Early cAMP signaling orchestrates single-cell synchronicity throughout Dictyostelium development.

Synchronicity is observed in many biological systems, including development, as seen in vertebrate body axis formation, fly eye development, and development of the social amoeba D. discoideum. Despite its prevalence, quantitative analyses of synchronicity at the single-cell level remain rare. Here we show that synchronicity in D. discoideum is mediated by early cAMP signaling. Using single-cell RNA sequencing (scRNA-seq), we quantify transcriptome similarities between individual cells during development. We show that synchronicity first declines upon starvation but then increases with the onset of cAMP-pulse signaling. Synchronicity remains stable throughout development and differs between prespore and prestalk cells. Genetic perturbations of cAMP production and response reveal that cAMP signaling is essential for establishing and maintaining synchronicity, as its absence leads to highly asynchronous development. These findings highlight the role of cAMP signaling in coordinating transcriptomic and morphological synchronicity, and establish scRNA-seq as a tool for quantitative analysis of developmental synchronicity.