MSH2/MSH6 Complex Promotes Error-Free Repair of AID-Induced dU:G Mispairs as well as Error-Prone Hypermutation of A:T Sites

Mismatch repair of AID-generated dU:G mispairs is critical for class switch recombination (CSR) and somatic hypermutation (SHM) in B cells. The generation of a previously unavailable Msh2−/−Msh6−/− mouse has for the first time allowed us to examine the impact of the complete loss of MutSα on lymphomagenesis, CSR and SHM. The onset of T cell lymphomas and the survival of Msh2−/−Msh6−/− and Msh2−/−Msh6−/−Msh3−/− mice are indistinguishable from Msh2−/− mice, suggesting that MSH2 plays the critical role in protecting T cells from malignant transformation, presumably because it is essential for the formation of stable MutSα heterodimers that maintain genomic stability. The similar defects on switching in Msh2−/−, Msh2−/−Msh6−/− and Msh2−/−Msh6−/−Msh3−/− mice confirm that MutSα but not MutSβ plays an important role in CSR. Analysis of SHM in Msh2−/−Msh6−/− mice not only confirmed the error-prone role of MutSα in the generation of strand biased mutations at A:T bases, but also revealed an error-free role of MutSα when repairing some of the dU:G mispairs generated by AID on both DNA strands. We propose a model for the role of MutSα at the immunoglobulin locus where the local balance of error-free and error-prone repair has an impact in the spectrum of mutations introduced during Phase 2 of SHM

COBRA Master Class: Providing deep-sea expedition leadership training to accelerate early career advancement

Leading deep-sea research expeditions requires a breadth of training and experience, and the opportunities for Early Career Researchers (ECRs) to obtain focused mentorship on expedition leadership are scarce. To address the need for leadership training in deep-sea expeditionary science, the Crustal Ocean Biosphere Research Accelerator (COBRA) launched a 14-week virtual Master Class with both synchronous and asynchronous components to empower students with the skills and tools to successfully design, propose, and execute deep-sea oceanographic field research. The Master Class offered customized and distributed training approaches and created an open-access syllabus with resources, including reading material, lectures, and on-line resources freely-available on the Master Class website (cobra.pubpub.org). All students were Early Career Researchers (ECRs, defined here as advanced graduate students, postdoctoral scientists, early career faculty, or individuals with substantial industry, government, or NGO experience) and designated throughout as COBRA Fellows. Fellows engaged in topics related to choosing the appropriate deep-sea research asset for their Capstone “dream cruise” project, learning about funding sources and how to tailor proposals to meet those source requirements, and working through an essential checklist of pre-expedition planning and operations. The Master Class covered leading an expedition at sea, at-sea operations, and ship-board etiquette, and the strengths and challenges of telepresence. It also included post-expedition training on data management strategies and report preparation and outputs. Throughout the Master Class, Fellows also discussed education and outreach, international ocean law and policy, and the importance and challenges of team science. Fellows further learned about how to develop concepts respectfully with regard to geographic and cultural considerations of their intended study sites. An assessment of initial outcomes from the first iteration of the COBRA Master Class reinforces the need for such training and shows great promise with one-quarter of the Fellows having submitted a research proposal to national funding agencies within six months of the end of the class. As deep-sea research continues to accelerate in scope and speed, providing equitable access to expedition training is a top priority to enable the next generation of deep-sea science leadership

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Global variations in diabetes mellitus based on fasting glucose and haemogloblin A1c

Fasting plasma glucose (FPG) and haemoglobin A1c (HbA1c) are both used to diagnose diabetes, but may identify different people as having diabetes. We used data from 117 population-based studies and quantified, in different world regions, the prevalence of diagnosed diabetes, and whether those who were previously undiagnosed and detected as having diabetes in survey screening had elevated FPG, HbA1c, or both. We developed prediction equations for estimating the probability that a person without previously diagnosed diabetes, and at a specific level of FPG, had elevated HbA1c, and vice versa. The age-standardised proportion of diabetes that was previously undiagnosed, and detected in survey screening, ranged from 30% in the high-income western region to 66% in south Asia. Among those with screen-detected diabetes with either test, the agestandardised proportion who had elevated levels of both FPG and HbA1c was 29-39% across regions; the remainder had discordant elevation of FPG or HbA1c. In most low- and middle-income regions, isolated elevated HbA1c more common than isolated elevated FPG. In these regions, the use of FPG alone may delay diabetes diagnosis and underestimate diabetes prevalence. Our prediction equations help allocate finite resources for measuring HbA1c to reduce the global gap in diabetes diagnosis and surveillance.peer-reviewe

Studying the role of BCL2 and MYC in the pathogenesis of diffuse large B cell lymphoma

Approximately 30% of patients with diffuse large B-cell lymphoma (DLBCL) co-express BCL2 and MYC, known as double-expressor lymphomas (DEL). These lymphomas associate with poorer prognosis and response to standard-of-care R-CHOP, and a preferred therapeutic alternative has not been identified yet. There are very interesting ongoing clinical trials to evaluate the potential of venetoclax to inhibit the anti-apoptotic protein BCL2 in high grade B cell lymphomas. Additionally, there are investigations ongoing trying to find a MYC inhibitor that can be efficiently used in the clinic without secondary effects. Here, we aimed to provide complementary preclinical in vivo evidences for these investigations, modelling this DEL-scenario in new mouse models and demonstrating that combination of anti-CD20 with BCL2 or MYC specific inhibitors can improve long-term survival in BCL2/MYC-expressor DLBCL mice. For this, we first generated and characterized three multi-transgenic mouse models and further demonstrated that it is possible to successfully recapitulate the complex progression and tumor microenvironment of DEL-DLBCL in the murine setting, recapitulating the classical genetic alterations of these patients by conditional mutagenesis at early stages of the germinal center reaction. We then demonstrated that lymphomas in these mice rapidly acquire aberrant BCL2/MYC co-expression and impair apoptosis during NF-κB-driven malignant transformation of germinal center B cells, hindering DLBCL cells sensitive to inhibition of BCL2 (with venetoclax) or MYC (with MYCi975). Then, we provided in vivo evidences that combination of venetoclax with anti-CD20-based immunotherapy can result in synergistic anti-lymphoma effects and extended overall survival of mice. Not only we demonstrated specific cell killing of BCL2/MYC co-expressing lymphoma cells in response to the combination treatment; but also, we revealed, for the first time in DLBCL, that venetoclax can promote the enrichment of activated intratumoral effector/effector memory CD8+ T cells, exhibiting additional immunomodulatory potential in the DEL-DLBCL tumor microenvironment. In addition, we demonstrated that acceleration of lymphomagenesis was evidenced when MYC expression was enforced from early stages of germinal center reaction. However, this lymphomagenesis was accompanied by the appearance of non-B-cells gastrointestinal tumors, possibly driven by the leakage of MYC expression, hence, resulting resistant to the conventional anti-CD20 immunotherapeutic regimen and to antibiotic treatment, impairing overall survival. Altogether, our results strongly support pre-clinical proof-of-concept and rationale for incorporating venetoclax to anti-CD20-based treatments to improve the outcome of aggressive DEL-DLBCL, and provide evidences for future combinations with specific MYC inhibitors, either incorporating them to the actual gold-standard R-CHOP or by dual targeting the Achilles heels of tumor cells through combined BCL2 and MYC specific inhibition. These preclinical combinations could either be performed in our murine models or in the novel 3D culture technique that we have successfully implemented here, which allows the long-term culture of lymphoma cells with its tumor microenvironment in the form of tumor spheroids and could serve as an ex vivo platform for future screening of novel therapeutic strategies in DLBCL.Aproximadamente un 30% de los pacientes con linfoma difuso de células B grandes (LDCBG) co-expresan BCL2 y MYC, los cuales se conocen como linfomas doble-expresantes (LDE). Estos linfomas se asocian con peor pronóstico y presentan peor respuesta al tratamiento estándar R-CHOP, y todavía no se han encontrado alternativas terapéuticas. Hay varios ensayos clínicos en marcha que evalúan el potencial de venetoclax para inhibir la proteína anti-apoptótica BCL2 en los linfomas de alto grado. También hay investigaciones en curso que intentan encontrar inhibidores específicos de MYC que se puedan usar de forma segura en la clínica. Por tanto, nuestro objetivo era aportar evidencias preclínicas in vivo para estas investigaciones, modelando el escenario LDE en nuevos modelos animales y demostrando que la combinación de inhibidores específicos de BCL2 o MYC con anti-CD20 puede mejorar la supervivencia a largo plazo en modelos animales de LDCBG-LDE. Para ello, primero generamos y caracterizamos tres modelos murinos transgénicos que recapitulan la compleja progresión y el microambiente tumoral característico del LDCBGDEL en ratón, replicando las clásicas alteraciones genéticas de estos pacientes mediante mutaciones condicionales que ocurren en etapas tempranas de la reacción de centro germinal. Además, demostramos que la transformación maligna de las células B de centro germinal dirigida por la expresión de NF-κB promueve la rápida co-expresión de BCL2 y MYC y reprime la apoptosis, acumulando inestabilidad genómica y sensibilizando a las células tumorales a la inhibición de BCL2 (con venetoclax) o de MYC (con MYCi975). Además, contribuimos con evidencias in vivo de que la combinación de venetoclax con inmunoterapia dirigida contra CD20 puede promover efectos sinérgicos contra las células tumorales del linfoma, mejorando la supervivencia de los ratones. No solo demostramos que esta sinergia incrementa la muerte de las células tumorales doble-expresantes de BCL2 y MYC en respuesta al tratamiento combinatorio, sino que también demostramos, por primera vez en LDCBG, que venetoclax promueve el enriquecimiento de las células T CD8+ efectoras activadas que infiltran el tumor, ejerciendo por tanto un papel inmunomodulador en el microambiente tumoral del LDCBG doble-expresante. También, demostramos que se acelera la linfomagénesis mediante la expresión forzada de MYC desde etapas tempranas de la reacción del centro germinal. Sin embargo, esta linfomagénesis estaba acompañada por la aparición de tumores gastrointestinales no derivados de células B, posiblemente debido a una activación inespecífica de la expresión de MYC, y que, por tanto, no responden a la inmunoterapia convencional anti-CD20 ni a un tratamiento antibiótico, empeorando por tanto la supervivencia de los ratones. En conjunto, nuestros resultados aportan tanto una prueba de concepto preclínica como una justificación de que incorporar venetoclax a los tratamientos basados en inmunoterapia frente a CD20 puede mejorar la respuesta en estos pacientes con LDCBGLDE. Además, aportamos nuevas evidencias para testar combinaciones con inhibidores de MYC, ya sea incorporándolos al tratamiento estándar actual R-CHOP o combinándolos con inhibidores específicos de BCL2, atacando así simultáneamente ambos talones de Aquiles del tumor. Estos ensayos preclínicos se pueden hacer tanto en nuestros modelos preclínicos como en la novedosa técnica de cultivo 3D que hemos implementado, que permite el cultivo a largo plazo de las células tumorales con su microambiente tumoral en forma de esferoides, pudiendo así hacer un cribado de nuevas estrategias terapéuticas ex vivo