Figure 1.
Functional Mapping of β Cell Population Dynamics
(A) At elevated glucose (11 mM), islets house a scale-free network where a few (<10%) β cells host the majority of correlated links (p < 0.01), as shown by the power law-fitted probability distribution (LC, low connectivity range; HC, high connectivity range) (R2 = 0.72) (n = 12 recordings from five animals). A log-log scale is used to convert the power law into a linear relationship.
(B) Representative functional connectivity map displaying the x-y position of analyzed cells and their links (followers, blue; hubs, red; scale bar, 20 μm).
(C) Representative trace showing that hub (red) activity tends to precede and outlast that of follower cells (gray) (mean lag value calculated from n = 5 recordings from three animals).
(D) Treatment of islets with the gap junction blocker 18α-glycyrrhetinic acid (AGA; 20 μM) (left), but not its inactive analog glycyrrhizic acid (BGA; 20 μM) (right) reduces the proportion of hubs (n = 9 recordings from five animals) (before, islet in control buffer; after, same islet in the presence of either AGA or BGA).
(E) As for (D), but the proportion (%) of correlated links.
(F and G) Gap junction blockade increases the length between correlated links (n = 9 recordings from five animals).
(H) Wiring patterns are statistically stable upon re-recording after 30 min, as determined against the same islet but with enforced dissimilarity (n = 8 recordings from five animals).
(I) Wiring patterns are statistically stable upon re-recording after 30 min (Fluo2) and 3 hr (GCaMP6), as compared to the randomly shuffled correlation matrix for each islet (n = 4–6 recordings from two to three animals).
(J) As for (A) but showing almost identical link-probability distributions in mouse and human islets, as shown by the exponent values (κ) for the fitted power laws (n = 8 recordings from three donors).
(K and L) Imaging using GCaMP6 and Fluo2 return similar hub and link proportions (n = 12 recordings from four to six animals).
Data are means ± SEM.∗p < 0.05 and ∗∗p < 0.01. NS, non-significant. See also Figure S1 and Movie S1.