Fig. 1
Patch clamp recordings of Na+ currents from hESC-derived RPE. a, b Brightfield light microscopy images of hESC-derived RPE cells. a Mature hESC-derived RPE grown on insert for 2 months showing strongly pigmented cells and characteristic epithelial morphology. b Mature hESC-derived RPE was dissociated yielding single cells with typical morphology showing pigmented apical and non-pigmented basal sides. Scale bars 10 μm. Whole-cell patch clamp recordings as responses to a series of depolarizing voltage pulses (− 80 to + 60 mV, 10 mV steps) after strong hyperpolarization (− 170 mV) either c from mature monolayer of hESC-derived RPE or d from single hESC-derived RPE cells. Patch clamp pipette is visible in the center of the a and b images. e–i Analysis of the monolayer recordings. e The average current–voltage relationship (I vs Vm, mean ± SEM, n = 12). f Steady-state inactivation curve was analyzed by plotting the normalized peak current at − 10 mV test pulse against the prepulse voltage (− 140 to − 40 mV, 10 mV steps) and fitting the data with the Boltzmann equation. The best fit was obtained with V1/2 = − 94 ± 1 mV and k = 10 (n = 7). Data points indicate mean ± SEM. g, h The time dependency of recovery from inactivation. The second peak currents were normalized and plotted against the voltage pulse interval (10–270 ms). The best fit to an exponential function was obtained with τ = 54 ± 3 ms (n = 5) (individual datapoints for h available in Additional file 7: Table S2). i The activation (squares) and inactivation (circles) time constants were obtained from single exponential fits to the rising and decaying phases of the current responses shown in c and plotted against the command voltage (n = 7). j Summary of the patch clamp results