COVID-19 has rapidly become a global challenge. 1 We read with interest the article by Bezzio et al 1 that reported the characteristics and outcomes of COVID-19 patients with pre-existing IBD. Patients with pre-existing cirrhosis, who have immune dysfunction and poorer outcomes from acute respiratory distress syndrome (ARDS) than patients without cirrhosis, are also considered a high-risk population for COVID-19. 2 3 In previous studies, the proportion of COVID-19 patients with pre-existing liver conditions ranged from 2% to 11%. 2 However, the clinical course and risk factors for mortality in these patients has not yet been reported. This retrospective multicentre study (COVID-Cirrhosis-CHESS, ClinicalTrials. gov NCT04329559) included consecutive adult patients with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and pre-existing cirrhosis from 16 designated hospitals in China between 31 December 2019 and 24 March 2020. Patient characteristics are summarised in table 1. Twenty-one COVID-19 patients with preexisting cirrhosis (Child-Pugh class A, B and C in 16, 3 and 2 patients, respectively) were included in the analysis. The median age was 68 years; 11 (52.4%) were male. Most patients had compensated cirrhosis (81.0%) and chronic HBV infection was the most common aetiology (57.1%). Comorbidities other than cirrhosis were present in most patients (66.7%). In previous studies, older age, male sex and pre-existing comorbidities were associated with higher risk of mortality for COVID-19. 4 5 Here, there were no significant differences between survivors (n=16) and non-survivors (n=5) in age, sex, comorbidities, aetiology of cirrhosis, stage of cirrhosis, Child-Pugh class, Model for End-stage Liver Disease (MELD) score, interval between onset and admission, or onset symptoms of COVID-19. Comorbidities have been associated with adverse outcomes in cirrhosis, 6 but our analysis did not show clear prognostic associations-possibly due to the small size and narrow composition of the study population.

SummaryCas9 nucleases can be programmed with single guide RNAs (sgRNAs) to mediate gene editing. High CRISPR/Cas9-mediated gene knockout efficiencies are essential for genetic screens and critically depend on the properties of the sgRNAs used. The specificity of an sgRNA is defined by its targeting sequence. Here, we discovered that two short sequence motifs at the 3′ end of the targeting sequence are almost exclusively present in inefficient sgRNAs of published sgRNA-activity datasets. By specific knock-in of sgRNA target sequences with or without these motifs and quantitative measurement of knockout efficiency, we show that the presence of these motifs in sgRNAs per se results in a 10-fold reduction of gene knockout frequencies. Mechanistically, the cause of the low efficiency differs between the two motifs. These sequence motifs are relevant for future sgRNA design approaches and studies of Cas9-DNA interactions.

Asthma is characterized by chronic endobronchial inflammation and the deposition of collagen below the epithelial basement membrane. The functional significance of collagen deposition is unknown, but it can lead to loss of airway distensibility and hence to eventual loss of bronchodilator response. In this study we examined the volume of airway dead space by a single-breath, nitrogen-plateau method at a range of lung volumes during inspiration. Participants were 10 asthmatics and 10 control subjects who were matched for lung volumes and age. The asthmatics increased their dead space by 27.0 ml/L compared with 37.3 ml/L in the control subjects (p = 0.014). The dead-space volumes at 50% TLC were no different (29.3 ml/L lung volume in asthma versus 26.9 ml/L in control subjects, p = 0.25). Loss of airway distensibility did not correlate, however, with loss of bronchodilator responsiveness, implying that factors other than mechanical airway distensibility may act to determine pharmacologic reversibility of airflow obstruction.

S rc is a membrane-bound tyrosine kinase(1) that has been implicated in the progression of many human cancers (2,3) including tumors of the breast, (4-6) kidney, (7) and prostate. (8) The Src kinase phosphorylates Cas (Crk-associated substrate) and activates mitogen-activated protein kinase (MAPK) to promote anchorage-independent growth and migration. (9)(10)(11)(12)(13)(14)(15)(16) These fundamental hallmarks of tumor-cell growth are required for metastasis and distinguish most cancer cells from their non-transformed precursors. (17,18) We have recently found that Src utilizes Cas to inhibit Fhl1 (four and a half LIM domains 1) expression, in order to promote non-anchored cell growth and migration. (19) Transfection studies show that Fhl1 specifically blocks non-anchored tumor-cell growth and migration, but does not affect 'normal' anchored cell growth. Therefore, Fhl1 acts as a true tumor suppressor rather than as a general mitotic inhibitor. (19) As the name indicates, Fhl1 consists of 'four and a half LIM domains'. Fhl1 can move between intercellular junctions, (20) focal adhesions, and the nucleus (21) to affect gene expression. (22,23) For example, Fhl1 associates with the recombination signal binding protein for immunoglobulin kappa J region (RBP-J)-DNA binding protein to modulate gene transcription. (22,23)

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