Insect epidermis: disturbance of supracellular tissue polarity does not prevent the expression of cell polarity

The insect integument displays planar tissue polarity in the uniform orientation of polarized cuticular structures. In a body segment, for example, the denticles and bristles produced by the constituent epidermal cells point posteriorly. Colchicine can abolish this uniform orientation while still allowing individual cells to form orientated cuticular structures and thereby to express cell polarity. This suggests that an individual cell in a sheet can establish planar polarity without reference to some kind of covert supracellular cue (such as a morphogen gradient) in the epidermis as a whole. The results also indicate that colchicine interferes - directly or indirectly - with the mechanisms involved in aligning the polarity axes of individual cells into a common orientation, thereby generating supracellular or tissue polarity.