Gene Expression Profiles and Possible Interactions between microRNAs and mRNAs in Type 1 Diabetes Mellitus, Focusing on Response to Oxidative Stress and DNA Repair

Author(s)

Paula Takahashi

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto
• Defense date: 23 mar. 2015

Examining board members

Elza Tiemi Sakamoto Hojo; Carlos Renato Machado; Nilce Maria Martinez Rossi; Daisy Maria Fávero Salvadori; Zila Luz Paulino Simoes

• Advisor: Elza Tiemi Sakamoto Hojo

Abstract

Type 1 Diabetes Mellitus (T1DM) results from an autoimmune attack against the pancreatic cells, ceasing insulin production, which causes hyperglycemia. Although associations between oxidative stress, which can cause DNA damage, and T1DM have been demonstrated, only a few studies have reported differential expression of genes associated with response to oxidative stress and DNA repair in T1DM patients. Moreover, microRNAs (post-transcriptional regulators of gene expression) are implicated in many biological processes and pathological conditions; however, only scarce information is available in the literature concerning the expression of microRNAs in T1DM. In order to better understand the regulatory pathways involved in biological processes that are relevant to T1DM, we aimed to investigate the microRNA and mRNA transcriptional expression profiles by microarray analysis (as well as expression of selected proteins) in peripheral blood mononuclear cells (PBMCs) from T1DM patients (n=19) compared with healthy non-diabetic individuals (n=11), emphasizing genes related to response to oxidative stress and DNA repair. Microarray expression results indicated 44 differentially expressed microRNAs (35 up- and nine down-regulated) in T1DM patients, with those microRNAs possessing a discriminatory power to clearly stratify the patients from the controls, including hsa-miR-101, hsa-miR148a, hsa-miR-27b, and hsa-miR-424, whose expression data were confirmed by qRT-PCR. Functional annotation analysis performed on the predicted targets of the differentially expressed microRNAs pointed 22 and 12 annotated KEGG pathways for the overexpressed and repressed microRNAs, respectively, many of them related to cancer. Regarding mRNA microarray results, we detected 277 differentially expressed genes in T1DM patients, with 52% of them being potential targets of the differentially expressed microRNAs in T1DM patients. Among these targets, we identified candidate genes for T1DM as well as genes involved in the biological processes response to oxidative stress and DNA repair, such as UCP3, PTGS2, ATF3, FOSB, DUSP1 and TNFAIP3, whose expression data were confirmed by qRT-PCR. Furthermore, out of the 49 and 55 significantly expressed/enriched gene sets in T1DM patients, respectively, five pathways related to apoptotic signaling, response to hydroperoxide, DNA repair via homologous recombination, and response to endoplasmic reticulum stress were of interest for the present work. Concerning protein expression results (western blotting), PTGS2 and ATF3 expression was not detected for either the patient or the control group, while significant difference in DUSP1 expression was not observed between the two groups, although the corresponding mRNAs of those genes were found induced. Regarding the luciferase assay, our results demonstrated that the interaction between hsa-miR-148a and DUSP1 occurs in the cellular milieu. Therefore, these findings together with those western blotting results suggest that hsa-miR-148a could play a role in DUSP1 translational repression. Altogether, our results indicate distinctive microRNA and mRNA expression profiles in PBMCs from T1DM patients relative to healthy non-diabetic individuals. Furthermore, we have provided novel data regarding microRNA-mRNA interactions in T1DM, in particular involving genes associated with response to oxidative stress and DNA repair, suggesting a perturbation in the microRNA-target network in T1DM patients. (AU)

• FAPESP's process: 10/12069-7 - Gene expression profiles and possible interactions between microRNAs and mRNAs in type 1 Diabetes Mellitus, focusing on response to oxidative stress and DNA repair
• Grantee: Paula Takahashi
• Support type: Scholarships in Brazil - Doctorate