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Resumen Los microRNA (miRNA) son pequeños RNA no codificantes de aproximadamente 17 a 24 nucleótidos de longitud, los cuales se unen complementaria y principalmente en las regiones 3' UTR (región no traducida) de diversos RNA mensajeros (mRNA, messenger RNA). Su función general es regular negativamente la expresión génica a nivel postranscripcional, inhibiendo la traducción. Perfiles de expresión de miRNA alterados han sido identificados en diferentes líquidos, células y tejidos humanos afectados con diversas enfermedades autoinmunes y algunos se han propuestos potencialmente como biomarcadores de diagnóstico, pronóstico, actividad, etcétera, en estas patologías. Adicionalmente, variantes comunes del genoma humano, denominados polimorfismos de un solo nucleótido (SNP, single nucleotide polymorphisms) localizados en genes de miRNA han sido asociados con susceptibilidad, gravedad, y actividad en estas enfermedades. El objetivo de esta revisión es describir la biogénesis de los miRNA, su función, así como los perfiles de expresión y SNP en genes de miRNA asociados con diversas enfermedades autoinmunes, incluyendo tiroiditis autoinmune (tiroiditis de Hashimoto y enfermedad de Graves), lupus eritematoso sistémico, artritis reumatoide y síndrome de Sjögren primario.

Abstract MicroRNAs (miRNAs) are small non-coding RNAs of approximately 17-24 nucleotides in length, which complementarily and mainly bind in 3' UTR (untranslated region) regions of different messenger RNAs (mRNAs). Their general function is to negatively regulate gene expression at the posttranscriptional level, thus inhibiting translation. miRNA abnormal expression profiles of have been found in different human fluids, cells and tissues affected by different autoimmune diseases, and some of them have been proposed as potential biomarkers of diagnosis, prognosis, activity etc. in these pathologies. In addition, common variants of the human genome, called single-nucleotide polymorphisms (SNPs), located within miRNA genes, have been associated with susceptibility, severity and activity in these diseases. The purpose of this review is to describe miRNA biogenesis and function, as well as the expression profiles and SNPs in miRNA genes that are associated with different autoimmune diseases, including autoimmune thyroiditis (HashimotoMs thyroiditis and Gravess disease), systemic lupus erythematosus, rheumatoid arthritis and primary Sjögren's syndrome.

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OBJECTIVE: The aim of the study was to evaluate the association of miRNA-146a G/C (rs2910164), and miRNA-196a2 C/T (rs11614913) polymorphisms with the presence of coronary artery disease (CAD) and/or restenosis in patients with coronary stent. MATERIALS AND METHODS: The polymorphisms were determined in 218 patients with CAD who underwent coronary artery stenting (66 with restenosis and 152 without restenosis) and 611 healthy controls using 5' exonuclease TaqMan assays. RESULTS: The distribution of both polymorphisms was similar in patients with and without restenosis. However, when the whole group of patients (with and without restenosis) was compared to healthy controls, under co-dominant, dominant and additive genetic models, the T allele of the miRNA-196a2 C/T (rs11614913) polymorphism was associated with increased risk of CAD (OR = 2.18, Pco-dom = 0.006, OR = 1.86, Pdom = 0.002, and OR = 1.52, Padd = 0.002, respectively). All models were adjusted for age, type 2 diabetes mellitus, dyslipidemia, hypertension and smoking habit. The "GT" haplotype was associated with increased risk of developing CAD (OR = 1.36, P = 0.046). CONCLUSIONS: Our data suggests that the T allele of the miRNA-196a2 C/T (rs11614913) polymorphism is associated with the risk of developing CAD, but no association with restenosis was observed.

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Recently, different microRNA (miRNA) gene polymorphisms have been evaluated in patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and Graves' disease (GD). In the present study, we examined three single-nucleotide polymorphisms (SNPs) located in the pre-miR-146a (rs2910164G/C), pre-miR-196a-2 (rs11614913C/T), and pre-miR-499 (rs3746444A/G) genes. Our study population included 900 Mexican patients with RA, SLE, or GD, as well as 486 healthy control individuals with no family history of inflammatory or autoimmune diseases. Genotyping was performed using TaqMan probes and a 5' exonuclease assay. None of the investigated SNPs were associated with RA or GD susceptibility under any genetic model (co-dominant, recessive, or dominant). Genotype and allele frequencies of the miR-196a-2 rs11614913C/T polymorphism were similar between SLE cases and controls. In contrast, the miR-146a rs2910164G/C and miR-499 rs3746444A/G polymorphisms were associated with SLE susceptibility. These SNPs were not associated with lupus nephritis (LN). Our results suggest that polymorphisms in miR-146a, miR-196a-2, and miR-499 are not associated with RA or GD susceptibility. This is the first report documenting that the miR-146a rs2910164G/C and miR-499 rs3746444 polymorphisms are associated with SLE susceptibility but not with LN.

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Single nucleotide polymorphisms (SNPs) represent the most common type of variation in the human genome. The SNPs located in protein-coding and non-coding RNA genes are classified as neutral and functional. The neutral have no effect, while the functional affect different biological processes and continually confer risk for multifactorial diseases. Functional SNPs found in the promoters of protein-coding and non-coding RNA genes (microRNAs: miRNAs) termed regulatory SNP (rSNPs) and miRNAs rSNPs (miR-rSNPs), respectively, affect the gene expression. Functional SNPs located on the structure of the precursor mRNAs (exons and introns), mature mRNA (5´ untranslated region [UTR], coding sequence, and 3´ UTR), and primary, precursor, and mature miRNAs are termed structural RNA SNPs (srSNPs) and miR-srSNPs, respectively. The srSNPs affect the splicing (and alternative splicing), srSNPs affect the splicing (and alternative splicing), the translation, stability, amino acid sequence, structure, and function of proteins and interaction between mRNA/miRNAs. Finally, the miR-srSNPs affect the structure, processing and interaction between miRNAs/mRNAs. Functional characterization of potentially harmful risk alleles of the SNPs located in protein-coding and non-coding RNA genes have contributed to an understanding of their functions in the complex diseases. The objective of this review is update the reader on the functional role of the SNPs located in protein-coding and non-coding RNA genes and their relationship with multifactorial diseases.

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