TCF3 and teratoma: We thank Wilfred F. van Ijcken and Wilfrid Richer for performing gene array analysis, Simona Rossi for performing miRNA array analysis, Wolter Oosterhuis for assistance with the teratoma analysis, Nina Solberg for kindly providing the Tcf3-promoter-constructs, Juanjiangmeng Du and Rosalie Joosten for technical assistance, and Frank van der Panne for assistance with figure preparation.