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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Eur Phys J E Soft Matter. 2010 Sep 23;33(2):129–148. doi: 10.1140/epje/i2010-10647-6

Figure 2.

Figure 2

(Color online) Some interactions involved in patterning R8 photoreceptors in the Drosophila eye. (A) Intercellular and intracellular regulation involved in fate specification in the epithelium of the eye imaginal disc. Only signals originating at the left cell and being received by the right cell are shown, but all interactions may be assumed to be reciprocal. Pointed arrows show a positive, activating influence; blunt arrows signify inhibition. The locations of gene names reflect the subcellular localization of the gene product. This diagram is necessarily incomplete, and most of the signals transmitted really on other genes during their production and transduction. N, Notch; Dl, Delta, Hh, Hedgehog; Sca, Scabrous; Ato, Atonal; and Sens, Senseless. (B) The simplified model studied in this paper. Diffusible activation is represented by h, with inhibitory activity lumped into u. The variable a takes the place of the proneural genes ato and sens. The multitude of different compartments present in a tissue are ignored, with each cell being treated as a lattice site, and intercellular signals moving on this lattice by diffusion (signified by the bi-directional arrows).