miR-9 and miR-29 in Alzheimer’s disease: assessment of a possible synergy

• Autor(a) principal: Rodrigues, Joana Filipa Soares
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/6566
• topic: Cancro da Mama; Lógica Fuzzy; Mamografia.; Método de Inferência de Mamdani; Domínio/Área Científica::Ciências Médicas::Ciências da Saúde

Alzheimer’s disease (AD) is rising as a problem with epidemic proportions. In the latest years, promising genetic therapy technology has evolved with focus on microRNAs (miRNAs) as therapeutic agents since they can be used as translation repressors or messenger RNA (mRNA) degrading agents. This property can be exploited and applied to regulate the expression of some target proteins. AD and its possible treatment with miRNA technology is in the spotlight. Several studies in the literature have reported the link between two miRNAs, the miR-9 and the miR-29, and two important proteins, namely Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) and Presenilin (PSEN), which are part of the amyloidogenic pathway. Since the amyloid-ß peptides (Aß) start to excessively accumulate, due to the increased activity of the previously mentioned proteins, the amyloid plaque is formed. Actually, at the moment this is identified as one of the main causes of the disease. Recently, our group has studied the translation repression of human BACE1 by nanoparticle-mediated delivery of recombinant pre-miR-29 into neuronal cells. Therefore, the main goal of this project was also studying the effect of pre-miR-9 in BACE1 and PSEN expression levels and to assess the possible synergy between both of the nucleic acids. Briefly, recombinant pre-miR-9 and pre-miR-29 were produced by Escherichia coli (E. coli) DH5a. Afterwards, the small RNA (sRNA) fraction was extracted by the guanidinium thiocyanate-phenol-chloroform RNA isolation protocol and purified by arginine affinity chromatography, using NaCl stepwise gradients. Both pre-miRNAs were purified by two distinct methods: a stepwise gradient with three steps and a stepwise gradient with two steps. Even though the stepwise gradient with three steps allowed the purification of both miRNAs, higher recovery was achieved when using the two stepwise gradients. The purified nucleic acids were then encapsulated into chitosan (CS) nanoparticles and used to transfect N2a695 cell lines. The efficacy of the translation inhibition of the BACE1 and PSEN mRNAs was assessed by quantitative real-time polymerase chain reaction (RT-qPCR) being demonstrated a decrease in BACE1 and PSEN mRNAs levels in the transfected cells whereas no significant difference in the control cells was observed. Mir-9 induced a greater BACE1 and PSEN mRNA inhibition than pre-miR-29, comparing to untreated control cells. In particular, BACE1 mRNA levels suffered a 42% of reduction after cells transfection with pre-miR-9 and 22% inhibition for pre-miR-29. For PSEN mRNA, it suffered 59% inhibition by pre-miR-9 and 14% inhibition by pre-miR-29. This study allowed the understanding of the effects of pre-miR-9 and pre-miR-29 on mRNAs and protein levels involved in the amyloidogenic pathway.