls. Quantitative assessment of innervatio n density was carried out to determine if the small trench walls and s hortage of taste buds could be secondary consequences of the depletion of gustatory neurons. The diminished gustatory innervation was linear ly associated with a reduced trench wall area (r = + 0.94) and fewer t aste buds (r = + 0.96). Residual taste buds were smaller than normal a nd were innervated by a few surviving taste neurons. We conclude that BDNF-dependent taste neurons contribute to the morphogenesis of Lingua l gustatory epithelia and are necessary for both prenatal and postnata l mammalian taste bud formation. The gustatory system provides a consp icuous example of impaired sense organ morphogenesis that is secondary to sensory neuron depletion by neurotrophin gene null mutation. (C) 1 998 Elsevier Science B.V.