Fig. 4: Calcium transient activity was increased and more synchronized in hippocampal neurons harboring PINK1 and PRKN mutations compared to healthy controls.

a A sample video frame of a calcium imaging recording. Red marks represent neurons marked as the region of interest. b The corresponding fluorescence time series plot for all marked neurons in a. An example heatmap of the mean correlation value of area recorded area from (c) control hippocampal DG granule neuron network and (d) hippocampal DG granule neuron network with PINK1 and PRKN mutation. e The average correlation in the top correlated areas (see Methods) of hippocampal DG granule neuron cultures with PINK1 and PRKN mutations was larger compared to control neuronal culture. Representative areas of (f) control hippocampal DG granule neurons culture and (g) hippocampal DG granule neurons culture with PINK1 and PRKN mutation with high synchronous activity. The PINK1 and PRKN mutant neuronal cultures exhibited high synchrony. Representative calcium transient time series plot with a high event frequency of (h) a control hippocampal DG granule neuron and (i) a hippocampal DG granule neuron with PINK1 and PRKN mutation. The PINK1 and PRKN mutant neuronal cultures exhibited high-frequency firing patterns. j The top 5 ratio of area under the power spectral density curve of such fluorescent signals between the whole frequency spectrum and higher frequency components was larger in PINK1 and PRKN mutant neurons compared to controls. k–n A representative plot of fluorescence transients at the first time point (k) in control neurons and (l) in PINK1 and PRKN mutant neurons. Examples for the second time point are shown in (m) for controls and (n) for PINK1 and PRKN mutant neurons. The second time point. Increased activity can be observed in the mutant neurons, and higher synchrony can be observed in the mutant neurons in the second time point. At the first time point of calcium imaging (o), the average astrocytes fluorescence ratio Δf/fo (see Methods) was significantly decreased in hippocampal PINK1 and PRKN mutant neurons, whereas (p) the calcium fast transients’ event (attributed to the neurons) rate was increased in hippocampal PINK1 and PRKN mutant neurons. At the second time point of calcium imaging (q), the average astrocytes fluorescence ratio Δf/fo was significantly lower in hippocampal PINK1 and PRKN mutant neurons, and (r) the calcium fast transient event rate (attributed to the neurons) was higher in neurons of hippocampal PINK1 and PRKN mutant neurons. Asterisks in this figure denote statistical significance as indicated by the following codes: *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.