A symmetric toggle switch explains the onset of random X inactivation in different mammals

Gene-regulatory networks control the establishment and maintenance of alternative gene-expression states during development. A particular challenge is the acquisition of opposing states by two copies of the same gene, as in the case of the long non-coding RNA Xist in mammals at the onset of random X-chromosome inactivation (XCI). The regulatory principles that lead to stable mono-allelic expression of Xist remain unknown. Here, we uncover the...