title: Phenotyping the potential antagonistic knock-out of the chromatin remodeler EZH2 and CHD7 in neural stem cells and the adult brain
creator: Jansen, Malin Insa
subject: ddc-570
subject: 570 Life sciences
description: CHARGE syndrome describes a combination of severe developmental defects including, among other things, a delayed or retarded mental development, sometimes combined with a variety of psychological symptoms. Especially, the molecular mechanisms behind this brain phenotype is little understood, and cannot be treated effectively up to now.  This syndrome is caused by a heterozygous mutation in the Chromodomain helicase protein 7 (chd7) gene, which encodes an epigenetically active protein (CHD7) mediating nucleosome sliding, and associated with open and active chromatin (H3K27ac, Feng et al., 2017).  Another epigenetically active protein fulfilling an opposite task is EZH2 (the catalytic part of the polycomb repressive complex 2 (PRC2)) which silences gene expression by methylating histon 3 lysin 27. Both EZH2 and CHD7 are expressed in overlapping brain regions, and a knock-out of the respective protein has opposing effects on neuronal branching (Feng et al., 2013 and Liu, Y.). With these hints it was hypothesized that EZH2 might counteract CHD7 deficiency and could be beneficial for the CHARGE condition.  In the frame of this thesis I was able to generate and analyze a CHARGE mouse (CMVCre;CHD7+/fl) that displayed a variety of CHARGE related symptoms. Heterozygous chd7 mutant mice had a reduced body weight, were significantly more active, developed sever eye malformations with narrowed palpebral fissures, significantly smaller eye diameter, a thinner retina and inner nuclear layer, and partially completely dysfunctional eyes. Furthermore, the cerebellum of CHARGE mice showed a missing anterior lobe, and a disorganized purkinje cell layer with less primary branches. Also CHARGE mice have less neurogenesis ind the hippocampus.  Following the main hypothesis a genetic rescue (CMVCre;CHD7+/fl;EZH2+/fl) could restore; body and brain size, the strong eye malformations observed under CHARGE conditions, the amount of neural stem cells in the dentate gyrus, and the cerebella purkinje cell layer. Moreover, an RNA sequencing of the cerebellum tissue revealed that the gene expression of many genes in the double knock-out was indeed rescued. Furthermore, a homozygous inducible double knock-out of chd7 and ezh2 (NesCreERT2;CHD7fl/fl;EZH2fl/fl) rescued the neural stem cell pool in comparison to a chd7 single knock-out.  Finally, these findings encourage me to use a very potent EZH2 inhibitor to treat neural stem cells in vitro and in vivo, thus attempting a novel CHD7 deficient treatment.
date: 2020
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/29128/1/Thesis.pdf
identifier: DOI:10.11588/heidok.00029128
identifier: urn:nbn:de:bsz:16-heidok-291287
identifier:   Jansen, Malin Insa  (2020) Phenotyping the potential antagonistic knock-out of the chromatin remodeler EZH2 and CHD7 in neural stem cells and the adult brain.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/29128/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng