Notch-Delta signaling, salt-and-pepper patterning, fine-grained cell decisions
Lateral inhibition via Notch-Delta is a contact-mediated signaling mechanism that generates fine-grained, salt-and-pepper patterns of cell identities across a tissue. A cell with high Delta ligand activates Notch receptors on its neighbors, causing them to upregulate Hairy/Enhancer-of-split repressors that suppress Delta expression in those neighbors. This mutual antagonism forms a positive feedback loop: a slight stochastic advantage in Delta expression is amplified until the cell becomes a "sender" (Delta-high, Notch-low) surrounded by "receivers" (Notch-high, Delta-low). This mechanism selects sensory precursor cells in the Drosophila epidermis, specifies inner hair cells in the cochlea, and allocates intestinal secretory cells — always with a characteristic 1-in-N ratio determined by the inhibition range.