Live imaging of individual cell divisions in mouse neuroepithelium shows asymmetry in cilium formation and Sonic hedgehog response

Here we integrate several fluorescent markers and use ex vivo live imaging of a single cell division within the mouse E8.5 neuroepithelium to reveal both the formation of a primary cilium and the transcriptional response to Sonic hedgehog in the daughter cells.We show that, upon cell division, cilia formation and the Sonic hedgehog response are asynchronous between the daughter cells.Our results demonstrate that we can directly observe single cell divisions within the developing neuroepithelium and concomitantly monitor cilium formation or Sonic hedgehog response. We expect this method to be especially powerful in examining whether cellular behavior can lead to both differentiation and maintenance of cells in a progenitor niche.Primary cilia are critical for a number of signaling pathways linked to cell proliferation and differentiation [1-3]. They are often thought of as cellular antennae because they send and receive signals [4-6]. In dividing cells, the cilium must be generated anew after each cell division. The cilium projects from the older centriole of the centrosome, so generation of the cilium is tightly linked to centriole duplication and to the cell cycle [7]. Recent work demonstrated that, in cell culture, the daughter cell that inherits the older mother centriole generates a primary cilium and responds to external stimuli before its sister cell [8]. This asynchrony implies that cell fate may be controlled, in part, by the timing of cilia formation.The timing of cilia formation could be especially critical during development as cell divisions are required for both differentiation and maintenance of progenitor cell niches. Most often these distinct fates are physically juxtaposed, raising the question of how cells under such similar environmental cues manage such different responses. Asynchrony in cilium formation offers a potential mechanism. Under such a scenario, when a progenitor divides, one daughter cell forms a cilium and responds to signaling quick