Bidirectional folding of an insect epithelial monolayer

Moth wing epithelium has a well‐defined apicobasal polarity expressed in the positioning of specialized junctions and microfilament bundles. This cytoarchitecture predisposes epithelial monolayers to fold with their basal surfaces outermost. However, a given epithelial population appears not to be constrained by its cytoarchitecture to fold in a particular direction. Direction of folding—either with basal surfaces or apical surfaces outermost—is determined by environmental factors and is correlated with changes in lateral cell contacts as well as dimensions of the apicalmost epithelial junctions (belt desmosomes). These configurational changes of epithelial sheets are accomplished without altering the intrinsic polarity of individual epithelial cells.