Repression of Nanog Gene Transcription by Tcf3 Limits Embryonic Stem Cell Self-Renewal

Abstract

The dual function of stem cells requires them not only to form new stem cells through self-renewal but also to form lineage-committed cells through differentiation. Embryonic stem cells (ESC), which are derived from the blastocyst inner cell mass, retain properties of self-renewal and the potential for lineage commitment. To balance self-renewal and differentiation, ESC must carefully control the levels of several transcription factors, including Nanog, Sox2, and Oct4. While molecular mechanisms promoting transcription of these genes have been described, mechanisms preventing excessive levels in self-renewing ESC remain unknown. By examining the function of the TCF family of transcription factors in ESC, we have found that Tcf3 is necessary to limit the steady-state levels of Nanog mRNA, protein, and promoter activity in self-renewing ESC. Chromatin immunoprecipitation and promoter reporter assays showed that Tcf3 bound to a promoter regulatory region of the Nanog gene and repressed its transcriptional activity in ESC through a Groucho interaction domain-dependent process. The absence of Tcf3 caused delayed differentiation of ESC in vitro as elevated Nanog levels persisted through 5 days of embryoid body formation. These new data support a model wherein Tcf3-mediated control of Nanog levels allows stem cells to balance the creation of lineage-committed and undifferentiated cells.

We would like to thank Randall Moon for his gift of the SuperTOPFlash and SuperFOPFlash plasmids, Ali H. Brivanlou for his gift of the Rex1-luciferase plasmid, Da Yong Wu for his gift of the Nanog promoter plasmid, and Jackson Hoffman for his helpful suggestions and critical reading of the manuscript.

This work was supported by funds awarded to B.J.M. from the American Cancer Society Illinois Division (grant no. 05-34), the Stem Cell Research Foundation, and the Schweppe Foundation.