Epitranscriptomic regulation of meiosis and the preimplantation embryo

Dynamic modifications in protein and DNA have been studied for decades and are crucial for maintaining homeostasis in the human body. Such "epigenetic" regulation is the reason why a skin cell can be so different from e.g. a brain cell. The dynamic regulation of chemical modification in RNA is a much more recent discovery (2011) and 6-methyladenine (m6A) is the best studied RNA modification. Preliminary data indicate key role of this modification in neuronal development and fertility (meiosis). Recent studies also find m6A to be dynamically regulated in cancer. In this project we will analyse the role of 6-methyladenine in disease. We will also generate novel reporter organisms and systems for studying how these methylation marks in RNA is introduced and removed. Our ultimate goal is to identify how writers, readers and erasers of this modification and to understand how they regulate differentiation, neuronal development and disease. Our new data indicate that this modicifation also regulate genome stability by being a part of the so-called R-loop structure and we are currently studying if this affect recombination early during development. In order to get a more complete picture on the regulatory modifications we also study histone modifications co-regulated with m6A in mRNA

The main aim is to gain mechanistic insight of meiosis and the early embryo - and to publish in renowned journals for a large scientific community. Several manuscripts have been published or are in revision (results report). Main findings include: - The maternal-zygotic-transition (MZT) depends on a coordinated action of several histone marks. - m6A marks on mRNA is required for balancing RNA/DNA hybrids and genome stability. - m6A marks on mRNA regulate the expression of retrotransposons. - m6A marks on mRNA is highly dynamic during the early embryo development. A successful project also relies on the advancement of methods for single-cell identification of histone and RNA marks. These methods will be valuable for analyzing cancer heterogeneity. Patents appl. include: 1. Chip-seq assays; Dahl and Klungland (US Patent App 16/328,909) 2. Kits for detection of methylation status; Dahl et al (US Patent App 11,078,529)

A broad repertoire of chemical modifications is known to underlie adaptable coding and structural function of proteins, DNA and RNA. Methylations of mammalian DNA and histone residues are known to regulate transcription and the discoveries of demethylases that remove methylation in DNA and histones has led to a tremendous progress in the understanding of dynamic methyl marks in gene regulation and role in numerous diseases. Post-transcriptional RNA modifications were discovered several decades ago, but the reversible nature of RNA modifications, discovered by Chuan He's lab and our group has only recently been discovered. Owing to technological advances, knowledge of epitranscriptomic marks and their writers, readers and erasers has recently advanced tremendously. The reliance on presynthesized RNAs is a unique feature of meiosis and shortly after fertilization, embryos cross a stage during which developmental control is handed from maternally supplied gene products from the mature oocyte to gene products synthesized from the zygotic genome. Preliminary studies in model organisms assign unique roles for dynamic mRNA modifications in meiosis and for the precise configuration of the early embryo. We here propose to study in detail the role of dynamic and reversible methylations of RNA from the primordial oocyte through meiosis to the mature oocyte and in the preimplantation embryo. Our studies will focus on the role of readers and erasers of these dynamic methyl marks. Our, and others, recent data on the role of mRNA demethylation in meiosis and that of our collaborator, Chuan He, on the modification dependent clearance of maternal mRNAs for correct timing of MZT is very inspiring.