T-type Ca2+ channels in mouse embryonic stem cells: modulation during cell cycle and contribution to self-renewal

Rodriguez-Gomez JA, Levitsky KL, Lepez-Barneo J. T-type Ca2+ channels in mouse embryonic stem cells: modulation during cell cycle and contribution to self-renewal. Am J Physiol Cell Physiol 302: C494-C504, 2012. First published November 2, 2011; doi: 10.1152/ajpcell. 00267.2011.-Ion channels participate in cell homeostasis and are involved in the regulation of proliferation and differentiation in several cell types; however, their presence and function in embryonic stem (ES) cells are poorly studied. We have investigated the existence of voltage-dependent inward currents in mouse ES cells and their ability to modulate proliferation and selfrenewal. Patch-clamped ES cells had inactivating tetrodotoxin (TTX)sensitive Na+ currents as well as transient Ca2+ currents abolished by the external application of Ni2+. Biophysical and pharmacological data indicated that the Ca2+ current is predominantly mediated by T-type (Ca(v)3.2) channels. The number of cells expressing T-type channels and Ca(v)3.2 mRNA levels increased at the G1/S transition of the cell cycle. TTX had no effect on ES cell proliferation. However, blockade of T-type Ca2+ currents with Ni2+ induced a decrease in proliferation and alkaline phosphatase positive colonies as well as reduced expression of Oct3/4 and Nanog, all indicative of loss in self-renewal capacity. Decreased alkaline phosphatase and Oct3/4 expression were also observed in cells subjected to small interfering RNA-induced knockdown for T-type (Ca(v)3.2) Ca2+ channels, thus partially recapitulating the pharmacological effects on self-renewal. These results indicate that Ca(v)3.2 channel expression in ES cells is modulated along the cell cycle being induced at late G1 phase. They also suggest that these channels are involved in the maintenance of the undifferentiated state of mouse ES cells. We propose that Ca2+ entry mediated by Ca(v)3.2 channels might be one of the intracellular signals that participate in the complex network responsible for ES cell self-renewal.