Even as early as embryonic development, one of the two X chromosomes is epigenetically deactivated in female mammals. This happens so that genes are not read twice. Such “dosage compensation” is essential for healthy development. Until recently, the effects of epigenetic changes in the sex-chromosomes were not well-understood. A research team led by Hendrik Stunnenberg from Nijmegen studied embryos of female mice to better understand the functional consequences of epigenetic change.
The researchers found that the genes from the central region of the X chromosome are being deactivated to avoid overcompensation, the genes on the other X chromosome are active. In addition, a few genes in the “breakaway zones” are excluded from the inactivation and remain switched-on during the entirety of development. They are mainly located in regions that had previously supported one another (topologically associated domains, TADs). Evidence supports that such functional effects occur in human development as well.
Source: http://www.newsletter-epigenetik.de/Read more