Cell-type-specific role of CHK2 in mediating DNA damage-induced G2 cell cycle arrest

Cancer is a life-threatening disease that affects one in three people. Although most cases are sporadic, cancer risk can be increased by genetic factors. It remains unknown why certain genes predispose for specific forms of cancer only, such as checkpoint protein 2 (CHK2), in which gene mutations convey up to twofold higher risk for breast cancer but do not increase lung cancer risk. We have investigated the role of CHK2 and the related kinase checkpoint protein 1 (CHK1) in cell cycle regulation in primary breast and lung primary epithelial cells. At the molecular level, CHK1 activity was higher in lung cells, whereas CHK2 was more active in breast cells. Inhibition of CHK1 profoundly disrupted the cell cycle profile in both lung and breast cells, whereas breast cells were more sensitive toward inhibition of CHK2. Finally, we provide evidence that breast cells require CHK2 to induce a G2–M cell cycle arrest in response of DNA damage, whereas lung cells can partially compensate for the loss of CHK2. Our results provide an explanation as to why CHK2 germline mutations predispose for breast cancer but not for lung cancer

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Discrimination of the toxigenic dinoflagellate species Alexandrium tamarense and Alexandrium ostenfeldii in co-occurring natural populations from Scottish coastal waters

Blooms of the toxic dinoflagellate Alexandrium tamarense (Lebour) Balech, a known producer of potent neurotoxins associated with paralytic shellfish poisoning (PSP), are common annual events along the Scottish east coast. The co-occurrence of a second Alexandrium species, A. ostenfeldii (Paulsen) Balech & Tangen is reported in this study from waters of the Scottish east coast. The latter species has been suspected to be an alternative source of PSP toxins in northern Europe. Recent identification of toxic macrocyclic imines known as spirolides in A. ostenfeldii indicates a potential new challenge for monitoring toxic Alexandrium species and their respective toxins in natural populations. In mixed phytoplankton assemblages, Alexandrium species are dicult to discriminate accurately by conventional light microscopy. Species-specific rRNA probes based upon 18S and 28S ribosomal DNA sequences were developed for A. ostenfeldii and tested by dot-blot and fluorescence in situ hybridization (FISH) techniques. Hybridization patterns of A. ostenfeldii probes for cultured Alexandrium isolates, and cells from field populations from the Scottish east coast, were compared with those of rDNA probes for A. tamarense and a universal dinoflagellate probe. Alexandrium cell numbers in field samples determined by whole-cell in situ hybridization were much lower than those determined by optical microscopy with the Utermöhl method involving sedimentation chambers, but the results were highly correlated (e.g. r2=0.94; n=6 for A. tamarense). Determination of spirolides and PSP toxins by instrumental analysis on board ship demonstrated the presence of both toxi

Chromatin accessibility landscape of pediatric T-lymphoblastic leukemia and human T-cell precursors

We aimed at identifying the developmental stage at which leukemic cells of pediatric T-ALLs are arrested and at defining leukemogenic mechanisms based on ATAC-Seq. Chromatin accessibility maps of seven developmental stages of human healthy T cells revealed progressive chromatin condensation during T-cell maturation. Developmental stages were distinguished by 2,823 signature chromatin regions with 95% accuracy. Open chromatin surrounding SAE1 was identified to best distinguish thymic developmental stages suggesting a potential role of SUMOylation in T-cell development. Deconvolution using signature regions revealed that T-ALLs, including those with mature immunophenotypes, resemble the most immature populations, which was confirmed by TF-binding motif profiles. We integrated ATAC-Seq and RNA-Seq and found DAB1, a gene not related to leukemia previously, to be overexpressed, abnormally spliced and hyper-accessible in T-ALLs. DAB1-negative patients formed a distinct subgroup with particularly immature chromatin profiles and hyper-accessible binding sites for SPI1 (PU.1), a TF crucial for normal T-cell maturation. In conclusion, our analyses of chromatin accessibility and TF-binding motifs showed that pediatric T-ALL cells are most similar to immature thymic precursors, indicating an early developmental arrest

Inhibition of NGLY1 inactivates the transcription factor Nrf1 and potentiates proteasome inhibitor cytotoxicity

We discovered that the proteostasis modulating transcription factor Nrf1 requires cytosolic de-N-glycosylation by the N-glycanase NGly1 as part of its activation mechanism. Through a covalent small molecule library screen, we discovered an inhibitor of NGly1 that blocks Nrf1 activation in cells and potentiates the activity of proteasome inhibitor cancer drugs. The requirement of NGly1 for Nrf1 activity likely underlies several pathologies associated with a rare hereditary deficiency in NGly1

Identification of leukemic and pre-leukemic stem cells by clonal tracking from single-cell transcriptomics

Cancer stem cells drive disease progression and relapse in many types of cancer. Despite this, a thorough characterization of these cells remains elusive and with it the ability to eradicate cancer at its source. In acute myeloid leukemia (AML), leukemic stem cells (LSCs) underlie mortality but are difficult to isolate due to their low abundance and high similarity to healthy hematopoietic stem cells (HSCs). Here, we demonstrate that LSCs, HSCs, and pre-leukemic stem cells can be identified and molecularly profiled by combining single-cell transcriptomics with lineage tracing using both nuclear and mitochondrial somatic variants. While mutational status discriminates between healthy and cancerous cells, gene expression distinguishes stem cells and progenitor cell populations. Our approach enables the identification of LSC-specific gene expression programs and the characterization of differentiation blocks induced by leukemic mutations. Taken together, we demonstrate the power of single-cell multi-omic approaches in characterizing cancer stem cells.This project was financially supported by the Deutsche José Carreras Leukämie Stiftung grant DJCLS 20R/2017 (to L.V., S.H., L.M.S., and A.T.), the Emerson foundation grant 643577 (to L.V. and L.M.S.) and the German Bundesministerium für Bildung und Forschung (BMBF) through the Juniorverbund in der Systemmedizin “LeukoSyStem” (FKZ 01ZX1911D to L.V., S.H., and S.R). Contributions by S.R. were further supported by Emmy Noether Fellowship RA 3166/1-1 (DFG). Contributions by C.P. were supported by a Max-Eder Grant (German Cancer Aid 70111531). Contributions by D.N., J.C.J., W.K.H., and T.B. were supported by the Gutermuth Foundation, the H.W. & J. Hector fund, Baden-Württemberg, and the Dr. Rolf M. Schwiete Fund, Mannheim. D.N. is an endowed professor of the Deutsche José Carreras Leukämie Stiftung (DJCLS H 03/01