Relevance of oxidative stress in induced pluripotent cells and neural progenitors derived from Cockayne Syndrome patients

Abstract

Genome stability is threatened by a huge range of intrinsic and extrinsic agents, which interact and damage the DNA molecule. The biology dogma, replication and transcription, is compromised in the presence of these DNA lesions. To deal with these lesions, evolutively well-conserved DNA repair mechanisms are present among all living beings. Nucleotide Excision Repair (NER) is one of them and it is responsible for resolving bulky lesions on DNA caused by ultraviolet light (UV) and, to certain extent, oxidative stress. One part of the DNA strand containing the lesion is excised, and the other is used as a template for filling the created gap. The absence of any NER factor can lead to severe human syndromes associated either with high cancer predisposition and/or severe neurodevelopment abnormalities, this last one associated with premature aging. Cancer predisposition in these syndromes is long known as due to increased mutation rates caused by the DNA repair defects upon UV induced lesions. Still, neurological abnormalities are believed to be caused by oxidative stress in a not very well understood manner. Cockayne Syndrome (CS) is a NER syndrome characterized by neurological abnormality, neurodegeneration, growth failure and photosensitivity, but patients are not cancer prone. Skin fibroblasts (primary or transformed) are the main study model for this syndrome, but they do not fully represent the complexity of the - most affected - neural tissue. Our preliminary data, using cellular reprogramming technology, showed increased sensitivity to oxidative stress in induced Pluripotent Cells (iPSC) and Neural Progenitors (NPC) of CS patients when compared to their primary isogenic fibroblasts. These results indicate that the neurological abnormalities of CS patients may be due to the neural tissue sensitivity to oxidative stress. Our aim is to understand the responses of induced Pluripotent Stem Cells (iPSC), Neural Progenitor Cells (NPC) and neurons from CS patients to different conditions of oxidative stress, and oxygen tension, comparing with DNA repair proficient cells. We intend to evaluate, not only sensitivity itself, but also the formation and eventual repair of lesions induced in the DNA of these cells. The effects of different oxygen tension conditions on the differentiation process of NPC cells in functional neurons should also be investigated. Our expectation is to better understand the clinical degenerative phenotype of CS patients and their relation to DNA lesions. (AU)