Independent Component Analysis of Intracellular Calcium Spike Data

Calcium (Ca2+)is an ubiquitous intracellular messenger which regulates cellular processes, such as secretion, contraction, and cell proliferation. A number of different cell types respond to hormonal stimuli with periodic oscillations of the intracellular free calcium concentration ([Ca2+]i). These Ca2+ signals are often organized in complex temporal and spatial patterns even under conditions of sustained stimulation. Here we study the spatio-temporal aspects of intracellular calcium ([Ca2+]i) oscillations in clonal J3-cells (hamster insulin secreting cells, HIT) under pharmacological stimulation (Schofi et al., 1996). We use a novel fast fixed-point algorithm (Hyvarinen and Oja, 1997) for Independent Component Analysis (ICA) to blind source separation of the spatio-temporal dynamics of [Ca2+]i in a HIT-cell. Using this approach we find two significant independent components out of five differently mixed input signals: one [Ca2+]i signal with a mean oscillatory period of 68s and a high frequency signal with a broadband power spectrum with considerable spectral density. This results is in good agreement with a study on high-frequency [Ca2+]j oscillations (Palus et al., 1998) Further theoretical and experimental studies have to be performed to resolve the question on the functional impact of intracellular signaling of these independent [Ca2+]i signals.