X chromosome inactivation protects early female cells

Around the time a female embryo implants in the uterus, its cells normally switch off one of their two X chromosomes. How this process unfolds and whether it is essential for further development has remained unclear in humans. Researchers from KU Leuven and Institute Curie have now shown, using human stem cell models, that the RNA molecule XIST controls X chromosome inactivation and that placental cells do not survive properly when this inactivation fails.