Figure 5.

Cell state space discretization and time-dependence of models of pancreatic β-cell maturation and proliferation. (a) Concept of state- and time-dependent effects in vivo. Cell state-dependent effects (cell color) directly depend only on the molecular state of the cell. Time-dependent effects (background color) are invariant with respect to the cell state. Time-dependent effects depend directly only on extracellular regulators if the cell state variable captures the full molecular state of a cell. (b) Surface marker-based compartment model for β-cell maturation. Here, the presence of Ucn3 is used as a marker for maturation within the set of Ins⁺ cells. (c) Continuous trajectory model of β-celll maturation in cell state space. Here, pseudotime quantifies maturation as cell state in a continuous interpolation of the two states shown in (b). The boxplots show the distribution of single-cell RNA-seq samples across cell state space by sampled time point with n_x cells per time point x: n₀=61, n_1.5=84, n_4.5=88, n_10.5=81, n_16.5=59, n_19.5=71, n_61.5=131. The center of each boxplots is the sample median, the whiskers extend from the upper (lower) hinge to the largest (smallest) data point no further than 1.5 times the interquantile range from the upper (lower) hinge. (d) Maturation quantification of β-cells in pancreas sections via co-staining of DAPI, insulin (β-cells) and Ucn3 (β-cell maturation) at multiple time points (P0, P4, P9, P14). The fractions of cells in the two compartments shown in (b) can be directly counted in these sections. We quantified the proliferation of 1000–3300 β-cells in 3 animals per animal per time point. White scale bar: 50 μm.