Directional cell rearrangement is a critical process underlying correct tissue deformation during morphogenesis. Although the involvement of F-actin regulation in cell rearrangement has been established, the role and regulation of actin binding proteins (ABPs) in this process are not well understood. In this study, we investigated the function of Coronin-1, a WD-repeat actin-binding protein, in controlling directional cell rearrangement in the Drosophila pupal wing. Transgenic flies expressing Coronin-1-EGFP were generated using CRISPR-Cas9. We observed that Coronin-1 localizes at the reconnecting junction during cell rearrangement, which is dependent on actin interacting protein 1 (AIP1) and cofilin, actin disassemblers and known regulators of wing cell rearrangement. Loss of Coronin-1 function reduces cell rearrangement directionality and hexagonal cell fraction. These results suggest that Coronin-1 promotes directional cell rearrangement via its interaction with AIP1 and cofilin, highlighting the role of ABPs in the complex process of morphogenesis.
Key words: Morphogenesis, Cell rearrangement, Actin binding proteins (ABPs)

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Calcium transients drive cells to discharge prostaglandin E₂ (PGE₂). We visualized PGE₂-induced protein kinase A (PKA) activation and quantitated PGE₂ secreted from a single cell by combining fluorescence microscopy and a simulation model. For this purpose, we first prepared PGE₂-producer cells that express either an optogenetic or a chemogenetic calcium channel stimulator: OptoSTIM1 or Gq-DREADD, respectively. Second, we prepared reporter cells expressing the Gs-coupled PGE₂ reporter EP2 and the PKA biosensor Booster-PKA, which is based on the principle of Förster resonance energy transfer. Upon the stimulation-induced triggering of calcium transients, a single producer cell discharges PGE₂ to stimulate PKA in the surrounding reporter cells. Due to the flow of the medium, the PKA-activated area exhibited a comet-like smear when HeLa cells were used. In contrast, radial PKA activation was observed when confluent MDCK cells were used, indicating that PGE₂ diffusion was restricted to the basolateral space. By fitting the radius of the PKA-activated area to a simulation model based on simple diffusion, we estimated that a single HeLa cell secretes 0.25 fmol PGE₂ upon a single calcium transient to activate PKA in more than 1000 neighboring cells. This model also predicts that the PGE₂ discharge rate is comparable to the diffusion rate. Thus, our method quantitatively envisions that a single calcium transient affects more than 1000 neighboring cells via PGE₂.

Keywords: prostaglandin E₂, imaging, intercellular communication, biosensor, quantification

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