Regulation of Ca²⁺ signaling during differentiation of embryonic stem cells into cardiomyocytes and neuronal cells

Proper intracellular Ca²⁺ signaling is essential for cell functions. However, the significance of intracellular calcium concentration ([Ca²⁺]_i) regulated by Ca²⁺ release from endoplasmic reticulum (ER) during early developmental stage of myocytes and neuronal cells have not yet been fully understood. It is believed that endoplasmic reticulum (ER)-function is rudimentary in the fetal heart and embryonic stem cell (ESC) derived cardiomyocytes (ESCMs). Also it remains unclear whether intracellular Ca²⁺ mobilization from type 2 ryanodine receptor (RyR2) is required in the activity-dependent neurogenesis. Using murine ESCs as an in vitro model of cardiomyogenesis and neurogenesis, we demonstrate that functional RyR2 are essential to the rapid upstroke and frequency of Ca²⁺ transients, which regulate contractions with the differentiation of ESCMs; and neurogenesis induced by activation of GABA_A receptors and L-type Ca²⁺ channels depends critically on the functional RyR2. These results reveal that ESCMs have the potential to form a functional ER that is necessary for eventual therapeutic viability. An intimate cooperation of L-type Ca²⁺ channels with RyR2 is crucial for the activity-dependent neurogenesis induced by paracrine and/or autocrine GABA signaling.