Abstract
Ultradian oscillations of HES Transcription Factors (TFs) at the single‐cell level enable cell state transitions. However, the tissue‐level organisation of HES5 dynamics in neurogenesis is unknown. Here, we analyse the expression of HES5 ex vivo in the developing mouse ventral spinal cord and identify microclusters of 4–6 cells with positively correlated HES5 level and ultradian dynamics. These microclusters are spatially periodic along the dorsoventral axis and temporally dynamic, alternating between high and low expression with a supra‐ultradian persistence time. We show that Notch signalling is required for temporal dynamics but not the spatial periodicity of HES5. Few Neurogenin 2 cells are observed per cluster, irrespective of high or low state, suggesting that the microcluster organisation of HES5 enables the stable selection of differentiating cells. Computational modelling predicts that different cell coupling strengths underlie the HES5 spatial patterns and rate of differentiation, which is consistent with comparison between the motoneuron and interneuron progenitor domains. Our work shows a previously unrecognised spatiotemporal organisation of neurogenesis, emergent at the tissue level from the synthesis of single‐cell dynamics.
Highlights
Neurogenesis is the developmental process which generates the variety of neuronal cell types that mediate the function of the nervous system
The differences in Venus::HES5 intensities were displayed using the “viridis” (Venus)::HES5 intensity between nuclei did not correlate with the Draq5 nuclear staining indicating this was not related to global effects or effects of imaging through tissue (Fig EV1C)
We have investigated the fine-grained pattern of neurogenesis in the spinal cord by monitoring the spatiotemporal patterning of key progenitor Transcription Factors (TFs) HES5 using live imaging analysis that is optimised towards revealing coordinated tissue-level behaviour that would not otherwise be evident
Summary
Neurogenesis is the developmental process which generates the variety of neuronal cell types that mediate the function of the nervous system. Recent live imaging studies of cell fate decisions during neurogenesis have added a new dimension to this knowledge (Vilas-Boas et al, 2011; Das & Storey, 2012, 2014; Manning et al, 2019; Nelson et al, 2020; Soto et al, 2020). They have shown the importance of understanding transcription factor (TF) expression dynamics in real time, including the key transcriptional basic helix–loop–helix repressors Hairy and enhancer of split (HES) and 5 (Ohtsuka et al, 1999; Imayoshi & Kageyama, 2014; Bansod et al, 2017), in regulating state transitions. Our studies of a zebrafish paralogue Her showed that the transition from aperiodic to oscillatory expression is needed for neuronal differentiation, suggesting that oscillatory expression has an enabling role for cell state
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