Cytoskeleton in the apical region of mouse taste bud cells

The cytoskeletal structures in the apical region of mouse taste bud cells were examined by immunocytochemistry and electron microscopy. Immunostaining for actin showed positive reactions in the apical portions of the taste buds. These regions contained bundles of longitudinally oriented filaments (5-7 nm in diameter) extending from the tip of microvilli to the apical cytoplasm of type I, II, and III cells. After incubation with heavy meromyosin, arrowhead formation was observed along these filaments, thus indicating these filaments to be composed of actin. The plasmalemmal undercoat, which was composed of vertical and horizontal layers, was observed on the zonula occludens. It is supposed that this undercoat gives the structural support for the lateral membrane of the apical region in the taste bud cells.