Figure 2. Transcription programs in stem cells.

Figure 2Transcription programs in stem cells.

Transcription factors control the molecular circuits that govern stem cell identity. A. In ESCs, key pluripotency-associated factors Oct4, Sox2, Nanog and Sall4 form auto-regulatory loops that maintain their own transcriptional activity and gene expression. The stability of this set of core factors is further enhanced through the interconnectivity of these loops. B. During myogenesis, MyoD is an upstream regulator which activates the expression of MyoG. Both TFs are necessary for the myogenic program, and regulate a common subset of genes in a temporal manner. MyoD must initiate chromatin remodeling of genes for these to be subsequently bound and regulated by MyoG. C. The same TF, Sall4, have dual roles in controlling discrete circuits in the different embryo-derived stem cell lines, ESCs and XEN cells. In the respective cell types, Sall4 regulates distinctive sets of key factors that contribute to the specific cellular identity. In ESCs, Sall4 activates Oct4, Sox2 and Nanog; all of which positively feedback onto the Sall4 promoter. In XEN cells, Sall4 activates Gata4, Gata6, Sox7 and Sox17 which are necessary for the undifferentiated state. Whether these regulated factors directly feedback onto the Sall4 promoter is not known.

From: Genome-wide transcription factor localization and function in stem cells

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StemBook [Internet].
Cambridge (MA): Harvard Stem Cell Institute; 2008-.
Copyright: © 2008 Wai-Leong Tam and Bing Lim.

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