Figure 2. Temporal patterning of vertebrate neural progenitors.

(A) Temporal patterning in mouse retinal progenitors (RPCs). Five transcription factors temporally expressed in mouse RPCs have been shown to promote the production of different retinal cell types. In addition, scRNA-sequencing identified sets of genes differentially expressed in early vs. late RPCs that can be candidate temporal regulators. (B) Temporal patterning in mouse cortical progenitors (APs). Several transcription factors show temporal expression patterns in APs and regulate temporal specification of progeny fates. Foxg1 is required to repress layer I neuron generation, and promote deep layer neuron fates. In addition, Hmga2, Ikzf1, Foxp1 and Fezf2 were all shown to be required for deep layer neuron fates. COUP-TF I/II are required for the switch from generating deep layer neurons to generating superficial layer neurons. Furthermore, scRNA-sequencing identified groups of genes differentially expressed in early vs. late APs that can be candidate temporal regulators. (C) Temporal patterning in vertebrate spinal cord. Neurons born at different times express different transcription factors. A list of temporal genes were shown to be differentially expressed in early vs. late progenitors. Among them, Nfi factors were shown to be required for the generation of Neurod2 expressing neurons. The temporal transition in neural progenitors require TGF-β signaling.