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. Author manuscript; available in PMC: 2011 Nov 10.
Published in final edited form as: Annu Rev Cell Dev Biol. 2010 Nov 10;26:689–719. doi: 10.1146/annurev-cellbio-100109-104113

Figure 6.

Figure 6

A gradient of Frizzled (Fz) activity and cis-inhibition directs stochastic Notch signaling in the fly eye. (a) A gradient of Fz activity biases Notch activity such that R3 has high Notch activity and R4 has low Notch activity. As in the AC/VU example, feedback loops reinforce the fate decisions. (b) Development of the fly retina. A 5-cell precluster is determined followed by specification of R3 or R4 fate via Fz-directed Notch signaling. R1 and R6 are recruited to the cluster and then signal via Notch to induce R7 fate (completing photoreceptor recruitment). The clusters of cells rotate to their final position. (c) Cis-inhibition of Notch activity by Delta in R1/R6 cells induces directional Notch signaling to specify R7 fate. As in the AC/VU example, feedback loops reinforce the fate decisions. For simplicity, * indicates the Notch-mediated inputs via signaling from R6.