Distinct neurogenic progenitor cell populations balance cell type production in the embryonic mouse retina

Mammalian vision relies on the precise production of over 100 distinct neural cell types by multipotent retinal progenitor cells. The manner in which these cell types are generated in the correct proportions across the retina has remained unclear. By focusing on the early embryonic stage in mice, researchers discovered that retinal neurogenesis is organized through distinct populations of neurogenic progenitor cells (NPCs) with specific biases towards producing particular cell types.

NPCs that express Galanin primarily generate retinal ganglion cells and amacrine cells, while those expressing Olig2 produce cones and horizontal cells. Through clonal analysis, the team found that these two populations of NPCs with distinct fates emerge mainly from asymmetric divisions that yield one daughter cell with a predetermined fate.

The production of these NPCs is regulated by differential Notch signaling, with NPCs expressing Galanin being in a NotchHigh state and those with Olig2 being in a NotchLow state. By manipulating Notch signaling, the researchers were able to alter the production of these NPC populations. Moreover, the expression of Notch signaling components among NPCs suggests a mechanism of lateral inhibition, where fate-biased NPCs promote neighboring cells to adopt a complementary fate-biased state.

These findings imply that the consistent and diverse production of retinal cell types is achieved through a local feedback mechanism that balances discrete, fate-biased populations of NPCs.