New pathways to neurogenesis: Insights from injury‐induced retinal regeneration

The vertebrate retina is a tractable system for studying control of cell neurogenesis and cell fate specification. During embryonic development, retinal neurogenesis is under strict temporal regulation, with cell types generated in fixed but overlapping temporal intervals. The temporal sequence and relative numbers of retinal cell types generated during development are robust and show minimal experience‐dependent variation. In many cold‐blooded vertebrates, acute retinal injury induces a different form of neurogenesis, where Müller glia reprogram into retinal progenitor‐like cells that selectively regenerate retinal neurons lost to injury. The extent to which the molecular mechanisms controlling developmental and injury‐induced neurogenesis resemble one another has long been unclear. However, a recent study in zebrafish has shed new light on this question, using single‐cell multiomic analysis to show that selective loss of different retinal cell types induces the formation of fate‐restricted Müller glia‐derived progenitors that differ both from one another and from progenitors in developing retina. Here, we discuss the broader implications of these findings, and their possible therapeutic relevance. Early‐ and late‐stage retinal progenitor cells (RPCs) can generate specific subtypes of retinal cells. In zebrafish retina, injury induces formation of Muller glia‐derived progenitor cells (MGPCs). MGPCs resemble late‐stage RPCs in their gene expression profile, but regenerate specific subtypes of both early and late‐born neurons that are selectively lost following injury.