Hes proteins are transcription factors that are dynamically expressed during embryonic development, and are important for proper somitogenesis and neural development. However, it remains unclear how the oscillations in Hes expression differ across cell types during vertebrate development. Here, Ina Sonnen and colleagues study the dynamics of Hes1 across various tissues in the mouse embryonic tail. First, the authors generate an endogenously tagged, homozygous viable, Hes1-Achilles mouse reporter line. This reporter line is used to quantify Hes1 dynamics in different adjacent regions of the tail – the tailbud, the pre-neural tube and the presomitic mesoderm (PSM). Analysing at both the population and single-cell level in Hes1-Achilles tail explants, the authors find that, in pre-neural tube cells, Hes1 oscillates at high expression level but lacks population-wide synchronization. In contrast, in PSM cells, Hes1 oscillations are at lower levels but highly synchronized. In addition, the authors investigate the role of Notch signalling in driving Hes1 oscillations. They observe that the PSM and the developing neural tube respond to pharmacological inhibition of Notch signalling differentially, suggesting the mechanisms driving Hes1 oscillations differ between the two cell types. Overall, the findings show that Notch-driven Hes1 oscillation dynamics are cell-type specific in the developing mouse tail.
