Fig. 4.

Temporal patterning in mouse retinal progenitors. Retinal progenitor cells (RPCs) are converted from a neuroepithelium (NE) during embryonic stages. Together with genetic experiments, recapitulation of transcriptional trajectories by single-cell RNA-seq suggests that fetal RPCs transit throughout various competence windows that bias the production of various neuronal and glial fates. A series of tTFs (Ikfz1→Foxn4→Casz1→NFI) is emerging to drive progression throughout these competence windows. NFI coordinates the last glial fate with cell-cycle exit, thereby terminating the lineage. tTF progression is paralleled in RPCs with a gradient of microRNAs that terminate the early competence to generate ganglion cells by silencing Lin28b. It is unclear whether the microRNA gradient and the tTF series cross-regulate or constitute independent temporal systems. E, embryonic day; P, postnatal day.