Year 2

The application of human embryonic stem cells (hESCs) requires reliable cell sources that do not change over time and initiate proper transcriptional and chromatin changes upon induction of differentiation. Therefore, it is important to understand how and when aberrancies such as the epigenetic instability of the X chromosome arise, and to define their consequences for differentiation processes and the differentiated progeny. To this end, our goal is to understand how the inactive X chromosome is regulated in human pre-implantation embryos, during derivation of hESCs from blastocysts, and during their maintenance. We have applied a large number of single cell, genome-wide, and population-wide approaches to understand this problem at a systematic and comprehensive level. Our findings define the relationship between different X-inactivation states in female hESCs and demonstrate the consequences of different X-inactivation states for hESC differentiation. Moreover, we have started to assess strategies that would prevent the instability of the inactive X chromosome and allow normal dosage compensation upon differentiation of hESCs.