During neurogenesis in the vertebrate retina, multipotent retinal progenitor cells (RPCs) exit the cell cycle and acquire postmitotic neuronal fates in a highly coordinated manner, but what triggers this transition? On p. 2107, Stephen Wilson and co-workers reveal that the local retinal environment plays a key role in this transition in zebrafish. In zebrafish, RPCs in a stem cell niche called the ciliary marginal zone (CMZ) differentiate into neurons throughout life. To study how these RPCs transition towards differentiation, the researchers used the zebrafish flotte lotte (flo) mutant. flo encodes Elys, a nuclear pore component required for cell-cycle progression. In flo mutants, the researchers report, CMZ cells retain the capacity to proliferate but do not enter their final neurogenic divisions to differentiate as neurons. However, in mosaic retinae, flo mutant cells near to wild-type retinal neurons progress from proliferation to differentiation. Thus, suggest the researchers, cell-extrinsic signals are able to over-ride a cell-cycle progression defect to promote differentiation of cell-cycle-defective neuronal progenitors.