O-GlcNAcylation of Sox2 at threonine 258 regulates the self-renewal and early cell fate of embryonic stem cells.

Sox2 is a core transcription factor in embryonic stem cells (ESCs), and O-GlcNAcylation is a type of post-translational modification of nuclear-cytoplasmic proteins. Although both factors play important roles in the maintenance and differentiation of ESCs and the serine 248 (S248) and threonine 258 (T258) residues of Sox2 are modified by O-GlcNAcylation, the function of Sox2 O-GlcNAcylation is unclear. Here, we show that O-GlcNAcylation of Sox2 at T258 regulates mouse ESC self-renewal and early cell fate. ESCs in which wild-type Sox2 was replaced with the Sox2 T258A mutant exhibited reduced self-renewal, whereas ESCs with the Sox2 S248A point mutation did not. ESCs with the Sox2 T258A mutation heterologously introduced using the CRISPR/Cas9 system, designated E14-Sox2, also exhibited reduced self-renewal. RNA sequencing analysis under self-renewal conditions showed that upregulated expression of early differentiation genes, rather than a downregulated expression of self-renewal genes, was responsible for the reduced self-renewal of E14-Sox2 cells. There was a significant decrease in ectodermal tissue and a marked increase in cartilage tissue in E14-Sox2-derived teratomas compared with normal E14 ESC-derived teratomas. RNA sequencing of teratomas revealed that genes related to brain development had generally downregulated expression in the E14-Sox2-derived teratomas. Our findings using the Sox2 T258A mutant suggest that Sox2 T258 O-GlcNAc has a positive effect on ESC self-renewal and plays an important role in the proper development of ectodermal lineage cells. Overall, our study directly links O-GlcNAcylation and early cell fate decisions.