Small Increases in the Level of Sox2 Trigger the Differentiation of Mouse Embryonic Stem Cells

Abstract

Previous studies have demonstrated that the transcription factor Sox2 is essential during the early stages of development. Furthermore, decreasing the expression of Sox2 severely interferes with the self-renewal and pluripotency of embryonic stem (ES) cells. Other studies have shown that Sox2, in conjunction with the transcription factor Oct-3/4, stimulates its own transcription as well as the expression of a growing list of genes (Sox2:Oct-3/4 target genes) that require the cooperative action of Sox2 and Oct-3/4. Remarkably, recent studies have shown that overexpression of Sox2 decreases expression of its own gene, as well as four other Sox2:Oct-3/4 target genes (Oct-3/4, Nanog, Fgf-4, and Utf1). This finding led to the prediction that overexpression of Sox2 in ES cells would trigger their differentiation. In the current study, we initially engineered mouse ES cells for inducible overexpression of Sox2. Using this model system, we demonstrate that small increases (twofold or less) in Sox2 protein trigger the differentiation of ES cells into cells that exhibit markers for a wide range of differentiated cell types, including neuroectoderm, mesoderm, and trophectoderm but not endoderm. We also demonstrate that elevating the levels of Sox2 quickly downregulates several developmentally regulated genes, including Nanog, and a newly identified Sox2:Oct-3/4 target gene, Lefty1. Together, these data argue that the self-renewal of ES cells requires that Sox2 levels be maintained within narrow limits. Thus, Sox2 appears to function as a molecular rheostat that controls the expression of a critical set of embryonic genes, as well as the self-renewal and differentiation of ES cells. STEM CELLS 2008;26:903-911 Disclosure of potential conflicts of interest is found at the end of this article.

Ube2s regulates Sox2 stability and mouse ES cell maintenance

“…47 Of note, the role of Sox2 is highly dosagedependent. 4,44 In ES cells, both elevation and depletion of Sox2 results in cell differentiation. [3][4][5] Hence, controlled regulation of Sox2 expression to fine-tune its level becomes critical for the maintenance of ES cells and cell lineage commitment.…”

“…Both its elevation and depletion can trigger ES cell differentiation. [3][4][5] It is of great interest to dissect the mechanisms controlling the precise level of Sox2 in ES cells. Although extensive studies have uncovered how Sox2 is transcriptionally activated or repressed, 2,6 posttranslational regulation of Sox2, in general, and its degradation, in particular, remains to be elucidated.…”

Completion of a programmable DNA-binding small molecule library

“…35,36 Aminolysis furnishes the polyamide, which can be further derivatized on the turn or tail residues. The selection of either β-Ala-PAM or Kaiser oxime resin yields different C-terminal groups following cleavage with a primary 6).…”

“…In the hairpin binding motif, β-alanine has been found to be a good structural replacement for Py, as the β/Im pair is specifi c for C•G and β/Py and β/β both code for A,T. 36,37 Furthermore, when β replaces Py adjacent to Im, binding is generally improved, as this fl exible residue is believed to allow the amino acid pairings to reset their register with the DNA base pairs. 37,38 A key example of the use of β to replace Py can be seen in polyamide 26.…”

“…An additional experiment with R1 mouse ES cells was designed to increase the incubation period to 72 hours, allowing more time for potential phenotypic changes. 36 Instead of harvesting after 72 hours, the medium was changed and compound was reapplied for a third time ( Figure 5.12). RNA was harvested at t = 96 hours after plating.…”