RNAi and microRNAs: from animal models to disease therapy

The discovery of the phenomenon of RNA interference (RNAi) and its existence in mammals quickly suggested a great potential for use in disease therapy. Rapid advances have been made in the development of RNAi-based technologies and promising results have been obtained from studies on mammalian cell culture systems and animal in vivo models. However, the progress in our understanding of the RNAi pathway and the related function of microRNAs (miRNAs) have also raised concerns regarding various types of side effects that may restrict the use of this technology in human therapy. At the same time, our new knowledge about the functional roles of miRNAs as regulators of many cellular processes, including proliferation, differentiation, development, and neuronal function, is revolutionizing cell biology and will have a major impact on medical research. In this review, we focus on the discoveries that have been made in animal models and how this insight can be translated to human medicine and disease therapy. In this connection, we will particularly discuss the challenges associated with the efforts to develop RNAi-based therapeutics.     

Reply to Horizons Article 'Some ideas about the role of lipids in the life cycle of Calanus finmarchicus' Irigoien (2004): II

Recently, Irigoien (Irigoien, 2004) suggested a conceptual modelof the role of lipids in the life cycle of the marine copepodCalanus finmarchicus. As he pointed out, lipids accumulatedbefore     

Improved v[combining dot above]o2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist

ABSTRACT: St?ren, ?, Bratland-Sanda, S, Haave, M, and Helgerud, J. Improved V[Combining Dot Above]O2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist. J Strength Cond Res 26(10): 2705-2711, 2012-The present study investigated to what extent more high aerobic intensity interval training (HAIT) and reduced training volume would influence maximal oxygen uptake (V[Combining Dot Above]O2max) and time trial (TT) performance in an elite national cyclist in the preseason period. The cyclist was tested for V[Combining Dot Above]O2max, cycling economy (Cc), and TT performance on an ergometer cycle during 1 year. Training was continuously logged using heart rate monitor during the entire period. Total monthly training volume was reduced in the 2011 preseason compared with the 2010 preseason, and 2 HAIT blocks (14 sessions in 9 days and 15 sessions in 10 days) were performed as running. Between the HAIT blocks, 3 HAIT sessions per week were performed as cycling. From November 2010 to February 2011, the cyclist reduced total average monthly training volume by 18% and cycling training volume by 60%. The amount of training at 90-95% HRpeak increased by 41%. V[Combining Dot Above]O2max increased by 10.3% on ergometer cycle. TT performance improved by 14.9%. Cc did not change. In conclusion, preseason reduced total training volume but increased amount of HAIT improved V[Combining Dot Above]O2max and TT performance without any changes in Cc. These improvements on cycling appeared despite that the HAIT blocks were performed as running. Reduced training time, and training transfer from running into improved cycling form, may be beneficial for cyclists living in cold climate areas.     

Galerina Earle: A polyphyletic genus in the consortium of dark-spored agarics

The basidiomycete genus Galerina Earle accommodates more than 300 small brown-spored agarics worldwide, predominantly described from the Northern hemisphere. The delimitation of species and infrageneric units hitherto has been based on morphological and, to some extent, ecological characters. In this study we have analyzed nuclear ribosomal LSU and ITS sequences to reveal infrageneric phylogeny and the phylogenetic placement of Galerina among the dark-spored agarics. Sequences from 36 northern hemisphere Galerina species and 19 other dark-spored taxa were analyzed, some of them obtained from EMBL/GenBank. Our results, received from Bayesian and distance methods, strongly suggest that Galerina is a polyphyletic genus. The LSU analysis shows that Galerina is composed of three or four separate monophyletic main groups. In addition, a few species cluster together with other dark-spored agarics. The same groups are recognized in the ITS tree and they correspond roughly to previously recognized subgenera or sections in Galerina. With high support our LSU analysis suggests that Gymnopilus is a monophyletic genus and that Gymnopilus and one of the Galerina lineages ("mycenopsis") are sister groups. The analyses further indicate that the Galerina lineages, as well as the genus Gymnopilus, could be referred to a strongly emendated family Strophariaceae, which corresponds largely to the family as circumscribed by Kühner (1980). Our results affirm that morphological characters often are highly homoplastic in the agarics. At the present stage formal taxonomic consequences or nomenclatural changes are not proposed.     

Refining the rules of gliadin T cell epitope binding to the disease-associated DQ2 molecule in celiac disease: importance of proline spacing and glutamine deamidation

Celiac disease is driven by intestinal T cells responsive to proline-rich gluten peptides that often harbor glutamate residues formed by tissue transglutaminase-mediated glutamine conversion. The disease is strongly associated with the HLA variant DQ2.5 (DQA1*05, DQB1*02), and intestinal gluten-reactive T cells from DQ2.5-positive patients are uniquely restricted by this HLA molecule. In this study, we describe the mapping of two novel T cell epitopes of gamma-gliadin and the experimental identification of the DQ2.5 binding register of these and three other gamma-gliadin epitopes. The new data extend the knowledge base for understanding the binding of gluten peptides to DQ2.5. The alignment of the experimentally determined binding registers of nine gluten epitopes reveal positioning of proline residues in positions P1, P3, P6, and P8 but never in positions P2, P4, P7, and P9. Glutamate residues formed by tissue transglutaminase-mediated deamidation are found in position P1, P4, P6, P7, or P9, but only deamidations in positions P4 and P6, and rarely in P7, seem to be crucial for T cell recognition. The majority of these nine epitopes are recognized by celiac lesion T cells when presented by the related but nonassociated DQ2.2 (DQA1*0201, DQB1*02) molecule. Interestingly, the DQ2.2 presentation for most epitopes is less efficient than presentation by the DQ2.5 molecule, and this is particularly prominent for the alpha-gliadin epitopes. Contrary to previous findings, our data do not show selective presentation of DQ2.5 over DQ2.2 for gluten epitopes that carry proline residues at the P3 position.     

Coreceptor signal strength regulates positive selection but does not determine CD4/CD8 lineage choice in a physiologic in vivo model

TCR signals drive thymocyte development, but it remains controversial what impact, if any, the intensity of those signals have on T cell differentiation in the thymus. In this study, we assess the impact of CD8 coreceptor signal strength on positive selection and CD4/CD8 lineage choice using novel gene knockin mice in which the endogenous CD8alpha gene has been re-engineered to encode the stronger signaling cytoplasmic tail of CD4, with the re-engineered CD8alpha gene referred to as CD8.4. We found that stronger signaling CD8.4 coreceptors specifically improved the efficiency of CD8-dependent positive selection and quantitatively increased the number of MHC class I (MHC-I)-specific thymocytes signaled to differentiate into CD8+ T cells, even for thymocytes expressing a single, transgenic TCR. Importantly, however, stronger signaling CD8.4 coreceptors did not alter the CD8 lineage choice of any MHC-I-specific thymocytes, even MHC-I-specific thymocytes expressing the high-affinity F5 transgenic TCR. This study documents in a physiologic in vivo model that coreceptor signal strength alters TCR-signaling thresholds for positive selection and so is a major determinant of the CD4:CD8 ratio, but it does not influence CD4/CD8 lineage choice.     

The effect of exercise training on transverse tubules in normal, remodeled, and reverse remodeled hearts

The response of transverse (T)-tubules to exercise training in health and disease remains unclear. Therefore, we studied the effect of exercise training on the density and spacing of left ventricle cardiomyocyte T-tubules in normal and remodeled hearts that associate with detubulation, by confocal laser scanning microscopy. First, exercise training in normal rats increased cardiomyocyte volume by 16% (P < 0.01), with preserved T-tubule density. Thus, the T-tubules adapted to the physiologic hypertrophy. Next, we studied T-tubules in a rat model of metabolic syndrome with pressure overload-induced concentric left ventricle hypertrophy, evidenced by 15% (P < 0.01) increased cardiomyocyte size. These rats had only 85% (P < 0.01) of the T-tubule density of control rats. Exercise training further increased cardiomyocyte volume by 8% (P < 0.01); half to that in control rats, but the T-tubule density remained unchanged. Finally, post-myocardial infarction heart failure induced severe cardiac pathology, with a 70% (P < 0.01) increased cardiomyocyte volume that included both eccentric and concentric hypertrophy and 55% (P < 0.01) reduced T-tubule density. Exercise training reversed 50% (P < 0.01) of the pathologic hypertrophy, whereas the T-tubule density increased by 40% (P < 0.05) compared to sedentary heart failure, but remained at 60% of normal hearts (P < 0.01). Physiologic hypertrophy associated with conserved T-tubule spacing (~1.8-1.9 μm), whereas in pathologic hypertrophy, T-tubules appeared disorganized without regular spacing. In conclusion, cardiomyocytes maintain the relative T-tubule density during physiologic hypertrophy and after mild concentric pathologic hypertrophy, whereas after severe pathologic remodeling with a substantial loss of T-tubules; exercise training reverses the remodeling and partly corrects the T-tubule density.