Visualizing Cell Cycle Phase Organization and Control During Neural Lineage Elaboration

In neural precursors, cell cycle regulators simultaneously control both progression through the cell cycle and the probability of a cell fate switch. Precursors act in lineages, where they transition through a series of cell types, each of which has a unique molecular identity and cellular behavior. Thus, investigating links between cell cycle and cell fate control requires simultaneous identification of precursor type and cell cycle phase, as well as an ability to read out additional regulatory factor expression or activity. We use a combined FUCCI-EdU labelling protocol to do this, and then apply it to the embryonic olfactory neural lineage, in which the spatial position of a cell correlates with its precursor identity. Using this integrated model, we find the CDKi p27(KIP1) has different regulation relative to cell cycle phase in neural stem cells versus intermediate precursors. In addition, Hes1, which is the principle transcriptional driver of neural stem cell self-renewal, surprisingly does not regulate p27(KIP1) in this cell type. Rather, Hes1 indirectly represses p27(KIP1) levels in the intermediate precursor cells downstream in the lineage. Overall, the experimental model described here enables investigation of cell cycle and cell fate control linkage from a single precursor through to a lineage systems level.