Pms2 suppresses large expansions of the (GAA·TTC)n sequence in neuronal tissues

Copyright @ 2012 Bourn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Expanded trinucleotide repeat sequences are the cause of several inherited neurodegenerative diseases. Disease pathogenesis is correlated with several features of somatic instability of these sequences, including further large expansions in postmitotic tissues. The presence of somatic expansions in postmitotic tissues is consistent with DNA repair being a major determinant of somatic instability. Indeed, proteins in the mismatch repair (MMR) pathway are required for instability of the expanded (CAG·CTG)(n) sequence, likely via recognition of intrastrand hairpins by MutSβ. It is not clear if or how MMR would affect instability of disease-causing expanded trinucleotide repeat sequences that adopt secondary structures other than hairpins, such as the triplex/R-loop forming (GAA·TTC)(n) sequence that causes Friedreich ataxia. We analyzed somatic instability in transgenic mice that carry an expanded (GAA·TTC)(n) sequence in the context of the human FXN locus and lack the individual MMR proteins Msh2, Msh6 or Pms2. The absence of Msh2 or Msh6 resulted in a dramatic reduction in somatic mutations, indicating that mammalian MMR promotes instability of the (GAA·TTC)(n) sequence via MutSα. The absence of Pms2 resulted in increased accumulation of large expansions in the nervous system (cerebellum, cerebrum, and dorsal root ganglia) but not in non-neuronal tissues (heart and kidney), without affecting the prevalence of contractions. Pms2 suppressed large expansions specifically in tissues showing MutSα-dependent somatic instability, suggesting that they may act on the same lesion or structure associated with the expanded (GAA·TTC)(n) sequence. We conclude that Pms2 specifically suppresses large expansions of a pathogenic trinucleotide repeat sequence in neuronal tissues, possibly acting independently of the canonical MMR pathway.IDB was supported by a postdoctoral fellowship from the National Ataxia Foundation. RMP was supported by Ataxia UK. SA was supported by The Wellcome Trust. This research was made possible by grants from the National Institutes of Health (NIH/NINDS) and the Muscular Dystrophy Association to S.I.B

Epigenetic Silencing in Friedreich Ataxia Is Associated with Depletion of CTCF (CCCTC-Binding Factor) and Antisense Transcription

Background: Over 15 inherited diseases are caused by expansion of triplet-repeats. Friedreich ataxia (FRDA) patients are homozygous for an expanded GAA triplet-repeat sequence in intron 1 of the FXN gene. The expanded GAA triplet-repeat results in deficiency of FXN gene transcription, which is reversed via administration of histone deacetylase inhibitors indicating that transcriptional silencing is at least partially due to an epigenetic abnormality. Methodology/Principal Findings: We found a severe depletion of the chromatin insulator protein CTCF (CCCTC-binding factor) in the 59UTR of the FXN gene in FRDA, and coincident heterochromatin formation involving the +1 nucleosome via enrichment of H3K9me3 and recruitment of heterochromatin protein 1. We identified FAST-1 (FXN Antisense Transcript – 1), a novel antisense transcript that overlaps the CTCF binding site in the 59UTR, which was expressed at higher levels in FRDA. The reciprocal relationship of deficient FXN transcript and higher levels of FAST-1 seen in FRDA was reproduced in normal cells via knockdown of CTCF. Conclusions/Significance: CTCF depletion constitutes an epigenetic switch that results in increased antisense transcription, heterochromatin formation and transcriptional deficiency in FRDA. These findings provide a mechanistic basis for the transcriptional silencing of the FXN gene in FRDA, and broaden our understanding of disease pathogenesis in triplet-repea

Somatic instability of the expanded GAA triplet-repeat sequence in Friedreich ataxia progresses throughout life

Friedreich ataxia (FRDA) patients are homozygous for expanded GAA triplet-repeat alleles in the FXN gene. Primary neurodegeneration involving the dorsal root ganglia (DRG) results in progressive ataxia. While it is known that DRG are inherently sensitive to frataxin deficiency, recent observations also indicate that they show age-dependent, further expansion of the GAA triplet-repeat mutation. Whether somatic instability is progressive has not been systematically investigated in FRDA patients. Small pool PCR analysis of ~2300 individual molecules from tissues of an 18-week fetus, homozygous for expanded alleles, revealed very low levels of instability compared with adult-derived tissues (4.2% versus 30.6%, P<0.0001). Mutation load in blood samples from multiple patients and carriers increased significantly with age, ranging from 7.5% at 18-weeks gestation to 78.7% at 49y (R=0.91; P=0.0001). Therefore, somatic instability in FRDA occurs mostly after early embryonic development and progresses throughout life, lending further support to the role of postnatal somatic instability in disease pathogenesis

Friedreich ataxia patient tissues exhibit increased 5-hydroxymethylcytosine modification and decreased CTCF binding at the FXN locus

© 2013 Al-Mahdawi et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use,distribution, and reproduction in any medium, provided the original author and source are credited.This article has been made available through the Brunel Open Access Publishing Fund.Friedreich ataxia (FRDA) is caused by a homozygous GAA repeat expansion mutation within intron 1 of the FXN gene, which induces epigenetic changes and FXN gene silencing. Bisulfite sequencing studies have identified 5-methylcytosine (5 mC) DNA methylation as one of the epigenetic changes that may be involved in this process. However, analysis of samples by bisulfite sequencing is a time-consuming procedure. In addition, it has recently been shown that 5-hydroxymethylcytosine (5 hmC) is also present in mammalian DNA, and bisulfite sequencing cannot distinguish between 5 hmC and 5 mC.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 242193/EFACTS (CS), the Wellcome Trust [089757] (SA) and Ataxia UK (RMP) to MAP

Paradoxical relationship between proton pump inhibitors and COVID-19: A systematic review and meta-analysis

BACKGROUND The proton pump inhibitors (PPIs), used to reduce gastric acid secretion, represent one of the most widely used pharmaceutical classes in the world. Their consumption as a risk factor for the evolution of severe forms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been investigated patients. These risks also appear to be linked to the duration and the dosage. On the other hand, several studies have emerged with regard to the protective or therapeutic effects of these drugs. More and more evidence underlines the immunomodulatory and anti-fibrotic role of PPIs. In addition, their ability to alkalize the contents of endosomes and lysosomes serves as an obstacle to the entry of the virus into the host cells.AIMTo identify studies on the relationship between the intake of PPIs and coronavirus disease 2019 (COVID-19) in patients affected by SARS-CoV-2 infection, with the main objective of evaluating the outcomes related to severity and mortality. METHODS A literature review was performed in November 2020. The MEDLINE/PubMed, Cochrane Library, EMBASE and Google Scholar databases were searched for all relevant articles published in English on this topic. The search terms were identified by means of controlled vocabularies, such as the National Library of Medicine’s MESH (Medical Subject Headings) and keywords. The MESH terms and keywords used were as follows: “COVID-19”, “proton pump inhibitors”, ”PPIs”, “SARS-CoV-2”, “outcomes”, “severity” and “mortality”. The inclusion criteria regarding the studies considered in our analysis were: meta-analysis, casecontrol, hospital-based case-control, population-based case-control, retrospective studies, online survey, as well as cohort-studies, while articles not published as full reports, such as conference abstracts, case reports and editorials were excluded. We tried to summarize and pool all the data if available. RESULTS A total of 9 studies were found that described the use of PPIs, of which only 5 clearly reported the severity and mortality data in SARS-CoV-2 patients. Our pooled incidence analysis of severe events did not differ between patients with and without PPIs (odds ratio 1.65, 95% confidence interval: 0.62-4.35) (P = 0.314), or for mortality (odds ratio 1.77, 95% confidence interval: 0.62-5.03) (P = 0.286). CONCLUSION Detailed and larger case studies are needed to accurately understand the role of PPIs in this viral infection

Replication in mammalian cells recapitulates the locus-specific differences in somatic instability of genomic GAA triplet-repeats

Friedreich ataxia is caused by an expanded (GAA·TTC)(n) sequence in intron 1 of the FXN gene. Small pool PCR analysis showed that pure (GAA·TTC)(44+) sequences at the FXN locus are unstable in somatic cells in vivo, displaying both expansions and contractions. On searching the entire human and mouse genomes we identified three other genomic loci with pure (GAA·TTC)(44+) sequences. Alleles at these loci showed mutation loads of <1% compared with 6.3–30% for FXN alleles of similar length, indicating that somatic instability in vivo is regulated by locus-specific factors. Since distance between the origin of replication and the (CTG·CAG)(n) sequence modulates repeat instability in mammalian cells, we tested if this could also recapitulate the locus-specific differences for genomic (GAA·TTC)(n) sequences. Repeat instability was evaluated following replication of a (GAA·TTC)(115) sequence in transfected COS1 cells under the control of the SV40 origin of replication located at one of five different distances from the repeat. Indeed, depending on the location of the SV40 origin relative to the (GAA·TTC)(n) sequence, we noted either no instability, predominant expansion or both expansion and contraction. These data suggest that mammalian DNA replication is a possible mechanism underlying locus-specific differences in instability of GAA triplet-repeat sequences

A mutation screening of oncogenes, tumor suppressor gene TP53 and nuclear encoded mitochondrial complex I genes in oncocytic thyroid tumors.

Background: Thyroid neoplasias with oncocytic features represent a specific phenotype in non-medullary thyroid cancer, reflecting the unique biological phenomenon of mitochondrial hyperplasia in the cytoplasm. Oncocytic thyroid cells are characterized by a prominent eosinophilia (or oxyphilia) caused by mitochondrial abundance. Although disruptive mutations in the mitochondrial DNA (mtDNA) are the most significant hallmark of such tumors, oncocytomas may be envisioned as heterogeneous neoplasms, characterized by multiple nuclear and mitochondrial gene lesions. We investigated the nuclear mutational profile of oncocytic tumors to pinpoint the mutations that may trigger the early oncogenic hit. Methods: Total DNA was extracted from paraffin-embedded tissues from 45 biopsies of oncocytic tumors. High-resolution melting was used for mutation screening of mitochondrial complex I subunits genes. Specific nuclear rearrangements were investigated by RT-PCR (RET/PTC) or on isolated nuclei by interphase FISH (PAX8/PPARγ). Recurrent point mutations were analyzed by direct sequencing. Results: In our oncocytic tumor samples, we identified rare TP53 mutations. The series of analyzed cases did not include poorly- or undifferentiated thyroid carcinomas, and none of the TP53 mutated cases had significant mitotic activity or high-grade features. Thus, the presence of disruptive TP53 mutations was completely unexpected. In addition, novel mutations in nuclear-encoded complex I genes were identified. Conclusions: These findings suggest that nuclear genetic lesions altering the bioenergetics competence of thyroid cells may give rise to an aberrant mitochondria-centered compensatory mechanism and ultimately to the oncocytic phenotype. Keywords: Oncocytic carcinoma, Nuclear mitochondrial complex I subunits, Oncogene mutation analysi

MutLα heterodimers modify the molecular phenotype of Friedreich ataxia

This article has been made available through the Brunel Open Access Publishing Fund.Background: Friedreich ataxia (FRDA), the most common autosomal recessive ataxia disorder, is caused by a dynamic GAA repeat expansion mutation within intron 1 of FXN gene, resulting in down-regulation of frataxin expression. Studies of cell and mouse models have revealed a role for the mismatch repair (MMR) MutS-heterodimer complexes and the PMS2 component of the MutLα complex in the dynamics of intergenerational and somatic GAA repeat expansions: MSH2, MSH3 and MSH6 promote GAA repeat expansions, while PMS2 inhibits GAA repeat expansions. Methodology/Principal Findings: To determine the potential role of the other component of the MutLα complex, MLH1, in GAA repeat instability in FRDA, we have analyzed intergenerational and somatic GAA repeat expansions from FXN transgenic mice that have been crossed with Mlh1 deficient mice. We find that loss of Mlh1 activity reduces both intergenerational and somatic GAA repeat expansions. However, we also find that loss of either Mlh1 or Pms2 reduces FXN transcription, suggesting different mechanisms of action for Mlh1 and Pms2 on GAA repeat expansion dynamics and regulation of FXN transcription. Conclusions/Significance: Both MutLα components, PMS2 and MLH1, have now been shown to modify the molecular phenotype of FRDA. We propose that upregulation of MLH1 or PMS2 could be potential FRDA therapeutic approaches to increase FXN transcription. © 2014 Ezzatizadeh et al.This article has been made available through the Brunel Open Access Publishing Fund

Redescription of three little known genera of Acanthosomatidae (Hemiptera: Pentatomoidea) from South America

Se analizan los ejemplares tipo de géneros monotípicos y poco conocidos de Acanthosomatidae, Cochabambia Pirán (Ditomotarsinae) y Tunaria Pirán (Blaudusinae: Blaudusini) de Bolivia. Se redescriben en base a caracteres conocidos y nuevos y se discute su posición taxonómica. Tunaria es considerado sinónimo menor de Blaudus Stål, resultando la nueva combinación Blaudus andicola (Pirán) comb. nov. Por otra parte se describe por primera vez al macho de Pseudosinopla canaliculus (Reed, 1898) (Blaudusinae: Blaudusini).The type specimens of two monotypic and little-known genera of Acanthosomatidae from Bolivia, Cochabambia Pirán (Ditomotarsinae) and Tunaria Pirán (Blaudusinae: Blaudusini) are examined. Both species are described using known and new characters, and their taxonomic position is discussed. Tunaria is considered a junior synonym of Blaudus Stål. Consequently, Blaudus andicola (Pirán) comb. nov. is proposed as a new combination. On the other hand, the male of Pseudosinopla canaliculus (Reed, 1898) (Blaudusinae: Blaudusini) is described for the first time.Fil: Carpintero, Diego Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Carvajal, Mariom A.. Universidad de Magallanes; ChileFil: Faúndez, Eduardo I.. Universidad de Magallanes; ChileFil: Rider, David A.. North Dakota State University; Estados UnidosFil: de Biase, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

White light thermoplasmonic activated gold nanorod arrays enable the photo-thermal disinfection of medical tools from bacterial contamination

The outspread of bacterial pathogens causing severe infections and spreading rapidly, especially among hospitalized patients, is worrying and represents a global public health issue. Current disinfection techniques are becoming insufficient to counteract the spread of these pathogens because they carry multiple antibiotic-resistance genes. For this reason, a constant need exists for new technological solutions that rely on physical methods rather than chemicals. Nanotechnology support provides novel and unexplored opportunities to boost groundbreaking, next-gen solutions. With the help of plasmonic-assisted nanomaterials, we present and discuss our findings in innovative bacterial disinfection techniques. Gold nanorods (AuNRs) immobilized on rigid substrates are utilized as efficient white light-to-heat transducers (thermoplasmonic effect) for photo-thermal (PT) disinfection. The resulting AuNRs array shows a high sensitivity change in refractive index and an extraordinary capability in converting white light to heat, producing a temperature change greater than 50 °C in a few minute interval illumination time. Results were validated using a theoretical approach based on a diffusive heat transfer model. Experiments performed with a strain of Escherichia coli as a model microorganism confirm the excellent capability of the AuNRs array to reduce the bacteria viability upon white light illumination. Conversely, the E. coli cells remain viable without white light illumination, which also confirms the lack of intrinsic toxicity of the AuNRs array. The PT transduction capability of the AuNRs array is utilized to produce white light heating of medical tools used during surgical treatments, generating a temperature increase that can be controlled and is suitable for disinfection. Our findings are pioneering a new opportunity for healthcare facilities since the reported methodology allows non-hazardous disinfection of medical devices by simply employing a conventional white light lamp