Copyright information:Taken from "An efficient system to establish multiple embryonic stem cell lines carrying an inducible expression unit"Nucleic Acids Research 2005;33(4):e43-e43.Published online 1 Mar 2005PMCID:PMC552969.© The Author 2005. Published by Oxford University Press. All rights reserved () Schematic representation of the induction of expression. The endogenous promoter was trapped by SA-tTA. In Tc− medium, tTA binds to the hCMV*-1 promoter, inducing expression of cDNA-IRES-Venus. () Induction of expression in EBRTcPGATA6 cells. mRNA and protein samples were prepared at 24 h after the induction. GAPDH and Oct-3/4 are used to normalize expression of Gata-6-specific mRNA and protein, respectively. It is known that endogenous Gata-6 protein is expressed at detectable level even in undifferentiated ES cells, and Oct-3/4 is expressed at the same level within 24 h after the induction of Gata-6 expression (). () Morphological changes in EBRTcPGATA6 cells during induction of Gata-6 expression. Cells were observed 24 (panels a and b), 48 (panels c and d), and 72 (panels e and f) h after induction of Gata-6 expression through a bright field (panels a, c, e and g) and through a YFP filter (panels b, d, f and h). In the non-induced cell population, stem cell colonies without fluorescence were observed after 72 h (panels g and h). () Expression induction in the cellular population. Open and striped boxes indicate undifferentiated and differentiated colonies, respectively. A marked increase in the number of differentiated colonies was observed 6 days after induction, whereas undifferentiated colonies were almost eliminated. Error bars represent mean ± 2 × SEM ( = 3).