pre-implantation development; totipotency; parental specific transgenerational inheritance; epigenetics; histone methylation; Polycomb Group proteins; RNA deep-sequencing; systems biology; transgenerational; inheritance; chromatin
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.
Gill Mark E, Erkek Serap, Peters Antoine Hfm (2012), Parental epigenetic control of embryogenesis: a balance between inheritance and reprogramming?, in Current opinion in cell biology
, currently online, ---.
Véron Nathalie, Peters Antoine H F M (2011), Epigenetics: Tet proteins in the limelight., in Nature
, 473(7347), 293-4.
Brykczynska Urszula, Hisano Mizue, Erkek Serap, Ramos Liliana, Oakeley Edward J, Roloff Tim C, Beisel Christian, Schübeler Dirk, Stadler Michael B, Peters Antoine H F M (2010), Repressive and active histone methylation mark distinct promoters in human and mouse spermatozoa., in Nature structural & molecular biology
, 17(6), 679-87.
Albert Mareike, Peters Antoine H F M (2009), Genetic and epigenetic control of early mouse development., in Current opinion in genetics & development
, 19(2), 113-21.
Hotz Hans-Rudolf, Peters Antoine H F M (2009), Protein demethylation required for DNA methylation., in Nature genetics
, 41(1), 10-1.
Background: Through the modulation of chromatin states, epigenetic mechanisms contribute to the reading of genetic information. Classically, epigenetic regulators are known to play a conserved role in the heritability of cell identity during somatic differentiation and in genome stability. Recent studies showed that certain epigenetic modifiers regulate the maintenance of differentiation potential and self-renewal capacity in stem cells. In contrast, remarkably little is known about the epigenetic mechanisms regulating the acquisition of totipotency and subsequent lineage specification during early mammalian development. In mammals, fusion of an oocyte and a spermatozoon, two highly differentiated, transcriptionally silent germ cells, leads to the formation of a totipotent embryo. Epigenetic reprogramming processes occurring during gametogenesis are thought to facilitate efficient re-acquisition of totipotency in blastomeres, individual cells within early embryos, arguing for an epigenetic transgenerational contribution. Accordingly, we recently demonstrated a role for transgenerational inheritance of histone lysine methylation in the establishment of proper chromatin states and control of transcriptional repression at constitutive heterochromatin in the early embryo. Furthermore, preliminary data indicate that expression of selected genes in early embryos is regulated by distinct chromatin based repressive pathways. Another recent publication implicated histone arginine methylation in lineage determination during pre-implantation development.Hypotheses: 1.We hypothesize that epigenetic repressive mechanisms control zygotic gene activation in a parent-of-origin dependent manner in early mouse pre-implantation embryos.2.We put forward that transgenerational transmission of histone methylation controls gene specific repression in early embryos.3. We propose that epigenetic mechanisms contribute to lineage specification during mouse pre-implantation development. Aims: To test these hypotheses we propose the following specific aims:1.To investigate the role of distinct epigenetic repressive pathways in the control of zygotic gene activation in early pre-implantation embryos. Towards this goal, we will perform unbiased genome-wide expression analyses by microarray and RNA deep-sequencing methods in early embryos, wild-type or maternally and/or zygotically deficient for one or more histone methyltransferases and Polycomb Group proteins. Candidate genes will be validated by RT-qPCR. We will use DNA polymorphisms to determine the parental origin of alleles. Detection of nascent transcripts by RNA-FISH will be used to differentiate between mRNAs maternally provided or de novo transcribed from the embryonic genome in early embryos.2.To assess the functional significance of transgenerational transmission of specific histone modifications for gene activity or repression in the early embryo. We will generate transgenic mice expressing a particular histone demethylase during late stage spermiogenesis or oogenesis. Subsequently, we will study in early embryos the transcriptional and developmental consequences of absence of specific “active” or “repressive” histone modifications that are normally transmitted by paternal and/or maternal genomes at fertilization. 3.To study the contribution of specific epigenetic modifiers for lineage specification in pre-implantation embryos. We will perform genome-wide gene expression studies in pools of inner cell mass, primitive endoderm and trophectodermal cells isolated from wild-type and mutant blastocyst embryos. We will use expression of transgenic fluorescent proteins controlled by promoters of Nanog, Gata6 and Cdx to sort cells according to their cellular lineage. Distinct mutants will be studied to determine the effect of gene deficiency of epigenetic modifiers for expression and lineage specification. Expected Value: By combining Affymetrix Gene array and RNA deep-sequencing methodologies with sophisticated conditional mouse mutants and extensive bioinformatic analyses, the proposed experiments represent a systems biology approach that will generate quantitative data on transcriptional control by epigenetic master regulators during pre-implantation development. The results will lead to insights in the mechanisms of transgenerational inheritance of epigenetic information as well as in the transcriptional networks linked to the acquisition of totipotency and first lineage specification during mammalian embryogenesis. These in vivo studies will aid the elucidation of epigenetic reprogramming mechanisms implicated in the generation of induced pluripotent stem (iPS) cells in vitro.