Epithelial cells adhere to the extracellular matrix (ECM) below through integrins on their basal surface. In some cases, such as the mammalian inner ear and developing fly wing, they also interact with an apical ECM (aECM) above; however, these interactions are less well understood. On , Nicholas Brown and co-workers describe two fly proteins - Piopio and Papillote - that appear to play important roles in aECM interactions. The authors show that these proteins localize to the apical surface of the pupal wing epithelium. Moreover, they find that mutations in the corresponding genes lead to wing blistering and detachment of the epithelium from the aECM above. Whereas Papillote is evenly distributed at the apical surface, Piopio has a punctate distribution. In addition, Brown and co-workers note that loss of Piopio but not Papillote disrupts the specialized microtubule bundles that link apical and basal junctions in these cells. They therefore conclude that the two proteins are involved in organization of the aECM but Piopio has additional roles in microtubule assembly. Since Piopio and Papillote share zona pellucida (ZP) domains with tectorin proteins in the inner ear, related proteins might play similar roles in mammals.
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