totipotency; embryonic stem cell; Polycomb group protein; Epigenetic inheritance; Lineage specification; Pre-implantation development
Tardat Mathieu, Albert Mareike, Kunzmann Rico, Liu Zichuan, Kaustov Lilia, Thierry Raphael, Duan Shili, Brykczynska Urszula, Arrowsmith Cheryl H, Peters Antoine H F M (2015), Cbx2 Targets PRC1 to Constitutive Heterochromatin in Mouse Zygotes in a Parent-of-Origin-Dependent Manner., in Molecular cell
, 58(1), 157-71.
Hisano Mizue, Erkek Serap, Dessus-Babus Sophie, Ramos Liliana, Stadler Michael B, Peters Antoine H F M (2013), Genome-wide chromatin analysis in mature mouse and human spermatozoa., in Nature protocols
, 8(12), 2449-70.
Nestorov Peter, Tardat Mathieu, Peters Antoine H F M (2013), H3K9/HP1 and Polycomb: two key epigenetic silencing pathways for gene regulation and embryo development., in Current topics in developmental biology
, 104, 243-91.
Erkek Serap, Hisano Mizue, Liang Ching-Yeu, Gill Mark, Murr Rabih, Dieker Jürgen, Schübeler Dirk, van der Vlag Johan, Stadler Michael B, Peters Antoine H F M (2013), Molecular determinants of nucleosome retention at CpG-rich sequences in mouse spermatozoa., in Nature structural & molecular biology
, 20(7), 868-75.
Yokobayashi Shihori, Liang Ching-Yeu, Kohler Hubertus, Nestorov Peter, Liu Zichuan, Vidal Miguel, van Lohuizen Maarten, Roloff Tim C, Peters Antoine H F M (2013), PRC1 coordinates timing of sexual differentiation of female primordial germ cells., in Nature
, 495(7440), 236-40.
Salvaing Juliette, Posfai Eszter, Peters Antoine H F M, Beaujean Nathalie (2012), [Crucial role of Polycomb proteins from maternal origin in mouse early embryonic development]., in Médecine sciences : M/S
, 28(12), 1047-9.
Gill Mark E, Erkek Serap, Peters Antoine H F M (2012), Parental epigenetic control of embryogenesis: a balance between inheritance and reprogramming?, in Current opinion in cell biology
, 24(3), 387-96.
Posfai Eszter, Kunzmann Rico, Brochard Vincent, Salvaing Juliette, Cabuy Erik, Roloff Tim C, Liu Zichuan, Tardat Mathieu, van Lohuizen Maarten, Vidal Miguel, Beaujean Nathalie, Peters Antoine H F M (2012), Polycomb function during oogenesis is required for mouse embryonic development., in Genes & development
, 26(9), 920-32.
BackgroundMammalian development starts by fusion of two highly differentiated germ cells and formation of the totipotent embryo. Mouse embryonic stem cells (ESCs) are pluripotent cells that can be derived from pre-implantation embryos at different stages of their development. In ESCs, cell identity is primarily regulated by transcription factors, e.g. Oct3/4, Sox2, and Nanog that are considered master regulators of pluripotency in vivo and in vitro and share many target genes. Gene transcription occurs, however, in the context of chromatin that serves either potentiating or restricting functions. As such, chromatin-based mechanisms contribute to the translation of genetic information. A large number of studies have shown that chromatin modifiers play a conserved role in the heritability of cell identity during somatic differentiation and in safeguarding genome stability. Since such transmission of information occurs in absence of changes in the underlying genetic code, this type of inheritance is referred to as “epigenetic”. Polycomb group (PcG) proteins are evolutionarily conserved chromatin factors that mediate gene repression. In mammals, they function in at least two different multi-protein complexes, called Polycomb Repressive Complex (PRC) 1 and 2, that mediate mono-ubiquitination of H2A at lysine 119 (H2AK119u1) and H3K27me3 respectively. These complexes typically repress genes with key regulatory functions in development and differentiation. Double-deficiency for the PRC1 paralogues, Ring1b/Rnf2 and Ring1a, causes a loss of ESC identity. Similarly, double deficiency for the core PRC1 components Ring1a and Ring1b/Rnf2 causes a developmental arrest around the eight-cell stage (unpublished data). Thus, as in ESCs, PRC1 function seems to be required for the development of totipotency during early embryogenesis. This grant application focuses on the targeting mechanisms of the PRC1 and their role in regulating cell identity of ESCs. In particular, it proposes to study the function of a family of Cbx proteins, components of PRC1, for targeting of PRC1 to chromatin and possibly specific sets of genes. These proteins contain a chromo domain that has affinity for methylated histones. The work proposed will assess to function of these chromo domains for PRC1 targeting. Furthermore, it concentrates on PRC1 function during early embryogenesis at the time of the first and second lineage decisions that ultimately give rise to the pluripotent inner cell mass and the two differentiation lineages (trophectoderm and primitive endoderm).Hypotheses1: We propose that the five different Cbx proteins contribute to target selection and specification of cell identity. We put forward that target specification is mediated, in part, by the CD of the different Cbx proteins. Furthermore, we propose that Cbx2 functions to inhibit binding of PRC1 complexes to H3K9 methylated chromatin, thereby contributing to partitioning of mammalian genomes ac-cording to epigenetic states.2: We hypothesize that the PRC1 complex and its component Cbx2 play important roles in regulating gene expression in early embryos, during the so-called maternal-to-zygotic transition in which transcription becomes activated in a largely genome-wide manner and during subsequent lineage specification. Cbx7 may be important for embryonic development towards the blastocyst stage.To investigate these hypotheses, we propose the following aims:1: To investigate the role of Cbx2, Cbx4, Cbx6, Cbx7, and Cbx8 in specifying PRC1 targeting and cell identity of undifferentiated and differentiating embryonic stem cells. 2: To assess the role of chromo domains of Cbx proteins in chromatin targeting of PRC1. 3: To determine the function of PRC1 and Cbx proteins in early embryogenesisPossible applicationsThe proposed work represents a systematic approach to dissect the mechanisms of transcriptional control by Polycomb group proteins in regulating cell identity of embryonic stem cells and during pre-implantation development. The anticipated results will provide insights into the controlling of transcriptional networks functioning in early embryos that direct the acquisition of totipotency (early stages) and drive differentiation into the first cellular lineages (later stage embryos). The mechanistic understanding obtained in these in vitro and vivo studies will aid the elucidation of epigenetic reprogramming mechanisms implicated in the generation of induced pluripotent stem (iPS) cells in vitro. As such, this work is expected to significantly contribute to studies on reprogramming of differentiated cells for therapeutic usage.