Gene expression alterations in peripheral blood mononuclear cells of Alzheimer\'s disease patients and consequences of polymerase β deficiency in mouse fibroblasts

Author(s)

Giovana da Silva Leandro

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2016-04-07

Examining board members

Elza Tiemi Sakamoto Hojo; Carlos Renato Machado; Carlos Frederico Martins Menck

• Advisor: Elza Tiemi Sakamoto Hojo

Abstract

Alzheimer\'s disease (AD) is an age-related neurodegenerative pathology associated with a range of features such as deposition of proteins in the brain, alterations in cell cycle, accumulation of DNA damage, DNA repair deficiency and mitochondrial dysfunction. However, the molecular mechanisms implicated in the pathogenesis of AD are still uncertain. Thereby, the present study aimed to evaluate whether peripheral blood mononuclear cells (PBMCs) of AD patients display alterations in gene expression profiles, mainly focusing on processes related to cell cycle and DNA repair. Furthermore, we evaluated the implications of deficiency in polymerase ? (Pol?), which is a major polymerase involved in base excision repair (BER), in mouse embryonic fibroblasts (MEFs). Blood samples were collected from 25 AD patients and 15 age-matched controls in order to perform genome-wide mRNA and microRNA expression (microarrays). Moreover, mouse embryonic fibroblasts that are knockout for Pol? were evaluated in order to determine the effects of Pol? deficiency. In PBMCs cells, bioinformatics analysis indicated 593 mRNAs and 12 microRNAs differentially expressed in AD compared to controls. Analysis of pathway enrichment indicated that processes related to cell proliferation, DNA repair, and inflammation, among others, were altered in AD blood cells. Despite the enrichment of pathways associated with cell cycle regulation, PCNA protein expression (related to cell proliferation) analyzed by Western blot did not show difference in AD. However, Pol? expression was decreased in AD blood cells, especially in patients stricken with severe AD, in spite of the lack of alterations in terms of transcript expression. Based on the results regarding decreased Pol? expression in AD cells, we studied the consequences of Pol? knockout in MEFs, and the results clearly showed mitochondrial dysfunction along time. Thus, our study demonstrated that iv PBMCs of AD patients present alterations in cell cycle and DNA repair processes, as proposed for AD neurons, reinforcing the hypothesis that failures of DNA repair mechanisms are related to AD, and PBMCs can somehow express some of pathological conditions that may occur in neurons. We also found some genes that represent potential targets to be studied as biomarkers of the disease. Furthermore, this study demonstrated that Pol? deficiency can lead to mitochondrial dysfunction, which is an inherent characteristic of AD. (AU)

• FAPESP's process: 12/07879-5 - Evaluation of the efficiency of DNA repair mechanisms and gene expression in lymphocytes from patients with Alzheimer's Disease
• Grantee: Giovana da Silva Leandro
• Support Opportunities: Scholarships in Brazil - Doctorate