Pop-up Langmuir probe diagnostic in the water cooled divertor of Wendelstein 7-X.

The design, development, and successful implementation of pop-up Langmuir probes installed in the water-cooled divertor of W7-X are described. The probes are controlled by drive coils (actuators) installed behind the divertor plates. These drive coils make use of the magnetic field in W7-X to move the probe tips into and out of the plasma. The drive coils were installed in the vacuum vessel after extensively testing the durability of the coils and analyzing the criteria for safe operation. The probe design is carefully tailored for each of the 36 probe tips in order to be suitable for the different magnetic field configurations used in W7-X and ensure that the probes do not present leading edges to the magnetic flux tubes. An electronic bridge circuit is used for measurement to compensate for the effects of signal propagation time on the long cable lengths used. The diagnostic is integrated with the segment control of W7-X for automated operation and control of the diagnostic. The evaluation of the results from the plasma operation is presented after accounting for appropriate sheath expansion for negative bias voltage on the probes.

Extracellular heat shock protein 70 levels in tumour-bearing dogs and cats treated with radiation therapy and hyperthermia.

Hyperthermia is a form of a cancer treatment which is frequently applied in combination with radiotherapy (RT) to improve therapy responses and radiosensitivity. The mode of action of hyperthermia is multifactorial; the one hand by altering the amount of the blood circulation in the treated tissue, on the other hand by modulating molecular pathways involved in cell survival processes and immunogenic interactions. One of the most dominant proteins induced by hyperthermia is the major stress-inducible heat shock protein 70 (Hsp70). Hsp70 can be found in the blood either as a free-protein (free HSP70) derived from necrotic cells, or lipid-bound (liposomal Hsp70) when it is actively released in extracellular vesicles (EVs) by living cells. The aim of the study was to evaluate the levels of free and liposomal Hsp70 before and after treatment with RT alone or hyperthermia combined with radiotherapy (HTRT) in dogs and cats to evaluate therapy responses. Peripheral blood was collected from feline and canine patients before and at 2, 4, 6 and 24 h after treatment with RT or HTRT. Hsp70 enzyme-linked immunosorbent assays (ELISAs) were performed to determine the free and liposomal Hsp70 concentrations in the serum. The levels were analysed after the first fraction of radiation to study immediate effects and after all applied fractions to study cumulative effects. The levels of free and liposomal Hsp70 levels in the circulation were not affected by the first singular treatment and cumulative effects of RT in cats however, after finalizing all treatment cycles with HTRT free and liposomal Hsp70 levels significantly increased. In dogs, HTRT, but not treatment with RT alone, significantly affected liposomal Hsp70 levels during the first fraction. Free Hsp70 levels were significantly increased after RT, but not HTRT, during the first fraction in dogs. In dogs, on the other hand, RT alone resulted in a significant increase in liposomal Hsp70, but HTRT did not significantly affect the liposomal Hsp70 when cumulative effects were analysed. Free Hsp70 was significantly induced in dogs after both, RT and HTRT when cumulative effects were analysed. RT and HTRT treatments differentially affect the levels of free and liposomal Hsp70 in dogs and cats. Both forms of Hsp70 could potentially be further investigated as potential liquid biopsy markers to study responses to RT and HTRT treatment in companion animals.

Large granular lymphocyte lymphoma with leukemic phase and suspicion of leptomeningeal lymphomatosis in a cat - a case report.

INTRODUCTION: In this case report we present a feline large granular lymphocyte (LGL) lymphoma, a rare morphologically distinct subtype of lymphoma, in a twelve-year-old female spayed domestic short hair cat, with high suspicion of leptomeningeal lymphomatosis due to magnetic resonance imaging findings and results of cerebral spinal fluid analyses. Diagnosis of LGL lymphoma was confirmed by means of blood cytology and polymerase chain reaction for antigen receptor rearrangements.

INTRODUCTION: Dans ce rapport de cas, nous présentons un Large Granular Lymphocyte (LGL) lymphome, un sous-type rare de lymphome, chez une chatte domestique à poil court stérilisée de douze ans, avec une forte suspicion de lymphomatose leptoméningée en raison des résultats de l'imagerie par résonance magnétique et de l'analyse du liquide céphalo-rachidien. Le diagnostic de LGL-lymphome a été confirmé par une cytologie sanguine et une réaction en chaîne de la polymérase pour les réarrangements des récepteurs d'antigènes.

Quantification of patellar tendon strain and opportunities for personalized tendon loading during back squats.

Tendon strain during exercise is a critical regulatory factor in tendon adaptive responses and there are indications for an optimal range of strain that promotes tendon adaptation. Back squats are used to improve patellar tendon properties in sport and clinical settings. To date, the operating patellar tendon strain during back squats is unknown and current recommendations for individual exercise loading are based on the one repetition maximum (1RM). Here, we quantified patellar tendon strain during loaded back squats at 40, 60 and 80% of the 1RM and during maximum isometric knee extension contractions (MVC) using ultrasonography. Kinematics, ground reaction forces and muscle electromyographic activity were also recorded. Additionally, maximum tendon strain during the MVC and the percentage of 1RM were used as explanatory variables to estimate the individual patellar tendon strain during the squats. Strain increased with increasing 1RM loading (4.7 to 8.2%), indicating that already medium-loading back squats may provide a sufficient stimulus for tendon adaptation. The individual variability was, however, too high to generalize these findings. Yet, there was a high agreement between the individually estimated and measured patellar tendon strain (R2 = 0.858) during back squats. We argue that this approach may provide new opportunities for personalized tendon exercise.

Stability recovery performance in adults over a wide age range: A multicentre reliability analysis using different lean-and-release test protocols.

The ability to effectively increase the base of support is crucial to prevent from falling due to stability disturbances and has been commonly assessed using the forward-directed lean-and-release test. With this multicentre study we examined whether the assessment of stability recovery performance using two different forward lean-and-release test protocols is reliable in adults over a wide age range. Ninety-seven healthy adults (age from 21 to 80 years) were randomly assigned to one out of two lean angle protocols: gradual increase to maximal forward-lean angle (maximal lean angle; n = 43; seven participants were excluded due to marker artefacts) or predefined lean angle (single lean angle; n = 26; 21 participants needed to be excluded due to multiple stepping after release or marker artefacts). Both protocols were repeated after 0.5 h and 48 h to investigate intra- and inter-session reliability. Stability recovery performance was examined using the margin of stability at release (MoSRL) and touchdown (MoSTD) and increase in base of support (BoSTD). Intraclass correlation coefficients (confidence intervals at 95%) for the maximal lean angle and for the single lean angle were respectively 0.93 (0.89-0.96) and 0.94 (0.89-0.97) in MoSRL, 0.85 (0.77-0.91) and 0.67 (0.48-0.82) in MoSTD and 0.88 (0.81-0.93) and 0.80 (0.66-0.90) in BoSTD, with equivalence being revealed for each parameter between all three measurements (p < 0.01). We concluded that the assessment of stability recovery performance parameters in adults over a wide age range with the means of the forward lean-and-release test is reliable, independent of the used lean angle protocol.

Epidemiology and transmission characteristics of early COVID-19 cases, 20 January-19 March 2020, in Bavaria, Germany.

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) led to a significant disease burden and disruptions in health systems. We describe the epidemiology and transmission characteristics of early coronavirus disease 2019 (COVID-19) cases in Bavaria, Germany. Cases were reverse transcription polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infections, reported from 20 January-19 March 2020. The incubation period was estimated using travel history and date of symptom onset. To estimate the serial interval, we identified pairs of index and secondary cases. By 19 March, 3546 cases were reported. A large proportion was exposed abroad (38%), causing further local transmission. Median incubation period of 256 cases with exposure abroad was 3.8 days (95%CI: 3.5-4.2). For 95% of infected individuals, symptom onset occurred within 10.3 days (95%CI: 9.1-11.8) after exposure. The median serial interval, using 53 pairs, was 3.5 days (95%CI: 3.0-4.2; mean: 3.9, s.d.: 2.2). Travellers returning to Germany had an important influence on the spread of SARS-CoV-2 infections in Bavaria in early 2020. Especially in times of low incidence, public health agencies should identify holiday destinations, and areas with ongoing local transmission, to monitor potential importation of SARS-CoV-2 infections. Travellers returning from areas with ongoing community transmission should be advised to quarantine to prevent re-introductions of COVID-19.

[Foundations of Volumetric capnography : Principles of monitoring of metabolism and hemodynamics]. / Grundlagen der Volumetrischen Kapnographie : Prinzipien der Überwachung von Stoffwechsel und Hämodynamik.

Capnography is the graphical representation of the carbon dioxide (CO2) concentration in expired air. Using this monitoring procedure, the kinetics of CO2 of mechanically ventilated patients can be assessed in a noninvasive way and in real time. This article highlights the importance, particularly of volumetric capnography (VCap), for clinical monitoring of mechanically ventilated patients. The procedure provides important information on the breathing, ventilation, metabolism and hemodynamics of patients.

[Volumetric capnography for analysis and optimization of ventilation and gas exchange]. / Volumetrische Kapnographie zur Analyse und Optimierung von Ventilation und Gasaustausch.

Capnography as the graphical representation of the expiratory carbon dioxide (CO2) concentration, is an essential component of monitoring of every ventilated patient, in addition to pulse oximetry. Capnography demonstrates the kinetics of CO2 in a noninvasive way and in real time. In the daily routine anesthesia, it mainly serves for identification of the correct intubation and adaptation of the respiratory minute volume to be applied; however, capnography can also provide much more far-reaching and clinically particularly valuable information, especially in the form of volumetric capnography (VCap) that is not yet so widely clinically available. These include monitoring and optimization of ventilation and assessment of gas exchange. This article presents parameters for making decisions at the bedside, which could previously only be obtained by extensive, more invasive, nonautomated procedures.

The PBS Score - a clinical assessment tool for the ambulatory and recurrent clubfoot.

PURPOSE: The signs for clubfoot relapse are poorly defined in the literature and there is a lack of a scoring system that allows assessment of clubfeet in ambulatory children. The aim of this study is to develop an easy to use, reliable and validated evaluation tool for ambulatory children with a history of clubfoot. METHODS: A total of 52 feet (26 children, 41 clubfeet, 11 unaffected feet) were assessed. Three surgeons used the seven-item PBS Score to rate hindfoot varus, standing and walking supination, early heel rise, active/passive ankle dorsiflexion and subtalar abduction blinded to the other examiners. All parents answered the modified Roye score questionnaire prior to the clinical assessment. Correlation between the mean PBS Score and the Roye score was evaluated using Spearman's rank correlation coefficient. Interobserver reliability was tested using weighted and unweighted Cohen's Kappa coefficients. RESULTS: The Spearman's rank correlation coefficient for correlation between mean PBS Score and Roye score was 0.73 (moderate to good correlation).The interobserver agreement for the total PBS Score resulted in an intraclass correlation coefficient of 0.93 (almost perfect agreement). CONCLUSION: The PBS score is an easy to use, clinical assessment tool for walking age children with clubfoot deformity. It includes passive and active criteria with a very good interobserver reliability and moderate to good validity. LEVEL OF EVIDENCE: Level I - Diagnostic study.

Monitoring of tidal ventilation by electrical impedance tomography in anaesthetised horses.

BACKGROUND: Electrical impedance tomography (EIT) is a method to measure regional impedance changes within the thorax. The total tidal impedance variation has been used to measure changes in tidal volumes in pigs, dogs and men. OBJECTIVES: To assess the ability of EIT to quantify changes in tidal volume in anaesthetised mechanically ventilated horses. STUDY DESIGN: In vivo experimental study. METHODS: Six horses (mean ± s.d.: age 11.5 ± 7.5 years and body weight 491 ± 40 kg) were anaesthetised using isoflurane in oxygen. The lungs were mechanically ventilated using a volume-controlled mode. With an end-tidal carbon dioxide tension in the physiological range, and a set tidal volume (VTvent ) of 11-16 mL/kg (baseline volume), EIT data and VT measured by conventional spirometry were collected over 1 min. Thereafter, VTvent was changed in 1 L steps until reaching 10 L. After, VTvent was reduced to 1 L below the baseline volume and then further reduced in 1 L steps until 4 L. On each VT step data were recorded for 1 min after allowing 1 min of stabilisation. Impedance changes within the predefined two lung regions of interest (EITROI ) and the whole image (EITthorax ) were calculated. Linear regression analysis was used to assess the relationship between spirometry data and EITROI and EITthorax for individual horses and pooled data. RESULTS: Both EITROI and EITthorax significantly predicted spirometry data for individual horses with R2 ranging from 0.937 to 0.999 and from 0.954 to 0.997 respectively. This was similar for pooled data from all six horses with EITROI (R2 = 0.799; P<0.001) and EITthorax (R2 = 0.841; P<0.001). MAIN LIMITATIONS: The method was only tested in healthy mechanically ventilated horses. CONCLUSIONS: The EIT can be used to quantify changes in tidal volume.

Operating length and velocity of human vastus lateralis muscle during walking and running.

According to the force-length-velocity relationships, the muscle force potential during locomotion is determined by the operating fibre length and velocity. We measured fascicle and muscle-tendon unit length and velocity as well as the activity of the human vastus lateralis muscle (VL) during walking and running. Furthermore, we determined the VL force-length relationship experimentally and calculated the force-length and force-velocity potentials (i.e. fraction of maximum force according to the force-length-velocity curves) for both gaits. During the active state of the stance phase, fascicles showed significantly (p < 0.05) smaller length changes (walking: 9.2 ± 4.7% of optimal length (L0); running: 9.0 ± 8.4%L0) and lower velocities (0.46 ± 0.36 L0/s; 0.03 ± 0.83 L0/s) compared to the muscle-tendon unit (walking: 19.7 ± 5.3%L0, -0.94 ± 0.32 L0/s; running: 34.5 ± 5.8%L0, -2.59 ± 0.41 L0/s). The VL fascicles operated close to optimum length (L0 = 9.4 ± 0.11 cm) in both walking (8.6 ± 0.14 cm) and running (10.1 ± 0.19 cm), resulting in high force-length (walking: 0.92 ± 0.08; running: 0.91 ± 0.14) and force-velocity (0.91 ± 0.08; 0.97 ± 0.13) potentials. For the first time we demonstrated that, in contrast to the current general conception, the VL fascicles operate almost isometrically and close to L0 during the active state of the stance phase of walking and running. The findings further verify an important contribution of the series-elastic element to VL fascicle dynamics.

Detection of thoracic vascular structures by electrical impedance tomography: a systematic assessment of prominence peak analysis of impedance changes.

OBJECTIVE: Electrical impedance tomography (EIT) is a non-invasive and radiation-free bedside monitoring technology, primarily used to monitor lung function. First experimental data shows that the descending aorta can be detected at different thoracic heights and might allow the assessment of central hemodynamics, i.e. stroke volume and pulse transit time. APPROACH: First, the feasibility of localizing small non-conductive objects within a saline phantom model was evaluated. Second, this result was utilized for the detection of the aorta by EIT in ten anesthetized pigs with comparison to thoracic computer tomography (CT). Two EIT belts were placed at different thoracic positions and a bolus of hypertonic saline (10 ml, 20%) was administered into the ascending aorta while EIT data were recorded. EIT images were reconstructed using the GREIT model, based on the individual's thoracic contours. The resulting EIT images were analyzed pixel by pixel to identify the aortic pixel, in which the bolus caused the highest transient impedance peak in time. MAIN RESULTS: In the phantom, small objects could be located at each position with a maximal deviation of 0.71 cm. In vivo, no significant differences between the aorta position measured by EIT and the anatomical aorta location were obtained for both measurement planes if the search was restricted to the dorsal thoracic region of interest (ROIs). SIGNIFICANCE: It is possible to detect the descending aorta at different thoracic levels by EIT using an intra-aortic bolus of hypertonic saline. No significant differences in the position of the descending aorta on EIT images compared to CT images were obtained for both EIT belts.

Exercises of dynamic stability under unstable conditions increase muscle strength and balance ability in the elderly.

The purpose of this study was to assess the effectiveness of a specific exercise intervention of mechanisms to control dynamic postural stability under unstable conditions in old adults. Forty-seven old adults (65-80 years) were assigned to 2 experimental groups (muscle strength group, n = 15; perturbation-based group, n = 16) and a control group (n = 16). The strength group performed resistance exercises for leg and trunk muscles, while the perturbation-based group exercised mechanisms of dynamic stability under unstable conditions. The training duration was 14 weeks, with training sessions twice a week for 1.5 hours. Muscle strength, balance ability, and balance recovery performance were investigated before and after the interventions using maximal isometric plantar flexion and knee extension contractions, the approach of the center of pressure to the anterior limits of stability and simulated forward falls. Both interventions increased balance recovery performance in simulated forward falls (81%, d = 1.50 and 80%, d = 1.08 in the muscle strength and perturbation-based group, respectively), while the control group did not show any changes. Plantar flexor strength increased 20% (d = 0.72) in the muscle strength and 23% (d = 1.03) in the perturbation-based group, while muscle strength of the knee extensors increased only in the muscle strength group (8%, d = 0.76). On the other hand, only the perturbation-based group showed a significant improvement of standing balance ability (38%, d = 1.61). We conclude that a perturbation-based training program focusing on exercising mechanisms of dynamic stability in unstable conditions has the potential to enhance muscle strength as well as sensory information processing within the motor system during sudden and static balance tasks and, as a consequence, reduce the risk of falls in old adults.

[Diverticulitis : Domain of conservative or drug therapy?] / Divertikulitis : Domäne der konservativen bzw. medikamentösen Therapie?

Increasing interest in diverticular disease by the scientific community in the last 10-15 years has resulted in an increased number of publications. Among other things, nonevidence-based therapeutic paradigms were tested in randomized, controlled therapy studies. The importance of surgery in the therapy of diverticulitis has diminished in recent years; in particular, it has no role in the treatment of diverticulitis types 1a, 1b, and 2a according to the Classification of Diverticular Disease (CDD) treated successfully by conservative means. Surgery has only a subordinate role in recurrent type 3b diverticulitis according to the CDD. Diverticulitis is therefore increasingly treated using conservative or drug therapy. However, only the classic, established antibiotics are currently available as effective drugs for the treatment of diverticular disease. However, these are also decreasing in significance. Over 90% of patients with type 1a/1b diverticulitis can be safely treated according to current data without the use of antibiotics. It is possible that type 2a diverticulitis will also be successfully treated without antibiotics in the future. Substances such as rifaximin, mesalazine, or probiotics, which were tested above all in patients with chronic recurrent forms (CDD type 3a/3b), have not yet been established.

Electrical impedance tomography for non-invasive assessment of stroke volume variation in health and experimental lung injury.

BACKGROUND: Functional imaging by thoracic electrical impedance tomography (EIT) is a non-invasive approach to continuously assess central stroke volume variation (SVV) for guiding fluid therapy. The early available data were from healthy lungs without injury-related changes in thoracic impedance as a potentially influencing factor. The aim of this study was to evaluate SVV measured by EIT (SVVEIT) against SVV from pulse contour analysis (SVVPC) in an experimental animal model of acute lung injury at different lung volumes. METHODS: We conducted a randomized controlled trial in 30 anaesthetized domestic pigs. SVVEIT was calculated automatically analysing heart-lung interactions in a set of pixels representing the aorta. Each initial analysis was performed automatically and unsupervised using predefined frequency domain algorithms that had not previously been used in the study population. After baseline measurements in normal lung conditions, lung injury was induced either by repeated broncho-alveolar lavage (n=15) or by intravenous administration of oleic acid (n=15) and SVVEIT was remeasured. RESULTS: The protocol was completed in 28 animals. A total of 123 pairs of SVV measurements were acquired. Correlation coefficients (r) between SVVEIT and SVVPC were 0.77 in healthy lungs, 0.84 after broncho-alveolar lavage, and 0.48 after lung injury from oleic acid. CONCLUSIONS: EIT provides automated calculation of a dynamic preload index of fluid responsiveness (SVVEIT) that is non-invasively derived from a central haemodynamic signal. However, alterations in thoracic impedance induced by lung injury influence this method.

Muscle and tendon adaptation in adolescent athletes: A longitudinal study.

There is evidence that a non-uniform adaptation of muscle and tendon in young athletes results in increased tendon stress during mid-adolescence. The present longitudinal study investigated the development of the morphological and mechanical properties of muscle and tendon of volleyball athletes in a time period of 2 years from mid-adolescence to late adolescence. Eighteen elite volleyball athletes participated in magnetic resonance imaging and ultrasound-dynamometry sessions to determine quadriceps femoris muscle strength, vastus lateralis, medialis and intermedius morphology, and patellar tendon mechanical and morphological properties in mid-adolescence (16 ± 1 years) and late adolescence (18 ± 1 years). Muscle strength, anatomical cross-sectional area (CSA), and volume showed significant (P < 0.05) but moderate increases of 13%, 6%, and 6%, respectively. The increase of patellar tendon CSA (P < 0.05) was substantially greater (27%) and went in line with increased stiffness (P < 0.05; 25%) and reduced stress (P < 0.05; 9%). During late adolescence, a pronounced hypertrophy of the patellar tendon led to a mechanical strengthening of the tendon in relation to the functional and morphological development of the muscle. These adaptive processes may compensate the unfavorable relation of muscle strength and tendon loading capacity in mid-adolescence and might have implications on athletic performance and tendon injury risk.

Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography.

BACKGROUND: Lung-protective ventilation is claimed to be beneficial not only in critically ill patients, but also in pulmonary healthy patients undergoing general anaesthesia. We report the use of electrical impedance tomography for assessing regional changes in ventilation, during both spontaneous breathing and mechanical ventilation, in patients undergoing robot-assisted radical prostatectomy. METHODS: We performed electrical impedance tomography measurements in 39 patients before induction of anaesthesia in the sitting (M1) and supine position (M2), after the start of mechanical ventilation (M3), during capnoperitoneum and Trendelenburg positioning (M4), and finally, in the supine position after release of capnoperitoneum (M5). To quantify regional changes in lung ventilation, we calculated the centre of ventilation and 'silent spaces' in the ventral and dorsal lung regions that did not show major impedance changes. RESULTS: Compared with the awake supine position [2.3% (2.3)], anaesthesia and mechanical ventilation induced a significant increase in silent spaces in the dorsal dependent lung [9.2% (6.3); P<0.05]. Capnoperitoneum and the Trendelenburg position led to a significant increase in such spaces [11.5% (8.9)]. Silent space in the ventral lung remained constant throughout anaesthesia. CONCLUSION: Electrical impedance tomography was able to identify and quantify on a breath-by-breath basis circumscribed areas, so-called silent spaces, within healthy lungs that received little or no ventilation during general anaesthesia, capnoperitoneum, and different body positions. As these silent spaces are suggestive of atelectasis on the one hand and overdistension on the other, they might become useful to guide individualized protective ventilation strategies to mitigate the side-effects of anaesthesia and surgery on the lungs.

Hepatitis C viral dynamics during ribavirin priming differ according to prior treatment response and HCV type.

The mode of action of ribavirin is not completely understood. Ribavirin monotherapy has a measurable antiviral effect, which shows great variability. It might lead to an earlier steady state of plasma concentration and therefore enhance the effect of following combination treatment. The aim of this study was to evaluate the antiviral effect of ribavirin priming and its influence on sustained virologic response after combination treatment in a group of patients with different hepatitis C virus (HCV) types with or without prior treatment experience. Retrospective analysis of 75 patients (37 treatment naïve, 20 prior relapse, 16 prior nonresponse, genotype 1 present in 60 patients) from five centres who received ribavirin priming as part of an individual strategy in order to improve treatment outcome. All patients received ribavirin monotherapy with a mean dose of 14.5 mg kg-1 body weight for a mean of 28 days. After ribavirin priming, dual combination treatment with pegylated interferon alfa and ribavirin was started. The mean HCV RNA decline after ribavirin priming was 0.6 log10  IU mL-1 (P<.001). The initial viral decline depended on HCV type and previous treatment status being highest among prior relapsers (0.8 log10  IU mL-1 ; P=.002) and HCV type 2/3 (1.2 log10  IU mL-1 ; P=.05) and lowest among those with prior nonresponse (0.3 log10  IU mL-1 , P=.01). IFNL4 (formerly IL28B) genotype for rs12979860 and IFNL3 genotype rs8099917 did not influence the initial viral decline. The study demonstrates a significant variability in the viral dynamics and antiviral efficacy of ribavirin monotherapy, which is mainly influenced by prior treatment status. The fact that the lowest response pattern was observed in prior nonresponder patients to pegylated interferon alfa plus ribavirin combination therapy can be taken as a hint that not only the individual interferon, but also the ribavirin sensitivity contributes significantly to the nonresponsive state.

Splicing controls the ubiquitin response during DNA double-strand break repair.

Although evidence that splicing regulates DNA repair is accumulating, the underlying mechanism(s) remain unclear. Here, we report that short-term inhibition of pre-mRNA splicing by spliceosomal inhibitors impairs cellular repair of DNA double-strand breaks. Indeed, interference with splicing as little as 1 h prior to irradiation reduced ubiquitylation of damaged chromatin and impaired recruitment of the repair factors WRAP53ß, RNF168, 53BP1, BRCA1 and RAD51 to sites of DNA damage. Consequently, splicing-deficient cells exhibited significant numbers of residual γH2AX foci, as would be expected if DNA repair is defective. Furthermore, we show that this is due to downregulation of the E3 ubiquitin ligase RNF8 and that re-introduction of this protein into splicing-deficient cells restores ubiquitylation at sites of DNA damage, accumulation of downstream factors and subsequent repair. Moreover, downregulation of RNF8 explains the defective repair associated with knockdown of various splicing factors in recent genome-wide siRNA screens and, significantly, overexpression of RNF8 counteracts this defect. These discoveries reveal a mechanism that may not only explain how splicing regulates repair of double-strand breaks, but also may underlie various diseases caused by deregulation of splicing factors, including cancer.