CAGE-seq of zebrafish cells extracted at the 14 somite stage and segregated by cell cycle dynamics (e.g. fast - green vs slow - red). CAGE-seq of zebrafish cells extracted at the 14 somite stage and segregated by cell cycle dynamics (e.g. fast - green vs slow - red)

The core-promoter, a stretch of DNA surrounding the transcription-start-site (TSS), is a major integration-point for regulatory-signals controlling gene-transcription. Cellular-differentiation is marked by divergence in transcriptional-repertoire and cell- cycling behaviour between cells of different fates. The role promoter-associated gene- regulatory-networks play in development-associated transitions in cell-cycle- dynamics is poorly understood. This study demonstrates in a vertebrate embryo, how core-promoter variations define transcriptional-output in cells transitioning from a proliferative to cell-lineage specifying phenotype. Assessment of cell-proliferation across zebrafish embryo-development, using the FUCCI-transgenic cell-cycle- phase marker, revealed a spatial and lineage-specific separation in cell-cycling behaviour. To investigate the role differential promoter-usage plays in this process, cap-analysis-of-gene-expression (CAGE) was performed on cells segregated by cycling-dynamics.