Quantification of microRNAs in the central nervous system : implications / Quantificação de diferentes microRNAs no sistema nervoso central : implicações nos mecanismos de desenvolvimento e processos fisiopatologicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

MicroRNAs are a new class of small RNA molecules (21-24 nucleotide-long) that negatively regulate gene expression either by translational repression or target mRNA degradation. It is believed that about 30% of all human genes are targeted by these molecules. MiRNAs are involved in many important biological processes including cell differentiation, embryonic development and central nervous system formation, besides they showed specific temporal-space expression. They can regulate 1/3 of human genes and are involved in metabolism and apoptosis. miRNAs are the key as neurogenesis postranscriptional regulation; studies previous indicates miRNA expression associate with proliferation and differentiation in development of central nervous system (CNS) and housekeeping expression in mature neurons. They are involved in several diseases as Alzkeimer s and Parkinson and may have a role in epilepsy regulation. In second chapter, we analyze the miRNA expression in mouse brain during four stages of CNS development; in third chapter, we analyze hippocampal tissue of four patients who underwent selective resection of the mesial temporal structures for the treatment of clinically refractory seizures. In addition we used control samples from autopsy (n=4) for comparison. In both experiments, total RNA was isolated from tissues and used in real-time PCR reactions with TaqMan¿ microRNA assays (Applied Biosystems) to quantify 104 (mouse brain) or 157 (human tissue) different miRNAs. In mouse brain analysis, we were able to identified four different clusters (C1, C2, C3 and C4) of miRNAs expression. Significant differences in expression during development were observed only in miRNAs included in C1. Our results suggest the presence of a specific expression pattern in C1, indicating that these miRNAs could have an important role in gene regulation during neurogenesis. We found a significant decrease (p<0,05) in expression of 12 miRNAs (miR-9; miR-17-5p; miR-124a; miR-125a; miR-125b;miR-130a; miR-140; miR-181a; miR-199a; miR-205; miR-214; miR- 301) belonging to cluster C1 in latter stages of development. Computational target identification showed that 10 of the 12 miRNAs present in C1 could be involved in neurogenesis. In human tissues, bioinformatics analyzes identified three miRNAs species which were differently expressed in patients as compared to controls: let7a was over expressed in patients (4 fold increased), miR-29b and miR-30d were down-regulated in patients (2.5 fold and 0.5 fold decreased, respectively). Possible target genes for let-7a are NME6 and NCAM1 (which would be down-regulated in patients); for miR-29b is MCL-1 and for miR30d are CTNND2, LGI1 and SON (which would be up-regulated in patients). We have identified three different miRNA species differently expressed in hippocampal sclerosis. Gene functions related to the possible miRNA targets are involved mainly with cell proliferation, neurogenesis, cell adhesion and apoptosis. Our results indicate new molecular targets which should be explored in additional studies addressing miRNA regulation in hippocampal sclerosis

ASSUNTO(S)

epilepsy epilepsia microrna micrornas neurogenetica neurogenetics

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