Figure 4. Hypothetical signaling schemes for regulating cellular pattern formation in the growing fish retina

Top: Differentiated inner retinal cells of a particular type ("cyan") inhibit the differentiation of like-type cells via a signaling mechanism that is modeled as a decaying exponential (arbitrary ordinate scale). Unlike cell types are not directly affected. Ongoing modeling work has suggested that this relatively simple signaling scheme provides good estimates of the observed patterns for several distinct inner retinal cell types (unpublished data and [70]), and thus may represent a general mechanism for the regulation of cellular patterns in the inner retina. Bottom: At the level of cone photoreceptors, ongoing modeling work (Cameron and Carney, in preparation) suggests that signaling mechanisms that affect both like- and unlike-cell types are required for the establishment of square-shaped cone patterns similar to those illustrated in Figure 1 above. In the illustrated case, the "red" cones inhibit their own differentiation, but promote the differentiation of the "blue" cone type; the "blue" cones exert the opposite influence.