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Authors: Schüle, Katrin Mercedes
Title: The Role of GADD45 Proteins and NEIL DNA Glycosylases in Mouse Embryonic Stem Cells
Online publication date: 24-Oct-2019
Language: english
Abstract: The establishment of DNA methylation patterns is key to ensure the epigenetic and transcriptional changes required for accurate progression during early mouse development. These DNA methylation patterns are, in contrast to longstanding presumption, dynamically regulated by a passive and an active process of DNA demethylation. The identification of TET proteins and TDG as mediators of the active DNA demethylation pathway has raised great interest in understanding their involvement in early mouse development. Our laboratory and others discovered players in active DNA demethylation. First, the GADD45 (Growth arrest and DNA damage-inducible) protein family, fulfilling a dual function by enhancing TET and TDG activity. Second, the nei endonuclease VIII-like family of DNA glycosylases (NEIL1 and NEIL2) capable to promote the substrate turnover of TDG. The precise role of GADD45 and NEIL proteins in promoting DNA demethylation during development is not well understood, and addressed in this study in two separate chapters using mouse embryonic stem cells as versatile in vitro system resembling early mouse development. Mouse embryonic stem cells (mESC) deficient for all three Gadd45 genes showed deregulation and hypermethylation of a specific subset of genes attributed to the totipotent 2-cell (2C) stage. 2C-reporter analysis corroborated GADD45 proteins as novel regulators of the 2C-like state, a mESC state with expanded fate potential comparable to the 2-cell embryo. Gadd45a/b/g deficient mESCs revealed reduced cycling into the 2C-like state resulting in reduced fate potential to transdifferentiate into trophoblast stem cells. Gene expression analysis of Gadd45a/b deficient 2-cell mouse embryos showed transcriptional changes for zygotic genome activation (ZGA) specific genes supporting the hypothesis that GADD45 proteins are involved in zygotic genome activation in vivo. Neil1 or Neil2 deficient mESCs failed to differentiate into the neuronal and neural crest lineage. Notably, this defect was not associated with their implication in active DNA demethylation, but rather with their function in base excision repair in mitochondria. Elevated mitochondrial DNA damage in Neil1 and Neil2 deficient mESCs activated an intrinsic mitochondrial p53 response impairing neuronal specification in vitro. In summary, these results highlight the importance of the proteins GADD45 alpha, beta, gamma and NEIL1,2 at distinct stages of early mouse development, and attribute their causal involvement in DNA demethylation and DNA repair, respectively.
DDC: 570 Biowissenschaften
570 Life sciences
Institution: Johannes Gutenberg-Universität Mainz
Department: Externe Einrichtungen
Place: Mainz
Version: Original work
Publication type: Dissertation
License: in Copyright
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Extent: 125 Blätter
Appears in collections:JGU-Publikationen

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