Fig. 4

Optogenetic control of delta cell activity. Somatostatin reduces beta cell [Ca²⁺]_i oscillatory frequency and peak amplitude, and hyperglycemia is associated with impaired delta cell function and longer filopodia. a Photostimulation of delta cells expressing ChR2 evoked inward photocurrents under voltage clamp conditions (top; holding potential = −70 mV) and light-evoked, overshooting action potential-like responses under current-clamp conditions (bottom). Timing of light flashes (470 nm) is indicated by lower traces (L). Dashed line = 0 mV. b tdTomato and GCaMP6s/YFP fluorescence signal in wild-type and SST-ChR2 islets. c Top, protocol for in vivo imaging and ChR2-mediated photostimulation (450–470 nm light). Bottom, cartoon illustration representing the experimental setup and expected biological responses of GCaMP6⁺ beta cells and ChR2⁺ delta cells. d Representative beta cell [Ca²⁺]_i traces in islets from wild-type (top) or SST-ChR2 mice (bottom). e Normalized beta cell [Ca²⁺]_i peak amplitude and f peak frequency in wild-type (n = 7 islets) and SST-ChR2 islets (n = 5 islets) before and after ChR2 stimulation in vivo. e ***p < 0.001 by two-tailed student t-test and in f, ***p = 0.001 vs light-stimulated WT islets. In e, f data are displayed as fold change from nonstimulated conditions, represented by the horizontal pink dotted lines. Error bars represent the 95% confidence interval (C.I.) of the mean. For e, f source data are provided as a Source Data file