Figure 1: GNEO approach and epithelial comparisons performed.

(a) GNEO approach to characterise epithelial organisation. (1) Images from the confocal microscope are processed to get a light background with dark cell contours. (2) The processed image is the source for defining individual cells, as well as for determining the number of neighbours for every cell. (3) This information is used to produce an epithelial network where each cell is represented as a node, and the two nodes are connected if the two cells are neighbours in the epithelium. (4) A region of interest (ROI; shown in a green box) is selected for further analysis and the cells that border the ROI are excluded. (5) The average and s.d. of area and three network features over all cells in an epithelium are calculated. (6) This information is represented as a feature vector, which is an eight-dimensional vector that characterises each epithelium. Each of the four features considered in this work is abbreviated by the symbols shown in this figure. (b) Schematic representation of the comparisons of epithelia from different sources performed in this study. Images of representative epithelial samples (2-pixel wide cell contour) from Drosophila (different tones of green labels, fly) and chick (different tones of brown labels) are shown. The reference prepupal wing pouch epithelium is shown within a grey box. The text in grey denotes the relationship between epithelia from the different sources that were compared. Space: spatially separated epithelia from the same organism; time: temporally separated epithelia from different stages of development; type: different types of epithelia (that is, squamous and columnar); species: epithelia from different organisms (vertebrate (chick) and invertebrate (Drosophila)) and mutation: mutant epithelia.