Structure and mechanism of the RNA dependent RNase Cas13a from Rhodobacter capsulatus

Cas13a are single-molecule effectors of the Class II, Type VI family of CRISPR-Cas systems that are part of the bacterial and archaeal defense systems. These RNA-guided and RNA-activated RNA endonucleases are characterized by their ability to cleave target RNAs complementary to the crRNA-spacer sequence, as well as bystander RNAs in a sequence-unspecific manner. Due to cleavage of cellular transcripts they induce dormancy in the host cell and thus protect the bacterial population by aborting the infectious cycle of RNA-phages. Here we report the structural and functional characterization of a Cas13a enzyme from the photo-auxotrophic purple bacteria Rhodobacter capsulatus. The X-ray crystal structure of the RcCas13a-crRNA complex reveals its distinct crRNA recognition mode as well as the enzyme in its contracted, pre-activation conformation. Using site-directed mutagenesis in combination with mass spectrometry, we identified key residues responsible for pre-crRNA processing by RcCas13a in its distinct catalytic site, and elucidated the acid-base mediated cleavage reaction mechanism. In addition, RcCas13a cleaves target-RNA as well as bystander-RNAs in Escherichia coli which requires its catalytic active HEPN (higher eukaryotes and prokaryotes nucleotide binding) domain nuclease activity. Our data provide further insights into the molecular mechanisms and function of this intriguing family of RNA-dependent RNA endonucleases that are already employed as efficient tools for RNA detection and regulation of gene expression

Cardiac magnetic resonance imaging for preprocedural planning of percutaneous left atrial appendage closure

IntroductionPercutaneous closure of the left atrial appendage (LAA) facilitates stroke prevention in patients with atrial fibrillation. Optimal device selection and positioning are often challenging due to highly variable LAA shape and dimension and thus require accurate assessment of the respective anatomy. Transesophageal echocardiography (TEE) and x-ray fluoroscopy (XR) represent the gold standard imaging techniques. However, device underestimation has frequently been observed. Assessment based on 3-dimensional computer tomography (CTA) has been reported as more accurate but increases radiation and contrast agent burden. In this study, the use of non-contrast-enhanced cardiac magnetic resonance imaging (CMR) to support preprocedural planning for LAA closure (LAAc) was investigated.MethodsCMR was performed in thirteen patients prior to LAAc. Based on the 3-dimensional CMR image data, the dimensions of the LAA were quantified and optimal C-arm angulations were determined and compared to periprocedural data. Quantitative figures used for evaluation of the technique comprised the maximum diameter, the diameter derived from perimeter and the area of the landing zone of the LAA.ResultsPerimeter- and area-based diameters derived from preprocedural CMR showed excellent congruency compared to those measured periprocedurally by XR, whereas the respective maximum diameter resulted in significant overestimation (p < 0.05). Compared to TEE assessment, CMR-derived diameters resulted in significantly larger dimensions (p < 0.05). The deviation of the maximum diameter to the diameters measured by XR and TEE correlated well with the ovality of the LAA. C-arm angulations used during the procedures were in agreement with those determined by CMR in case of circular LAA.DiscussionThis small pilot study demonstrates the potential of non-contrast-enhanced CMR to support preprocedural planning of LAAc. Diameter measurements based on LAA area and perimeter correlated well with the actual device selection parameters. CMR-derived determination of landing zones facilitated accurate C-arm angulation for optimal device positioning

Phagocytosis and digestion of pH-sensitive fluorescent dye (Eos-FP) transfected E. coli in whole blood assays from patients with severe sepsis and septic shock

The function of phagocytic and antigen presenting cells is of crucial importance to sustain immune competence against infectious agents as well as malignancies. We here describe a reproducible procedure for the quantification of phagocytosis by leukocytes in whole blood. For this, a pH-sensitive green-fluorescent protein- (GFP) like dye (Eos-FP) is transfected into infectious microroganisms. After UV-irradiation, the transfected bacteria emit green (≈5160 nm) and red (≈581 nm) fluorescent light at 490 nm excitation. Since the red fluorescent light is sensitive to acidic pH, the phagocytosed bacteria stop emitting red fluorescent light as soon as the phagosomes fuse with lysosomes. The green fluorescence is maintained in the phagolysosome until pathogen degradation is completed. Fluorescence emission can be followed by flow cytometry with filter settings documenting fluorescence 1 (FL 1, FITC) and fluorescence 2 (FL 2, phycoerythrin, PE). Eos-FP transfected bacteria can also be traced within phagocytes using microscopical techniques. A standardized assay has been developed which is suitable for clinical studies by providing clinicians with syringes pre-filled with fixed and appropriately UV-irradiated Eos-FP E. coli (TruCulture™). After adding blood or body fluids to these containers and starting the incubation at 37°C, phagocytosis by granulocytes proceeds over time. Cultures can be terminated at a given time by lysing red blood cells followed by flow cytometry. A pilot study demonstrated that Eos-FP E. coli phagocytosis and digestion was up-regulated in the majority of patients with either severe sepsis or septic shock as compared to healthy donors (p < 0.0001 after o/n incubation). Following treatment with recombinant human granulocyte colony-stimulating factor (rhG-CSF) in selected patients with sepsis, phagolysosome fusion appeared to be accelerated

Progranulin Gene Variability and Plasma Levels in Bipolar Disorder and Schizophrenia

Basing on the assumption that frontotemporal lobar degeneration (FTLD), schizophrenia and bipolar disorder (BPD) might share common aetiological mechanisms, we analyzed genetic variation in the FTLD risk gene progranulin (GRN) in a German population of patients with schizophrenia (n = 271) or BPD (n = 237) as compared with 574 age-, gender- and ethnicity-matched controls. Furthermore, we measured plasma progranulin levels in 26 German BPD patients as well as in 61 Italian BPD patients and 29 matched controls

The effects of improving sleep on mental health (OASIS): a randomised controlled trial with mediation analysis

BACKGROUND: Sleep difficulties might be a contributory causal factor in the occurrence of mental health problems. If this is true, improving sleep should benefit psychological health. We aimed to determine whether treating insomnia leads to a reduction in paranoia and hallucinations. METHODS: We did this single-blind, randomised controlled trial (OASIS) at 26 UK universities. University students with insomnia were randomly assigned (1:1) with simple randomisation to receive digital cognitive behavioural therapy (CBT) for insomnia or usual care, and the research team were masked to the treatment. Online assessments took place at weeks 0, 3, 10 (end of therapy), and 22. The primary outcome measures were for insomnia, paranoia, and hallucinatory experiences. We did intention-to-treat analyses. The trial is registered with the ISRCTN registry, number ISRCTN61272251. FINDINGS: Between March 5, 2015, and Feb 17, 2016, we randomly assigned 3755 participants to receive digital CBT for insomnia (n=1891) or usual practice (n=1864). Compared with usual practice, the sleep intervention at 10 weeks reduced insomnia (adjusted difference 4·78, 95% CI 4·29 to 5·26, Cohen's d=1·11; p<0·0001), paranoia (-2·22, -2·98 to -1·45, Cohen's d=0·19; p<0·0001), and hallucinations (-1·58, -1·98 to -1·18, Cohen's d=0·24; p<0·0001). Insomnia was a mediator of change in paranoia and hallucinations. No adverse events were reported. INTERPRETATION: To our knowledge, this is the largest randomised controlled trial of a psychological intervention for a mental health problem. It provides strong evidence that insomnia is a causal factor in the occurrence of psychotic experiences and other mental health problems. Whether the results generalise beyond a student population requires testing. The treatment of disrupted sleep might require a higher priority in mental health provision. FUNDING: Wellcome Trust

Suicide trends in the early months of the COVID-19 pandemic: an interrupted time-series analysis of preliminary data from 21 countries

BackgroundThe COVID-19 pandemic is having profound mental health consequences for many people. Concerns have been expressed that at its most extreme, this may manifest itself in increased suicide rates.MethodsWe sourced real-time suicide data from around the world via a systematic internet search and recourse to our networks and the published literature. We used interrupted time series analysis to model the trend in monthly suicides prior to COVID-19 in each country/area-within-country, comparing the expected number of suicides derived from the model with the observed number of suicides in the early months of the pandemic. Countries/areas-within countries contributed data from at least 1 January 2019 to 31 July 2020 and potentially from as far back as 1 January 2016 until as recently as 31 October 2020. We conducted a primary analysis in which we treated 1 April to 31 July 2020 as the COVID-19 period, and two sensitivity analyses in which we varied its start and end dates (for those countries/areas-within-countries with data beyond July 2020).OutcomesWe sourced data from 21 countries (high income [n=16], upper-middle income [n=5]; whole country [n=10], area(s)-within-the-country [n=11]). In general, there does not appear to have been a significant increase in suicides since the pandemic began in the countries for which we had data. In fact, in a number of countries/areas-within-countries there appears to have been a decrease.InterpretationThis is the first study to examine suicides occurring in the context of the COVID-19 pandemic in multiple countries. It offers a consistent picture, albeit from high- and upper-middle income countries, of suicide numbers largely remaining unchanged or declining in the early months of the pandemic. We need to remain vigilant and be poised to respond if the situation changes as the longer-term mental health and economic impacts of the pandemic unfold

APrevent® Vocal Implant System (VOIS) zur externen Stimmlippenmedialisierung mit Nachjustiermöglichkeit - eine offene, nicht randomisierte Pilotstudie

Hintergrund: Permanente einseitige Rekurrensparesen mit Glottisschlussinsuffienz benötigen meistens eine externe Medialisationsthyroplastik Typ I (MT). Bisherige Implantate lassen keine nachträgliche Adjustierung im Falle einer Änderung der Stimmlippenstellung zu, weshalb immer wieder Revisionsoperationen notwendig werden. Ziel dieser Studie ist, das neue APrevent® VOIS-Implantat (VOIS), welches im Langzeitverlauf durch ein Ballonsystem nachjustiert werden kann, zu evaluieren.Material und Methoden: Seit 2018 wurde das VOIS erstmals in 8 Patienten bei geplanter MT intraoperativ eingesetzt, bevor das herkömmliche Titanium Vocal Fold Medialization Implant (TVFMI) eingesetzt wurde. Es sollten das operative Handling und stimmliche Outcome-Parameter beurteilt werden. Bei allen Patienten wurden intraoperativ akustische Stimmanalysen, Messungen der maximalen Phonationszeit (MPT) und Beurteilungen des Glottisschlusses vor der Implantation, nach Einsetzen des VOIS und des TVFMI durchgeführt. Die Daten wurden statistisch ausgewertet (Paardifferenzentest).Ergebnisse: Alle Patienten zeigten deutliche Besserung der Stimme und des Glottisschlusses nach Einsetzen sowohl des VOIS als auch des TVFMI. Die RBH-Werte besserten sich von präoperativ (R)2.13, (B)2.25, (H)2.50 zu (R)0.63, (B)0.25, (H)0.75 nach VOIS Implantation, MPT von präoperativ 7.9 sec zu 14.6 sec nach VOIS. Diese Ergebnisse waren mit den TVFMI-Ergebnissen vergleichbar. Das Einsetzen des VOIS verlief vom operativen Handling her problem- und komplikationslos.Diskussion: Das neu entwickelte VOIS-Implantat zeigte im Vergleich zum herkömmlich verwendeten Implantat TVFMI vergleichbare Ergebnisse der Stimmklangverbesserung und des Glottisschlusses. Eine Langzeitstudie mit VOIS ist geplant

Selektive Elektrostimulation (SELS) mit Oberflächenelektroden bei einseitiger Rekurrensparese (UVFP)

Hintergrund: SELS ist eine funktionelle elektrische Stimulation und eine interessante Behandlungsmöglichkeit für UVFP-Patienten. Bisher gilt die SELS noch nicht als Routinetherapie bei Stimmstörungen, da es bisher nicht möglich war, Stimulationsparameter so zu bestimmen, dass mittels Oberflächenelektroden eine selektive therapeutische elektrische Stimulation erreicht werden kann, ohne gleichzeitig Schmerzen oder Hautreizungen zu verursachen. Ziel dieser Studie war es, unterschiedliche SELS-Parameter hinsichtlich der Wirksamkeit bei UFVP zu untersuchen.Material und Methoden: 53 erwachsene UVFP-Patienten wurden mit dreiecksförmigen Pulsen (Pulsbreite (PW): 1, 10, 25, 50, 100, 250, 500 ms; Amplitude aufsteigend von 0,1 bis 20 mA) stimuliert. Es wurden zum einen nichtselektive Reaktionen (Schmerzen, Kontraktionen der Halsmuskeln, Schluckreflexauslösung) und zum anderen selektive Reaktionen (Adduktion der Stimmlippen in der Laryngoskopie) dokumentiert.Ergebnisse: Die Reizwahrnehmungsschwelle lag unter 5 mA und war umgekehrt proportional zur angelegten Pulsbreite (PW). Eine Schmerzschwelle unter 20 mA zeigten unabhängig von der PW weniger als 50% der Patienten. Eine effektive Stimmlippen-Adduktion wurde zwischen 6,8 und 8,4 mA bei PW von 50, 100 oder 250 ms beobachtet. Höhere PW korrelierten mit gesteigertem Schluckreflex und niedrigere mit erhöhter unspezifischer Aktivität der äußeren Halsmuskeln. Die Ergebnisse wurden durch die Dauer einer bereits bestehenden UVFP nicht beeinflusst.Diskussion: Unsere Studienergebnisse zeigen, dass es möglich ist, eine PW (50 oder 100 ms) und einen Amplitudenbereich (6,5 bis 8,5 mA) zu wählen, um eine SELS zu erhalten, die eine effektive Stimmlippen-Medialisierung bei UVFP-Patienten induziert, ohne Schmerz oder andere unerwünschte Ereignisse zu verursachen.Fazit: Diese Studie ist ein Beitrag für die routinemäßige Anwendung von oberflächlicher Elektrostimulation bei ausgewählten Stimmstörungen