The role of Pcgf6 function in ES cells and at the exit of pluripotency

• Applicant: Privatdozent Dr. Matthias Becker, since 9/2019
• Subject Area: Developmental Biology ; Evolutionary Cell and Developmental Biology (Zoology)
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 313642360

Polycomb group (PcG) proteins comprise evolutionary conserved factors of the molecular memory system with essential functions for embryonic development and adult stem cells. PcG proteins constitute two main multiprotein polycomb repressive complexes (PRC1 and PRC2) that operate in a hierarchical manner to silence gene transcription. For PRC1 recent data indicate that the composition and assembly are more diverse than originally estimated and that functionally distinct PRC1 variants are defined by Polycomb group RING finger protein (Pcgf) paralogs. So far, six Pcgf paralogs (Pcgf1-6) have been identified. The functions of individual Pcgf paralogs and of PRC1 variants remain elusive. Recently we showed that Pcgf 6 (alias Mblr) is the only Pcgf paralog with high expression in undifferentiated ESCs und that upon differentiation Pcgf6 expression declines. Following Pcgf6 knockdown (KD) in ESCs the expression of core pluripotency genes, ESC colony formation and colony sizes were decreased, while lineage-specific genes were de-repressed. Concomitantly, differentiating Pcgf6 KD ESCs increased hemangioblastic and hematopoietic differentiation activities suggesting a Pcgf6 function in early differentiating ESCs. Consistent with a role in pluripotency, Pcgf6 replaced Sox2 in the generation of germline-competent iPS cells. Here it is planed to characterize the exit of pluripotency by assessing Pcgf6 chromatin binding and Pcgf6 complex partners. Specifically it is proposed 1.) to determine the genomic binding sites of Pcgf6 in ESCs, epiblast stem cells (EpiSCs), and in ESC-derived embryoid bodies (EBs), 2.) to characterize Pcgf6 protein interactions, 3.) to elucidate whether in ESCs Pcgf6 is part of PRC1 or not and 4.) to characterize the Pcgf6 domain functions. Understanding Pcgf6 biology at the molecular level is an important step forward in defining the critical molecular determinants of ESC pluripotency and for the exit of pluripotency.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Albrecht M. Müller, until 9/2019 (†)