Background: Nijmegen Breakage Syndrome (NBS) is a rare autosomal recessive genetic disorder, first described 1981 in Nijmegen, the Netherlands. NBS is caused by mutations in the gene coding for NIBRIN (NBN) which is involved in DNA damage repair. The MRE11-RAD50-NBN (MRN) complex binds directly to DNA double-strand breaks (DSBs).
Characteristics of NBS include genomic instability, premature aging, microcephaly, immune deficiency, extreme radiosensitivity, higher cancer susceptibility and insulin resistance. A common denominator of these conditions could be chronic oxidative stress caused by endogenous ROS overproduction and impairment of mitochondrial homeostasis. Preliminary experiments have demonstrated that patient derived induced pluripotent stem cells (iPSCs) are suitable for modelling the disease and studying DNA damage during 2D and 3D in vitro differentiation processes.
Aim: Every cell type reacts differently to genotoxic noxes. Therefore, we aim to comparatively analyse DNA damage response pathways in hepatocytes and neurons differentiated from healthy and NBS-patient derived iPSCs after subjecting them to genotoxic stress.
Experimental procedure / working programme: We will analyse the influence of ionizing radiation, Benzo(a)pyrendiolepoxid (BaP), and Aflatoxin B1 (AB1) on the iPSCs during and after differentiation. The efficiency of DNA repair and the associated stress response will be compared between stem-, progenitor-, and mature cells derived from NBS patients and healthy donors. We will analyse how genotoxic stress influences the process of neurogenesis and hepatogenesis as well as the phase I and II metabolism of hepatocytes. Transcriptome analyses will indicate cell type specific changes in signalling pathways and Gene Ontologies. Key factors of DNA damage repair, apoptosis, and proliferation will be analyses on RNA and protein level, as well as with functional assays. In addition, we will focus on neuronal migration, mitochondrial damage and hepatocyte function (CYP450 activity). The project will be accomplished in close cooperation with other members of the GRK 2578.
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