Retromer dysfunction in amyotrophic lateral sclerosis.

Retromer is a heteropentameric complex that plays a specialized role in endosomal protein sorting and trafficking. Here, we report a reduction in the retromer proteins-vacuolar protein sorting 35 (VPS35), VPS26A, and VPS29-in patients with amyotrophic lateral sclerosis (ALS) and in the ALS model provided by transgenic (Tg) mice expressing the mutant superoxide dismutase-1 G93A. These changes are accompanied by a reduction of levels of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit GluA1, a proxy of retromer function, in spinal cords from Tg SOD1G93A mice. Correction of the retromer deficit by a viral vector expressing VPS35 exacerbates the paralytic phenotype in Tg SOD1G93A mice. Conversely, lowering Vps35 levels in Tg SOD1G93A mice ameliorates the disease phenotype. In light of these findings, we propose that mild alterations in retromer inversely modulate neurodegeneration propensity in ALS.

Sumoylation regulates the assembly and activity of the SMN complex.

SMN is a ubiquitously expressed protein and is essential for life. SMN deficiency causes the neurodegenerative disease spinal muscular atrophy (SMA), the leading genetic cause of infant mortality. SMN interacts with itself and other proteins to form a complex that functions in the assembly of ribonucleoproteins. SMN is modified by SUMO (Small Ubiquitin-like Modifier), but whether sumoylation is required for the functions of SMN that are relevant to SMA pathogenesis is not known. Here, we show that inactivation of a SUMO-interacting motif (SIM) alters SMN sub-cellular distribution, the integrity of its complex, and its function in small nuclear ribonucleoproteins biogenesis. Expression of a SIM-inactivated mutant of SMN in a mouse model of SMA slightly extends survival rate with limited and transient correction of motor deficits. Remarkably, although SIM-inactivated SMN attenuates motor neuron loss and improves neuromuscular junction synapses, it fails to prevent the loss of sensory-motor synapses. These findings suggest that sumoylation is important for proper assembly and function of the SMN complex and that loss of this post-translational modification impairs the ability of SMN to correct selective deficits in the sensory-motor circuit of SMA mice.

Exposure to NO2, CO, and PM2.5 is linked to regional DNA methylation differences in asthma.

Background: DNA methylation of CpG sites on genetic loci has been linked to increased risk of asthma in children exposed to elevated ambient air pollutants (AAPs). Further identification of specific CpG sites and the pollutants that are associated with methylation of these CpG sites in immune cells could impact our understanding of asthma pathophysiology. In this study, we sought to identify some CpG sites in specific genes that could be associated with asthma regulation (Foxp3 and IL10) and to identify the different AAPs for which exposure prior to the blood draw is linked to methylation levels at these sites. We recruited subjects from Fresno, California, an area known for high levels of AAPs. Blood samples and responses to questionnaires were obtained (n = 188), and in a subset of subjects (n = 33), repeat samples were collected 2 years later. Average measures of AAPs were obtained for 1, 15, 30, 90, 180, and 365 days prior to each blood draw to estimate the short-term vs. long-term effects of the AAP exposures. Results: Asthma was significantly associated with higher differentially methylated regions (DMRs) of the Foxp3 promoter region (p = 0.030) and the IL10 intronic region (p = 0.026). Additionally, at the 90-day time period (90 days prior to the blood draw), Foxp3 methylation was positively associated with NO2, CO, and PM2.5 exposures (p = 0.001, p = 0.001, and p = 0.012, respectively). In the subset of subjects retested 2 years later (n = 33), a positive association between AAP exposure and methylation was sustained. There was also a negative correlation between the average Foxp3 methylation of the promoter region and activated Treg levels (p = 0.039) and a positive correlation between the average IL10 methylation of region 3 of intron 4 and IL10 cytokine expression (p = 0.030). Conclusions: Short-term and long-term exposures to high levels of CO, NO2, and PM2.5 were associated with alterations in differentially methylated regions of Foxp3. IL10 methylation showed a similar trend. For any given individual, these changes tend to be sustained over time. In addition, asthma was associated with higher differentially methylated regions of Foxp3 and IL10.

Physical activity, black carbon exposure, and DNA methylation in the FOXP3 promoter.

BACKGROUND: Physical activity is associated with improvement in lung function; however, pollution exposure during physical activity can lead to a transient reduction in lung function. This paradoxical relationship may be linked to altered T regulatory (Treg) cell activity, which increases with exercise and suppresses airway inflammation, but decreases in association with exposure to air pollution. To clarify these relationships, we investigated buccal cell DNA methylation of the forkhead box p3 (FOXP3) gene promoter, a proposed biomarker of Treg activity. We hypothesized that active urban children would have lower FOXP3 promoter methylation, associated with better lung function compared to non-active children. We also hypothesized that this relationship would be attenuated by high exposure to the air pollutant black carbon (BC). METHODS: We performed a cross-sectional study of 135 children ages 9-14 who live in New York City. Activity was measured across 6 days. BC exposure was assessed by personal monitors worn for two 24-h periods, followed by lung function assessment. Buccal swabs were collected for DNA methylation analysis of three regions (six CpG sites) in the FOXP3 promoter. RESULTS: In multivariable regression models, overall, there was no significant relationship between physical activity and FOXP3 promoter methylation (p > 0.05). However, in stratified analyses, among children with higher BC exposure (≥1200 ng/m3), physical activity was associated with 2.37% lower methylation in promoter 2 (CpGs -77, -65, and -58) (ßestimate = -2.37%, p < 0.01) but not among those with lower BC exposure (ßestimate = 0.54%, p > 0.05). Differences across strata were statistically significant (pinteraction = 0.04). Among all children, after controlling for BC concentration, promoter 2 methylation was associated with reduced FEV1/FVC (ßestimate = -0.40%, p < 0.01) and reduced FEF25-75% (ßestimate = -1.46%, p < 0.01). CONCLUSIONS: Physical activity in urban children appeared associated with lower FOXP3 promoter methylation, a possible indicator of greater Treg function, under conditions of high BC exposure. Reduced FOXP3 promoter methylation was associated with higher lung function. These findings suggest that physical activity may induce immunologic benefits, particularly for urban children with greater risk of impaired lung function due to exposure to higher air pollution. FOXP3 promoter buccal cell methylation may function as a useful biomarker of that benefit.

Reduced mouse allergen is associated with epigenetic changes in regulatory genes, but not mouse sensitization, in asthmatic children.

Chronic exposure to mouse allergen may contribute greatly to the inner-city asthma burden. We hypothesized that reducing mouse allergen exposure may modulate the immunopathology underlying symptomatic pediatric allergic asthma, and that this occurs through epigenetic regulation. To test this hypothesis, we studied a cohort of mouse sensitized, persistent asthmatic inner-city children undergoing mouse allergen-targeted integrated pest management (IPM) vs education in a randomized controlled intervention trial. We found that decreasing mouse allergen exposure, but not cockroach, was associated with reduced FOXP3 buccal DNA promoter methylation, but this was unrelated to mouse specific IgE production. This finding suggests that the environmental epigenetic regulation of an immunomodulatory gene may occur following changing allergen exposures in some highly exposed cohorts. Given the clinical and public health importance of inner-city pediatric asthma and the potential impact of environmental interventions, further studies will be needed to corroborate changes in epigenetic regulation following changing exposures over time, and determine their impact on asthma morbidity in susceptible children.

Epigenetic regulation: the interface between prenatal and early-life exposure and asthma susceptibility.

Asthma is a complex disease with genetic and environmental influences and emerging evidence suggests that epigenetic regulation is also a major contributor. Here, we focus on the developing paradigm that epigenetic dysregulation in asthma and allergy may start as early as in utero following several environmental exposures. We summarize the pathways important to the allergic immune response that are epigenetically regulated, the key environmental exposures associated with epigenetic changes in asthma genes, and newly identified epigenetic biomarkers that have been linked to clinical asthma. We conclude with a brief discussion about the potential to apply newly developing technologies in epigenetics to the diagnosis and treatment of asthma and allergy. The inherent plasticity of epigenetic regulation following environmental exposures offers opportunities for prevention using environmental remediation, measuring novel biomarkers for early identification of those at risk, and applying advances in pharmaco-epigenetics to tailor medical therapies that maximize efficacy of treatment. 'Precision Medicine' in asthma and allergy is arriving. As the field advances this may involve an individually tailored approach to the prevention, early detection, and treatment of disease based on the knowledge of an individual's epigenetic profile.

Detection methods for microRNAs in clinic practice.

MicroRNAs (miRNA) are short non-coding RNA molecules that regulate gene expression. miRNAs profiles are specific for cell lineages and tissues, and their changes reflect pathological processes. This fact introduces the possibility of their use in diagnostics. The application of miRNAs in diagnostics is critically dependent on the establishment of miRNA profiles that can discriminate patients from normal healthy individuals with good sensitivity and specificity and on the development of methods for their accurate and high-throughput quantification. In this review, we present an overview of some of the different techniques and methods currently used to detect miRNAs. We focus on methods that can be employed in routine clinic diagnostics indicating their advantages as well as their shortcomings, with special attention being paid to the most innovative ones. Since disease-specific miRNAs can be found in blood serum, we also present emerging methods for the detection of circulating miRNAs as a way of fast, reliable and non-invasive diagnostic.

Analytical aspects of microRNA in diagnostics: a review.

MicroRNAs (miRNA) are short (∼22 nucleotides) non-coding RNA molecules that regulate gene expression at the post-transcriptional level. Their expression is specific to cells and tissues and is temporally regulated. miRNAs are known to be involved in developmental and physiological processes, and their dysregulation leads to development of diseases. Since their profiles reflect pathological processes, miRNAs have recently been proposed as being useful in diagnostics as biomarkers of the onset, prognosis and risk of diseases, as well as in the classification of different types of cancer. The establishment of miRNA profiles that are representative of diseases and the detection of different types and levels of miRNA in samples are therefore critical milestones in diagnostics. miRNAs can be detected in blood and body fluids as well as in tissues, thus making non-invasive collection of samples possible. For a method to be useful in diagnostics, it should be simple, inexpensive and highly sensitive. Here, we will review current methods of detecting miRNAs and indicate the advantages and disadvantages of each techniques. We will then summarize some of the clinical evidence for the potential application of miRNAs as biomarkers in diagnostics. We conclude providing some general perspectives on the use of miRNAs in clinical situations, including therapeutic applications.

Rapid in situ codetection of noncoding RNAs and proteins in cells and formalin-fixed paraffin-embedded tissue sections without protease treatment.

Noncoding RNAs (ncRNAs) comprise a diverse group of RNAs that function in essential cellular processes such as pre-mRNA splicing and mRNA translation and also regulate various aspects of gene expression in physiology and development. Methods of subcellular and tissue localization of ncRNAs are essential to understand their biological roles and their contribution to disease. We describe a rapid fluorescent (FISH) or chromogenic (CISH) in situ hybridization protocol for localization of ncRNAs (including microRNAs (miRNAs), small nucleolar RNAs (snoRNAs), small nuclear RNAs (snRNAs), piwi-associated RNAs (piRNAs) and ribosomal RNAs (rRNAs)) in formalin-fixed, paraffin-embedded (FFPE) tissues and cultured cells, using locked nucleic acid (LNA)-modified oligonucleotides. In this protocol, sections are heated in citrate buffer, which eliminates the need for protease treatment, thus preserving optimal morphology and protein epitopes, and allowing the simultaneous detection of proteins with immunofluorescence staining (IF). LNA-FISH requires 5 h, or between 10 and 36 h when combined with IF; LNA-CISH requires 2 d.

Arginine methylation of Piwi proteins catalysed by dPRMT5 is required for Ago3 and Aub stability.

Piwi family proteins are essential for germline development and bind piwi-interacting RNAs (piRNAs). The grandchildless gene aub of Drosophila melanogaster encodes the piRNA-binding protein Aubergine (Aub), which is essential for formation of primordial germ cells (PGCs). Here we report that Piwi family proteins of mouse, Xenopus laevis and Drosophila contain symmetrical dimethylarginines (sDMAs). We found that Piwi proteins are expressed in Xenopus oocytes and we identified numerous Xenopus piRNAs. We report that the Drosophila homologue of protein methyltransferase 5 (dPRMT5, csul/dart5), which is also the product of a grandchildless gene, is required for arginine methylation of Drosophila Piwi, Ago3 and Aub proteins in vivo. Loss of dPRMT5 activity led to a reduction in the levels of piRNAs, Ago3 and Aub proteins, and accumulation of retrotransposons in the Drosophila ovary. Our studies explain the relationship between aub and dPRMT5 (csul/dart5) genes by demonstrating that dPRMT5 is the enzyme that methylates Aub. Our findings underscore the significance of sDMA modification of Piwi proteins in the germline and suggest an interacting pathway of genes that are required for piRNA function and PGC specification.

Biochemical and genetic evidence for a role of IGHMBP2 in the translational machinery.

The human motor neuron degenerative disease spinal muscular atrophy with respiratory distress type 1 (SMARD1) is caused by loss of function mutations of immunoglobulin mu-binding protein 2 (IGHMBP2), a protein of unknown function that contains DNA/RNA helicase and nucleic acid-binding domains. Reduced IGHMBP2 protein levels in neuromuscular degeneration (nmd) mice, the mouse model of SMARD1, lead to motor neuron degeneration. We report the biochemical characterization of IGHMBP2 and the isolation of a modifier locus that rescues the phenotype and motor neuron degeneration of nmd mice. We find that a 166 kb BAC transgene derived from CAST/EiJ mice and containing tRNA genes and activator of basal transcription 1 (Abt1), a protein-coding gene that is required for ribosome biogenesis, contains the genetic modifier responsible for motor neuron rescue. Our biochemical investigations show that IGHMBP2 associates physically with tRNAs and in particular with tRNA(Tyr), which are present in the modifier and with the ABT1 protein. We find that transcription factor IIIC-220 kDa (TFIIIC220), an essential factor required for tRNA transcription, and the helicases Reptin and Pontin, which function in transcription and in ribosome biogenesis, are also part of IGHMBP2-containing complexes. Our findings strongly suggest that IGHMBP2 is a component of the translational machinery and that these components can be manipulated genetically to suppress motor neuron degeneration.

A novel monoclonal antibody against human Argonaute proteins reveals unexpected characteristics of miRNAs in human blood cells.

Argonaute (Ago) proteins bind to microRNA (miRNAs) and short interfering RNAs (siRNAs) and form the core components of effector complexes that mediate miRNA and siRNA function. Currently, there is a paucity of reliable antibodies against mammalian Ago proteins, thus precluding studies of endogenous Ago proteins from tissues. Here we report the development of 2A8, a novel anti-Ago monoclonal antibody that recognizes human and mouse Ago proteins and efficiently immunoprecipitates miRNAs. We report the characterization of 2A8 and its use to clone miRNAs from human brain and from preparations of human polymorphonuclear leukocytes (neutrophils), which revealed a prevalent miRNA with unusual features.

An mRNA m7G cap binding-like motif within human Ago2 represses translation.

microRNAs (miRNAs) bind to Argonaute (Ago) proteins and inhibit translation or promote degradation of mRNA targets. Human let-7 miRNA inhibits translation initiation of mRNA targets in an m(7)G cap-dependent manner and also appears to block protein production, but the molecular mechanism(s) involved is unknown and the role of Ago proteins in translational regulation remains elusive. Here we identify a motif (MC) within the Mid domain of Ago proteins, which bears significant similarity to the m(7)G cap-binding domain of eIF4E, an essential translation initiation factor. We identify conserved aromatic residues within the MC motif of human Ago2 that are required for binding to the m(7)G cap and for translational repression but do not affect the assembly of Ago2 with miRNA or its catalytic activity. We propose that Ago2 represses the initiation of mRNA translation by binding to the m(7)G cap of mRNA targets, thus likely precluding the recruitment of eIF4E.