Fig. 4. Amphiphysin is localized to the apical membrane domain of epithelial and neural cell types. (A-D) Lateral views of a developmental time series of a stage 5 embryo stained for Amph. At early stage 5, the syncitial nuclei have migrated to the periphery and the membrane has begun to invaginate between the nuclei. Amph is first localized to the apical surface and migrates basally as the membrane extends inwards during cellularization. (D) Upon the completion of cellularization at the end of stage 5, Amph is again localized apically. (E-H) Double labels of Amph and Bifocal protein localization during early cellularization (E,G) and after completion of cellularization (F,H). Amph protein (E,F) is enriched at the invaginating membrane during cellularization, whereas Bifocal protein (G,H) remains localized to the apical membrane domain. (I) Amph is apical in ectoderm and neuroblasts. Lateral view of a stage 9 embryo showing apical Amph in the ventral ectoderm and in neuroblasts (arrows). (J) Lateral view of a stage 16 embryo to emphasize that Amph is not detected in the embryonic CNS (bottom left panel) when compared with the staining in the epidermis and trachea (top panel) and hindgut (bottom right panel). (K,L) Amph is detected at the apical (lumenal) membrane of tracheal tubules and of the esophagus. (K) Stage 15 embryo showing Amph expression at the apical surface in mature tracheal tubules. (L) Stage 15 embryo showing Amph expression in the esophagus. In addition, the non-epithelial secretory garland cells flanking the esophagus also express Amph. (M,N) Amph is localized to apical membrane and vesicles in internal tubular epithelia, such as the hindgut (M) and salivary glands (N). The arrow indicates Amph immunoreactive vesicles.