Spontaneous [Ca2+]i oscillations in G1/S phase-synchronized cells

Ca(2+) signaling controls a wide range of cellular functions such as division, fertilization, apoptosis and necrosis. Specifically, calcium signaling is thought to play a crucial role in driving cells through the different stages of the cell-division cycle. In most cells, however, this fact is far from being established. Few studies have examined this question from a different perspective: whether cells exhibit some characteristic cell cycle-dependent intracellular calcium-signaling patterns. This approach is effective in discerning the causal relationship between Ca(2+) signaling and the cell cycle. Through synchronization of the cell cycle, flow cytometry and confocal scanning microscopic intracellular calcium ion concentration ([Ca(2+)](i)) imaging, the present study shows that the G1/S phase transition is uniquely characterized by spontaneous [Ca(2+)](i) oscillations that last for up to 40 min. Most likely, these oscillations emanate from the [Ca(2+)](i) signaling that accompanies DNA replication as the cell prepares for the next division cycle. These temporal signals further affirm the significance of Ca(2+) in the cell cycle.