Fig 1. Identification of first responder cells.

(A) Schematic of where data was collected. (B) Representative image of 2D islet plane with false-color map of response time to glucose elevation. (C) Representative distribution of response time, Tresp, for the cells shown in (B). Pie chart describes definition of 1st (last) responder cells as 10% of all cells in the islet 2D plane that have fastest (slowest) Tresp. See source data. (D) Representative time course of [Ca²⁺] dynamics within an islet shown in (B) following glucose elevation from 2 to 11 mM. In red rectangle: first phase of the [Ca²⁺] response, in blue–second phase. Red curves correspond to first responder (1st-resp) cells and green–to last responder (last-resp) cells. (E) Link map based on the functional network analysis performed over the second-phase dynamics in the islet shown in (B and E). Hub-like (ph2) cells are shown as blue dots. (F) Phase1 [Ca²⁺] dynamics metric: response time following glucose elevation. Comparison of β-cells leading phase1 (1st responder ph1) vs. phase2 (leader ph2), vs. hub-like (ph2) cells collected from 271 cells, 8–12 islets, 6–7 mice. (G) Phase2 [Ca²⁺] dynamics metric: lag of the cell’s [Ca²⁺] wave with respect to the islet-average wave. Comparison of β-cells leading phase1 vs. phase2 vs. hub-like (ph2) cells (n = 4–12 islets from 4–7 mice). (H) Percent of functional links normalized to max number of links, identified during second phase of [Ca²⁺] dynamics (n = 8 islets from 6 mice). (I) Example of measurement of the distance from one of the 5 first responder cells in this islet to other cells. (J) Quantification for multiple islets (n = 8 islets from 6 mice), where each dot represents average distance from all first responder cells to other cell states per islet. Statistical analysis in F, G utilized linear mixed effect model fit by REML with islet and mouse as a random effect (S2 Statistical analysis LMEM), H, J: utilized 1-way ANOVA (with Dunnett’s multiple comparison test), where **** represents p < 0.0001, *** p < 0.0002, ** p < 0.0021, * p < 0.0332 for comparison of the islet-average value vs. all other groups. Functional network analysis was performed via binarization and co-activity matrix analysis, as described [20]. See S1 Data file for values used in each graph. LMEM, linear mixed-effects model.