Quiescence (reversible cell-cycle arrest) and senescence (irreversible arrest) are challenging to distinguish due to a lack of specific biomarkers, yet both arise simultaneously after chemotherapy. While senescence suppresses tumors by limiting proliferation and recruiting the immune system, quiescent cancer cells evade future therapies and may resume proliferation. Here, we pair time-lapse imaging of cell-cycle dynamics with single-cell RNA sequencing after etoposide treatment to differentiate these states, linking heterogeneous cell-cycle phenotypes to the transcriptomic landscape. We identify diverse senescent types (senotypes) and link them to two arrest pathways — a gradual path arising after a standard mitosis-to-G0 transition, and an alternative direct path driven by a mitotic slip. Using pseudotime trajectory analysis, we find that senescent phenotypes begin to manifest early and gradually along the first trajectory, even in shallow quiescent cells. These data support a model wherein, following chemotherapy, quiescence and senescence exist on a continuum of cell-cycle withdrawal at a transcriptome-wide level. Quiescent and senescent cells often arise side by side after stress, yet their molecular relationship remains unclear. Here, the authors combine live-cell imaging and single-cell RNA sequencing to reveal a continuum of cell-cycle withdrawal.

The Nobel laureate and CU Boulder professor, recently ranked #1 globally for RNA research, will speak at the World Economic Forum annual meeting in Davos,

The subcellular localization of many mRNAs to neuronal projections allows neurons to efficiently and rapidly react to spatially restricted external cues. However, for most of these RNAs, the mechanism...