Key Points Loss-of-function mutations in CD37 occur predominantly in diffuse large B-cell lymphoma at immune-privileged sites. CD37-mutated lymphoma B cells show impaired CD37 cell-surface localization, which may have implications for anti-CD37 therapies.

Key Pointsr Patients with transposition of the great arteries (TGA) and systemic right ventricles have premature congestive heart failure; there is also a growing concern that athletes who perform extraordinary endurance exercise may injure the right ventricle.r Therefore we felt it essential to determine whether exercise training might injure a systemic right ventricle which is loaded with every heartbeat.r Previous studies have shown that short term exercise training is feasible in TGA patients, but its effect on ventricular function is unclear.r We demonstrate that systemic right ventricular function is preserved (and may be improved) in TGA patients with exercise training programmes that are typical of recreational and sports participation, with no evidence of injury on biomarker assessment.r Stroke volume reserve during exercise correlates with exercise training response in our TGA patients, identifying this as a marker of a systemic right ventricle (SRV) that may most tolerate (and possibly even be improved by) exercise training.Abstract We aimed to assess the haemodynamic effects of exercise training in transposition of the great arteries (TGA) patients with systemic right ventricles (SRVs). TGA patients have limited exercise tolerance and early mortality due to systemic (right) ventricular failure. Whether exercise training enhances or injures the SRV is unclear. Fourteen asymptomatic patients (34 ± 10 years) with TGA and SRV were enrolled in a 12 week exercise training programme (moderate and high-intensity workouts). Controls were matched on age, gender, BMI and physical activity. Exercise testing pre-and post-training included: (a) submaximal and peak; (b) prolonged (60 min) submaximal endurance and (c) high-intensity intervals. Oxygen uptake (V O 2 ; Douglas bag technique), cardiac output (Q c , foreign-gas rebreathing), ventricular function (echocardiography and cardiac MRI) and serum biomarkers were assessed. TGA patients had lower peakV O 2 ,Q c , and stroke volume (SV), a bluntedQ c /V O 2 slope, and diminished SV response to exercise (SV increase from rest: TGA = 15.2%, controls = 68.9%, P < 0.001) compared with controls. After training, TGA patients increased peakV O 2 by 6 ± 8.5%, similar to controls (interaction P = 0.24). The magnitude of SV reserve on initial testing correlated witḣ Q c training response (r = 0.58, P = 0.047), though overall, no change in peakQ c was observed. High-sensitivity troponin T (hs-TnT) and N-terminal prohormone of brain naturetic peptide (NT pro-BNP) were low and did not change with acute exercise or after training. Our data show that TGA patients with SRVs in this study safely participated in exercise training and improved peakV O 2 . Neither prolonged submaximal exercise, nor high-intensity intervals, nor short-term exercise training seem to injure the systemic right ventricle.

Diffuse large B-cell lymphoma (DLBCL) represents the most common form of non-Hodgkin lymphoma that is still incurable in a large fraction of patients. Tetraspanin CD37 is highly expressed on mature B lymphocytes and multiple CD37-targeting therapies are under clinical development for non-Hodgkin lymphoma. However, CD37 expression is non-detectable in ~50% of DLBCL patients which correlates with inferior treatment outcome, but the underlying mechanisms for differential CD37 expression in DLBCL are still unknown. Here, we investigated the regulation of the CD37 gene in human DLBCL at the (epi-)genetic and transcriptional level. No differences were observed in DNA methylation within the CD37 promoter region between CD37-positive and CD37-negative primary DLBCL patient samples. On the contrary, CD37-negative DLBCL cells specifically lacked CD37 promoter activity, suggesting differential regulation of CD37 gene expression. Using an unbiased quantitative proteomic approach, we identified transcription factor IRF8 to be significantly higher expressed in nuclear extracts of CD37-positive as compared to CD37-negative DLBCL. Direct binding of IRF8 to the CD37 promoter region was confirmed by DNA pull-down assay combined with mass spectrometry, and targeted chromatin immunoprecipitation. Functional analysis indicated that IRF8 overexpression enhanced CD37 protein expression, while CRISPR/Cas9 knock-out of IRF8 decreased CD37 levels in DLBCL cell lines. Immunohistochemical analysis in a large cohort of primary DLBCL (n=206) revealed a significant correlation of IRF8 expression with detectable CD37 levels. Together, this study provides new insight into the molecular mechanisms underlying differential CD37 expression in human DLBCL, and reveals IRF8 as transcriptional regulator of CD37 in B-cell lymphoma.

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The specific interaction of the RNA recognition motif of Rev and its viral mRNA target, RRE, has been demonstrated for the first time at the single-molecule level by atomic-force-microscope based single-molecule-force-spectroscopy (AFM-SMFS). The approach reveals details of the dissociation pathway and contribution of base mutations. Specific RNA-protein interaction is efficiently blocked by the RNA binding agent neomycin, showing the potential of AFM-SMFS as an efficient tool for singlemolecule drug screening of RNA targets. Furthermore, we show the importance of surface chemistry in AFM-SMFS of RNA-protein interaction, in particular the influence of polymer linkers.

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Investigations of bonds between single molecules and molecular complexes by dynamic force spectroscopy are subject to large fluctuations at nanoscale and possible aspecific binding, which mask the experimental output. Big efforts are devoted to develop methods for the effective selection of the relevant experimental data, before the quantitative analysis of bond parameters. Here we present a methodology which is based on the application of graph theory. The forcedistance curves corresponding to repeated pulling events are mapped onto their correlation network (mathematical graph). On these graphs the groups of similar curves appear as topological modules, which are identified using the spectral analysis of graphs. We demonstrate the approach by analyzing a large ensemble of the force-distance curves measured on: ssDNA-ssDNA, peptide-RNA (from HIV1), and peptide-Au surface systems. Within our data sets the methodology systematically separates subgroups of curves which are related to different types of intermolecular interactions and to spatial arrangements in which the molecules are brought together and/or pulling speeds. This demonstrates the sensitivity of the method to the spatial degrees of freedom, suggesting potential applications in the case of large molecular complexes and situations with multiple binding sites.