Figure 2. Xist activators and repressors regulate initiation of XCI in mESCs.

Xist levels are low in undifferentiated mESCs before onset of XCI, because of pluripotency transcription factors repressing Xist directly or indirectly via Tsix. X-linked Xist activators increase Xist levels during differentiation, as they themselves are upregulated. Levels of autosomal factors such as pluripotency transcription factors decrease upon differentiation. Sizes and positions of weights are reflective of magnitude of Xist-up or downregulation phenotypes from experimental data (see text for discussion).