ABSTRACT
IL-6 is an inflammatory cytokine and its overexpression plays an important role in osteoarthritis (OA) pathogenesis. Expression of IL-6 is regulated post-transcriptionally by MCPIP1. The 3' untranslated region (UTR) of MCPIP1 mRNA harbors a miR-139 'seed sequence', therefore we examined the post-transcriptional regulation of MCPIP1 by miR-139 and its impact on IL-6 expression in OA chondrocytes. Expression of miR-139 was found to be high in the damaged portion of the OA cartilage compared with unaffected cartilage from the same patient and was also induced by IL-1beta in OA chondrocytes. Inhibition of miR-139 decreased the expression of IL-6 mRNA by 38% and of secreted IL-6 protein by 40%. However, overexpression of miR-139 increased the expression of IL-6 mRNA by 36% and of secreted IL-6 protein by 56%. These data correlated with altered expression profile of MCPIP1 in transfected chondrocytes. Studies with a luciferase reporter construct confirmed the interactions of miR-139 with the 'seed sequence' located in the 3' UTR of MCPIP mRNA. Furthermore, miR-139 overexpression increased the catabolic gene expression but expression of anabolic markers remained unchanged. Overexpression of miR-139 also induced apoptosis in OA chondrocytes. Importantly, we also discovered that IL-6 is a potent inducer of miR-139 expression in OA chondrocytes. These findings indicate that miR-139 functions as a post-transcriptional regulator of MCPIP1 expression and enhances IL-6 expression, which further upregulates miR-139 expression in OA chondrocytes. These results support our hypothesis that miR-139-mediated downregulation of MCPIP1 promotes IL-6 expression in OA. Therefore, targeting miR-139 could be therapeutically beneficial in the management of OA.
Subject(s)
Aged , Female , Humans , Male , Middle Aged , 3' Untranslated Regions , Apoptosis , Chondrocytes/metabolism , Down-Regulation , Gene Expression Regulation , Interleukin-6/genetics , MicroRNAs/genetics , Osteoarthritis/genetics , RNA, Messenger/genetics , Ribonucleases/genetics , Transcription Factors/genetics , Up-RegulationABSTRACT
A model for random molecular evolution based on recurrent mutation is proposed. Recurrent mutation replaces completely any original base in a nucleotidic site. This occurs if more than four times the number of reproductive cycles equal to the reciprocal of the mutation rate happen; no matter the population size, the number of nucleotides a genome has, or the taxa at which it belongs. The main results are: i) the expected distribution of DNA bases in a site is an isotetranomial distribution, where Adenine (A), Guanine (G), Cytosine (C) and Thymine (T) occur with probability equal to 0.25; ii) the distribution of bases in a site is independent from the distribution of bases in other sites. Several expected consequences that can be contrasted with actual data are generated. Species or operational taxonomic units (OTUs) that evolved in big populations should present distances equal to zero and similarities equal to one. OTUs evolving in small populations should present distances equal to 3/4 and similarities equal to 1/4. Thus, random molecular evolution by recurrent mutation cannot yield a tree at all. The only possible tree is that produced by random fluctuations of distances according to their variances (stochastic tree). Some consequences of the model on the expected primary structure of proteins are also analyzed. There are sufficient generations for any DNA segment evolving apart during the last four hundred million years, to reach those expected base distributions
Subject(s)
Chymotrypsinogen/genetics , Cytochromes c/genetics , Evolution, Molecular , Mutation/genetics , Phylogeny , Proinsulin/genetics , Ribonucleases/geneticsABSTRACT
En los últimos 5 años, las investigaciones en biología molecular han proporcionado información en el conocimiento del cáncer de colon, con sus consecuentes implicaciones clínicas. La base central de este conocimiento es la identificación y secuenciación del gen APC en el brazo largo del cromosoma 5. Alteraciones estructurales de este gen se han identificaco en los pacientes con poliposis adenomatosa familiar (PAF) y, en el síndrome de Gardner, lo cual sugiere que se trata de una misma enfermedad. Alteraciones estructurales y/o funcionales del gen APC, a diferencia de las hereditarias, podrían también ser adquiridas y, por lo tanto la causa principal del cáncer de colon esporádico. La PAF es una de las pocas enfermedades hereditarias, en donde marcadores moleculares son de gran utilidad en el diagnóstico del padecimiento aún en etapas clínicas tempranas o asintomáticas. El análisis de estudios de unión, utilizando fragmentos polimórficos de ADN generados con enzimas de restricción (RFLPs) son de gran utilidad para proporcionar el consejo genético a las familias afectadas. El conocimiento de estos estudios oriente y define la conducta médica a seguir después de realizar un estudio clínico-molecular integral de la familia afectada. Un estudio molecular más directo y sofisticado, aunque más caro, en los pacientes con cáncer de colon es la identificación y secuenciación del gen APC. Con fines de diagnóstico e investigación y, con el objeto de crear un centro de referencia a nivel nacional de cáncer de colon hereditario, estamos realizando este tipo de estudios moleculares en el Departamento de Gastroenterología del INNSZ.