During neurogenesis, lateral inhibition controls the final number of neurons. Neuronal precursors that express high levels of Delta prevent the neuronal differentiation of neighbouring cells by inducing Notch-dependent inhibitory signals in these neighbours. However, neurogenic wavefronts spread through non-neurogenic areas during development, so why isn’t lateral inhibition disrupted where these wavefronts contact non-neurogenic tissue? José María Frade, Saúl Ares and colleagues investigate this puzzle on . The researchers show that Delta-like 1 (Dll1) is widely expressed by non-neurogenic precursors at the periphery of the developing chick retina. Using a mathematical model of lateral inhibition, they show that the absence of Dll1 ahead of the neurogenic wavefront reduces the robustness of lateral inhibition, enhances neurogenesis and alters the shape of the neurogenic wavefront, predictions that are consistent with previous observations in the retina of mice in which Dll1 was conditionally mutated. The researchers propose, therefore, that Notch-independent Delta expression ahead of the neurogenic wavefront optimizes neurogenesis by preventing perturbations in lateral inhibition and wavefront progression.
