Differentiation of wing epidermal scale cells in a butterfly under the lateral inhibition model - Appearance of large cells in a polygonal pattern

Cellular pattern formations of some epithelia are believed to be governed b y the direct lateral inhibition rule of cell differentiation. That is, init ially equivalent cells are all competent to differentiate, but once a cell has differentiated, the cell inhibits its immediate neighbors from followin g this pathway. Such a differentiation repeats until all non-inhibited cell s have differentiated. The cellular polygonal patterns can be characterized by the numbers of undifferentiated cells and differentiated ones. When the differentiated cells become large in size, the polygonal pattern is deform ed since more cells are needed to enclose the large cell. An actual example of such a cellular pattern was examined. The pupal wing epidermis of a but terfly Pieris rapae shows a transition of the equivalent-size cell pattern to the pattern involving large cells. The process of the transition was ana lyzed by using the method of weighted Voronoi tessellation that is useful f or treatment of irregularly sized polygons. The analysis supported that the pattern transition of the early stage of the pupal wing epidermis is gover ned by the lateral inhibition rule. The differentiation takes place in orde r of largeness, but not smallness, of the apical polygonal area in the diff erentiating region of the pupal wing.