TitlePrdx1 deficiency in mice promotes tissue specific loss of heterozygosity mediated by deficiency in DNA repair and increased oxidative stress
NameRani, Vamsi K. (author), Brenneman, Mark (chair), Tischfield, Jay (internal member), Shao, Changshun (internal member), Kong, Ah-Ng Tony (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectMicrobiology and Molecular Genetics,
DescriptionLoss of the H2O2 scavenger protein encoded by the peroxiredoxin 1 (Prdx1) gene in mice leads to elevated intracellular amounts of reactive oxygen species (ROS) and promotes tumorigenesis in several different tissues. Loss of heterozygosity (LOH) mutations can initiate tumorigenesis through loss of tumor suppressor gene function in somatic cells that carry only one functional allele. A connection between the severity of oxidative stress and the frequency of LOH mutations has not been previously established in vivo. Therefore, in this study, we characterized in vivo LOH in ear fibroblasts and splenic T cells of 3-4 month old Prdx1-deficient mice. We found that loss of Prdx1 significantly elevates ROS levels in T cells and fibroblasts, and that basal levels of ROS are higher in fibroblasts than in T cells, probably due to a less robust Prdx1 peroxidase activity in the former. Using Aprt as a LOH reporter, we observed an elevation in LOH mutation frequency in fibroblasts, but not in T cells, of Prdx1-/- mice compared to Prdx1+/+ mice. The majority of the LOH mutations in both cell types were derived from mitotic recombination (MR) events. Interestingly, Mlh1, which is known to suppress MR between divergent sequences, was found to be significantly down-regulated in fibroblasts, but not in T cells, of Prdx1-/- mice. Additionally, there was no compensatory increase in expression of base excision repair (BER) genes in Prdx1-/- fibroblasts. Since these cells had higher amounts of ROS, it suggests that BER activity may be insufficient to manage the increased oxidative DNA damage load. This could lead to increased formation of SSBs and DSBs, which could require repair by recombination. A combination of increased amounts of ROS, down-regulation of Mlh1 and inefficient BER may have contributed to the elevation of MR in fibroblasts of Prdx1-/- mice. Additionally, my findings suggest that helix-distorting lesions may also be increased in Prdx1-/- ear fibroblasts and T cells. Transcription analyses of genes in different DNA repair pathways in the whole spleen tissue with Prdx1 deficiency revealed significant differences in transcription compared to T cells. I conclude that mechanisms through which Prdx1 deficiency promotes tumorigenesis in specific tissues may be distinct.
NoteIncludes bibliographical references
Noteby Vamsi K. Rani
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.