Joint recording of past and present transcriptomes reconstructs single-cell trajectories

Tracing molecular cell state transitions through development, homeostasis and disease is still beyond reach at single-cell resolution. We present scReMeMber-Seq, a methylation-based cell-memory recorder connecting past transcriptional states with present transcriptome and DNA methylome in individual cells. scReMeMber-Seq leverages pulse induction of DCM-Polr2b (TimeMachine) and single-cell methylome-transcriptome (scMT) sequencing for endpoint readout. In mouse neural stem cells (NSCs) and pancreatic organoids, single-cell DCM methylation profiles (scDCMome) accurately discriminate cell types. Over time, scDCMome also record NSC quiescence-activation state changes across multiple cell divisions. In zebrafish embryos, scDCMome resolve individual transcriptional trajectories from progenitor to neuron. Together, scReMeMber-Seq enables real time reconstruction of cellular trajectories, connecting past and present molecular states in single cells, at genome scale, across experimental systems, in vitro and in vivo .