Cell cycle-dependent calcium oscillations in mouse embryonic stem cells.

Area of Science:

• Cell Biology
• Stem Cell Biology
• Calcium Signaling

Background:

• Somatic cells display distinct intracellular calcium (Ca2+) signaling patterns during cell cycle phases.
• Pluripotent embryonic stem cells (ESCs) lack G1 and G2 gap phases, prompting investigation into their Ca2+ signaling dynamics.
• Understanding Ca2+ signaling in ESCs is crucial for comprehending their unique cell cycle regulation.

Purpose of the Study:

• To investigate whether mouse embryonic stem (mES) cells exhibit characteristic intracellular Ca2+ concentration changes during cell cycle progression.
• To determine the mechanisms underlying Ca2+ oscillations in mES cells.
• To elucidate the role of Ca2+ signaling in mES cell cycle progression.

Main Methods:

• Confocal imaging using the Ca2+-sensitive dye fluo-4 AM to visualize intracellular Ca2+.
• Cell cycle synchronization techniques to isolate specific cell cycle phases.
• Pharmacological inhibitors and activators to probe Ca2+ signaling pathways, including inositol 1,4,5-trisphosphate (IP3) receptors and store-operated Ca2+ (SOC) channels.

Main Results:

• Undifferentiated mES cells exhibit spontaneous Ca2+ oscillations, primarily in the G1/S phase (approx. 70% of oscillating cells).
• These oscillations depend on IP3-mediated Ca2+ release and SOC influx, not Ca2+ influx.
• IP3-mediated Ca2+ release is essential for G1/S cell cycle progression, while SOC activation occurs in both G1/S and G2/M phases.

Conclusions:

• Ca2+ oscillations in mES cells are largely confined to the G1/S phase.
• IP3-mediated Ca2+ release is a critical regulator of mES cell cycle progression through G1/S.
• Altered IP3 receptor sensitivity or IP3 levels may underlie the G1/S-specific Ca2+ oscillations.