Conservative site-specific and single-copy transgenesis in human LINE-1 elements.

Genome engineering of human cells plays an important role in biotechnology and molecular medicine. In particular, insertions of functional multi-transgene cassettes into suitable endogenous sequences will lead to novel applications. Although several tools have been exploited in this context, safety issues such as cytotoxicity, insertional mutagenesis and off-target cleavage together with limitations in cargo size/expression often compromise utility. Phage λ integrase (Int) is a transgenesis tool that mediates conservative site-specific integration of 48 kb DNA into a safe harbor site of the bacterial genome. Here, we show that an Int variant precisely recombines large episomes into a sequence, term edattH4X, found in 1000 human Long INterspersed Elements-1 (LINE-1). We demonstrate single-copy transgenesis through attH4X-targeting in various cell lines including hESCs, with the flexibility of selecting clones according to transgene performance and downstream applications. This is exemplified with pluripotency reporter cassettes and constitutively expressed payloads that remain functional in LINE1-targeted hESCs and differentiated progenies. Furthermore, LINE-1 targeting does not induce DNA damage-response or chromosomal aberrations, and neither global nor localized endogenous gene expression is substantially affected. Hence, this simple transgene addition tool should become particularly useful for applications that require engineering of the human genome with multi-transgenes.

Comparison of adverse events associated with different spacers used with non-extrafine beclometasone dipropionate for asthma.

Co-prescription of Aerochamber® spacer with non-extrafine beclometasone diproprionate (non-EF BDP) is common but unlicensed. We report a comparison of inhaled corticosteroid (ICS)-related adverse events between patients co-prescribed Aerochamber compared to the licensed Volumatic® spacer. We utilised two historical cohorts: questionnaire-based and electronic medical record (EMR)-based, to assess patient-reported and EMR-recorded adverse events in patients with asthma prescribed non-EF BDP. Marginal effect estimate (MEE) was calculated to determine non-inferiority of Aerochamber compared to Volumatic in terms of patient-reported oral thrush and hoarseness with margin of 0.13. Other patient-reported adverse events (sore throat, bruising, weight gain, and coughing), and EMR-recorded adverse events were also assessed. Rate of patient-reported oral adverse events were non-inferior in 385 patients prescribed Aerochamber compared to 155 patients prescribed Volumatic (27.7 vs 29.9%; MEE, -0.043; 95% CI, -0.133 to 0.047). Total patient-reported adverse events did not differ significantly between Aerochamber and Volumatic (53.3 vs 49.7% with ≥1 adverse event). The EMR-based study of 1471 matched pairs of subjects did not show significantly different number of EMR-recorded adverse events between Aerochamber and Volumatic (12.5 vs 12.8% with ≥1 adverse events). Co-prescribing Aerochamber with non-EF BDP does not increase the risk for patient-reported and EMR-recorded ICS-related adverse events compared to co-prescribing Volumatic.

Fractional exhaled nitric oxide as a predictor of response to inhaled corticosteroids in patients with non-specific respiratory symptoms and insignificant bronchodilator reversibility: a randomised controlled trial.

BACKGROUND: Chronic non-specific respiratory symptoms are difficult to manage. This trial aimed to evaluate the association between baseline fractional exhaled nitric oxide (FeNO) and the response to inhaled corticosteroids in patients with non-specific respiratory symptoms. METHODS: In this double-blind randomised placebo-controlled trial, we enrolled undiagnosed patients, aged 18-80 years, with cough, wheeze, or dyspnoea and less than 20% bronchodilator reversibility across 26 primary care centres and hospitals in the UK and Singapore. Patients were assessed for 2 weeks before being randomly assigned (1:1) to 4 weeks of treatment with extrafine inhaled corticosteroids (QVAR 80 µg, two puffs twice per day, equivalent to 800 µg per day beclomethasone dipropionate) or placebo. Randomisation was stratified by baseline FeNO measurement: normal (≤25 parts per billion [ppb]), intermediate (>25 tp <40 ppb), and high (≥40 ppb). The primary endpoint was change in Asthma Control Questionnaire (ACQ7) mean score. We used generalised linear modelling to assess FeNO as a predictor of response, estimating an interaction effect between FeNO and treatment on change in ACQ7. We did our primary and secondary analyses in the per-protocol set, which excluded patients with non-completion of the primary endpoint, non-compliance to treatment (ascertained by patient report), and study visits made outside the predefined visit windows. This study is registered on ClinicalTrials.gov, number NCT02294279. FINDINGS: Between Feb 4, 2015, and July 12, 2016, we randomly assigned 294 patients to extrafine inhaled corticosteroid treatment (n=148) or placebo (n=146). Following exclusions due to protocol violations, we analysed 214 patients (114 extrafine inhaled corticosteroids and 100 placebo). We observed a significant interaction between baseline FeNO and treatment group for every 10 ppb increase in baseline FeNO, with the change in ACQ7 greater in the extrafine inhaled corticosteroids group than in the placebo group (difference between groups 0·071, 95% CI 0·002 to 0·139; p=0·044). The most common adverse events were nasopharyngitis (18 [12%] patients in the treatment group vs 13 [9%] in the placebo group), infections and infestations (25 [17%] vs 21 [14%]), and respiratory, thoracic, and mediastinal disorders (13 [9%] vs 17 [12%]). INTERPRETATION: FeNO measurement is an easy and non-invasive tool to use in clinical practice in patients with non-specific respiratory symptoms to predict response to inhaled corticosteroids. Further research is needed to examine its role in patients with evidence of other airway diseases, such as chronic obstructive pulmonary disease. FUNDING: Sponsored by OPRI with partial funding by Circassia and study drugs provided by TEVA.

TopoIIα prevents telomere fragility and formation of ultra thin DNA bridges during mitosis through TRF1-dependent binding to telomeres.

Telomeres are repetitive nucleoprotein structures at the ends of chromosomes. Like most genomic regions consisting of repetitive DNA, telomeres are fragile sites prone to replication fork stalling and generation of chromosomal instability. In particular, abrogation of the TRF1 telomere binding protein leads to stalled replication forks and aberrant telomere structures known as "multitelomeric signals". Here, we report that TRF1 deficiency also leads to the formation of "ultra-fine bridges" (UFB) during mitosis, and to an increased time to complete mitosis mediated by the spindle assembly checkpoint proteins (SAC). We find that topoisomerase IIα (TopoIIα), an enzyme essential for resolution of DNA replication intermediates, binds telomeres in a TRF1-mediated manner. Indeed, similar to TRF1 abrogation, TopoIIα downregulation leads to telomere fragility and UFB, suggesting that these phenotypes are due to decreased TopoIIα at telomeres. We find that SAC proteins bind telomeres in vivo, and that this is disrupted upon TRF1 deletion. These findings suggest that TRF1 links TopoIIα and SAC proteins in a pathway that ensures correct telomere replication and mitotic segregation, unveiling how TRF1 protects from telomere fragility and mitotic defects.