A specific increase in inositol 1,4,5-trisphosphate 3-kinase B expression upon differentiation of human embryonic stem cells

Human embryonic stem cells (hESCs) are of great hope for regenerative medicine due to their dual pluripotency and self-renewal properties. We report a comparison of inositol phosphate (InsP s ) production in undifferentiated, differentiated hESCs and in two cancer cell lines, Ntera2 cells, a human embryonal carcinoma cell (hECC) line and HeLa cells. To evaluate the potential impact of InsP s in differentiation, hESCs were spontaneously differentiated in culture for two weeks. The distribution of the different InsP s was affected upon differentiation: the level of highly phosphorylated InsP s was decreased. In contrast, the total level of phosphoinositides (PI) was increased. Using real time quantitative PCR (qPCR), the mRNA expression of several enzymes of the metabolism of InsP s was determined: a specific increase in inositol 1,4,5-trisphosphate 3-kinase A and B (ITPKA and ITPKB) was observed upon hESCs spontaneous differentiation. Ins(1,4,5)P 3 3-kinase activity, undetectable in undifferentiated hESCs, increased upon differentiation. The same observation was made by Western blotting using an antibody directed against human ITPKB. This is the first report showing the potential implication of soluble InsP s in hESCs and possible function of isoenzymes of the inositol trisphosphate 3-kinase family in differentiation.