Maintenance of pluripotency by Polycomb proteins and stable repression of homeotic selector genes

• Applicant: Dr. Achim Breiling
• Subject Area: Hematology, Oncology
• Term: from 2008 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 65328492

The understanding of the mechanisms that regulate exit from pluripotency is fundamental to enhance our knowledge on stem cell stability. Treatments that induce differentiation in cancer stem cells also represent novel approaches to eliminate such malignant cell populations. We found that certain nucleoside analogues induce differentiation in the stem cell model NTERA 2 D1. This drug-induced differentiation is triggered by drugdependent DNA-damage or cellular stress, which causes caspase activation, and results in proteolytic depletion of stem cell factors. Among these, we found OCT4 to be a direct target of CASPASE-7. In the second funding period we will further characterise the caspase cleavage sites of OCT4 and assay whether caspase-resistant OCT4 can rescue induced differentiation and if it enhances the generation of iPS cells. Further, we will analyse the roles of initiator caspases, p53 and its upstream kinases in these processes. Lastly, we will map epigenetic changes, in particular on the level of DNA-methylation, during induced differentiation. The aim of the proposed projects is to further characterise the mechanisms that define exit of pluripotency and to identify factors and DNA elements important for the epigenetic maintenance of pluripotency, but also the induction of differentiation.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1356: Pluripotency and Cellular Reprogramming