A realistic model of fluorescence fluctuations in intracellular calcium images

ESTEFANÍA PIEGARI, LUCÍA LOPEZ, EMILIANO PEREZ IPIÑA, SILVINA PONCE DAWSON

Otro; XV Giambiagi Winter School; 2013

Calcium signaling is ubiquitous across cell types. Intracellular calcium signals are observed in intact cells with minimum disruption using calcium dyes. The observations, however, are indirect since they report on the Ca2+-bound dye rather than the free Ca2+ distribution. Given an image, it is important to know to what extent it is affected by the dye properties and whether it provides an accurate representation of the underlying Ca2+ spatio-temporal dynamics. To this end, having a working mathematical model that allows a direct comparison with experimental observations is desirable. Fluorescent images are noisy. A more quantitative comparison between experiments and model then requires that fluctuations be included in the latter. In this work we present a realistic model of fluorescence fluctuations that, in combination with a mathematical model of the cytosolic calcium dynamics, can be used to generate numerically simulated noisy images of calcium signals. The model is based on the one that underlies the Number and Brightness technique but it is extended so as to take into account that calcium dyes can fluoresce with or without calcium bound, albeit with different intensity. By means of a detailed analysis of the fluorescence fluctuations observed in Xenopus Laevis oocytes under basal conditions we are able to derive the main model parameters. We describe the main model properties and show its ability to generate noisy calcium signal images that can readily be compared with experimental ones.