Cell-cell communication correlates with pattern formation in molting Manduca midgut epithelium.

The midgut epithelium of larval Manduca sexta is constructed of single goblet cells surrounded by a one-cell-thick reticulum of columnar cells. This pattern is expanded at each molt by the addition of new cells. Between molts, these epithelial cells are not dye coupled, even though gap junctions are present. Proliferating stem cells are dye coupled in small groups early in the molt. Then, at mid-molt, the whole epithelium temporarily becomes dye coupled. This is when the new (expanded) pattern is being established. Later, at the end of the molt, the epithelium returns to the non-coupled state. These results suggest that cell communication via gap junctions may play a role in cell patterning.