The emergence of neurogenic lineage motifs in building the vertebrate retina.

How does a single pool of progenitors generate the remarkable diversity of retinal neurons? This review synthesizes the molecular and lineage logic underlying this process. By integrating single-cell sequencing studies across multiple developmental stages, we first illustrate how retinal progenitor cells (RPCs), through stage-specific transcriptional and epigenetic states, produce major cell classes in a conserved temporal order, with a focus on human development. We then discuss the multilayer mechanisms regulating temporal competence transitions. Finally, we highlight the discovery of lineage motifs - reproducible neuronal outputs from neurogenic RPCs across species. These motifs reveal fundamental constraints on sibling fate coordination, canalize cell type variation during evolution, and serve as fundamental units for understanding cell type specification.