Cancer-associated DNA Hypermethylation of Polycomb Targets Requires DNMT3A Dual Recognition of Histone H2AK119 Ubiquitination and the Nucleosome Acidic Patch.

During tumor development, promoter CpG islands (CGIs) that are normally silenced by Polycomb repressive complexes (PRCs) become DNA hypermethylated. The molecular mechanism by which de novo DNA methyltransferase(s) catalyze CpG methylation at PRC-regulated regions remains unclear. Here we report a cryo-EM structure of the DNMT3A long isoform (DNMT3A1) N-terminal region in complex with a nucleosome carrying PRC1-mediated histone H2A lysine 119 monoubiquitination (H2AK119Ub). We identify regions within the DNMT3A1 N-terminus that bind H2AK119Ub and the nucleosome acidic patch. This bidentate interaction is required for effective DNMT3A1 engagement with H2AK119Ub-modified chromatin in cells. Furthermore, aberrant redistribution of DNMT3A1 to Polycomb target genes inhibits their transcriptional activation during cell differentiation and recapitulates the cancer-associated DNA hypermethylation signature. This effect is rescued by disruption of the DNMT3A1-acidic patch interaction. Together, our analyses reveal a binding interface critical for countering promoter CGI DNA hypermethylation, a major molecular hallmark of cancer.

Energy Funneling in a Noninteger Two-Dimensional Perovskite.

Energy funneling is a phenomenon that has been exploited in optoelectronic devices based on low-dimensional materials to improve their performance. Here, we introduce a new class of two-dimensional semiconductor, characterized by multiple regions of varying thickness in a single confined nanostructure with homogeneous composition. This "noninteger 2D semiconductor" was prepared via the structural transformation of two-octahedron-layer-thick (n = 2) 2D cesium lead bromide perovskite nanosheets; it consisted of a central n = 2 region surrounded by edge-lying n = 3 regions, as imaged by electron microscopy. Thicker noninteger 2D CsPbBr3 nanostructures were obtained as well. These noninteger 2D perovskites formed a laterally coupled quantum well band alignment with virtually no strain at the interface and no dielectric barrier, across which unprecedented intramaterial funneling of the photoexcitation energy was observed from the thin to the thick regions using time-resolved absorption and photoluminescence spectroscopy.

Size-Dependent Lattice Symmetry Breaking Determines the Exciton Fine Structure of Perovskite Nanocrystals.

The order of bright and dark excitonic states in lead-halide perovskite nanocrystals is debated. It has been proposed that the Rashba effect, driven by lattice-induced symmetry breaking, causes a bright excitonic ground state. Direct measurements of excitonic spectra, however, show the signatures of a dark ground state, bringing the role of the Rashba effect into question. We use an atomistic theory to model the exciton fine structure of perovskite nanocrystals, accounting for realistic lattice distortions. We calculate optical gaps and excitonic features that compare favorably with experimental works. The exciton fine structure splittings show a nonmonotonic size dependence due to a structural transition between cubic and orthorhombic phases. Additionally, the excitonic ground state is found to be dark with spin triplet character, exhibiting a small Rashba coupling. We additionally explore the effects of nanocrystal shape on the fine structure, clarifying observations on polydisperse nanocrystals.

Anomalous thickness dependence of photoluminescence quantum yield in black phosphorous.

Black phosphorus has emerged as a unique optoelectronic material, exhibiting tunable and high device performance from mid-infrared to visible wavelengths. Understanding the photophysics of this system is of interest to further advance device technologies based on it. Here we report the thickness dependence of the photoluminescence quantum yield at room temperature in black phosphorus while measuring the various radiative and non-radiative recombination rates. As the thickness decreases from bulk to ~4 nm, a drop in the photoluminescence quantum yield is initially observed due to enhanced surface carrier recombination, followed by an unexpectedly sharp increase in photoluminescence quantum yield with further thickness scaling, with an average value of ~30% for monolayers. This trend arises from the free-carrier to excitonic transition in black phosphorus thin films, and differs from the behaviour of conventional semiconductors, where photoluminescence quantum yield monotonically deteriorates with decreasing thickness. Furthermore, we find that the surface carrier recombination velocity of black phosphorus is two orders of magnitude lower than the lowest value reported in the literature for any semiconductor with or without passivation; this is due to the presence of self-terminated surface bonds in black phosphorus.

Simulations of nonradiative processes in semiconductor nanocrystals.

The description of carrier dynamics in spatially confined semiconductor nanocrystals (NCs), which have enhanced electron-hole and exciton-phonon interactions, is a great challenge for modern computational science. These NCs typically contain thousands of atoms and tens of thousands of valence electrons with discrete spectra at low excitation energies, similar to atoms and molecules, that converge to the continuum bulk limit at higher energies. Computational methods developed for molecules are limited to very small nanoclusters, and methods for bulk systems with periodic boundary conditions are not suitable due to the lack of translational symmetry in NCs. This perspective focuses on our recent efforts in developing a unified atomistic model based on the semiempirical pseudopotential approach, which is parameterized by first-principle calculations and validated against experimental measurements, to describe two of the main nonradiative relaxation processes of quantum confined excitons: exciton cooling and Auger recombination. We focus on the description of both electron-hole and exciton-phonon interactions in our approach and discuss the role of size, shape, and interfacing on the electronic properties and dynamics for II-VI and III-V semiconductor NCs.

Coronavirus Disease 2019 On Board a Submarine: A Retrospective Review.

BACKGROUND: The submarine environment presents unique challenges in mitigating the spread of respiratory viruses because of the re-circulatory atmosphere and lack of ability to physically distance. The atmosphere of a submarine is periodically ventilated and continuously scrubbed. However, the air is recycled for months until the ship is able to ventilate. An outbreak of coronavirus disease 2019 (COVID-19) occurred on a U.S. Navy fast-attack nuclear submarine (SSN) with a crew of 128 personnel. METHODS: Demographics, symptom data, and test results for all crew members on board during the outbreak were collected. Testing was completed by real-time reverse-transcriptase polymerase chain reaction, and symptom data were collected via a patient-reported online application. Symptom results were collected from August 4, 2020 to September 1, 2020. RESULTS: The crew was 100% male, with a mean age of 27.0 years. All crew members met the stringent medical standards for submarine and sea duty. Fifty-five Sailors tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (43.0% of the crew) during the outbreak. Additionally, nine Sailors (7.0% of the crew) met the criteria for infection despite testing negative, resulting in an overall attack rate of 50.0%. Among the 64 crew members with suspected or confirmed COVID-19, 1 (1.6%) was hospitalized. There were no deaths. Out of the 55 positive tests, there were 6 (10.9%) asymptomatic positive cases. CONCLUSIONS: As expected, SARS-CoV-2 was able to spread rapidly among a submarine crew. In 11 days, the infection spread to 64 total crewmembers out of 128. Outbreaks such as these have played a role in future COVID-19 testing and mitigation protocols that have affected day-to-day operations.

H3K36 dimethylation shapes the epigenetic interaction landscape by directing repressive chromatin modifications in embryonic stem cells.

Epigenetic modifications on the chromatin do not occur in isolation. Chromatin-associated proteins and their modification products form a highly interconnected network, and disturbing one component may rearrange the entire system. We see this increasingly clearly in epigenetically dysregulated cancers. It is important to understand the rules governing epigenetic interactions. Here, we use the mouse embryonic stem cell (mESC) model to describe in detail the relationships within the H3K27-H3K36-DNA methylation subnetwork. In particular, we focus on the major epigenetic reorganization caused by deletion of the histone 3 lysine 36 methyltransferase NSD1, which in mESCs deposits nearly all of the intergenic H3K36me2. Although disturbing the H3K27 and DNA methylation (DNAme) components also affects this network to a certain extent, the removal of H3K36me2 has the most drastic effect on the epigenetic landscape, resulting in full intergenic spread of H3K27me3 and a substantial decrease in DNAme. By profiling DNMT3A and CHH methylation (mCHH), we show that H3K36me2 loss upon Nsd1-KO leads to a massive redistribution of DNMT3A and mCHH away from intergenic regions and toward active gene bodies, suggesting that DNAme reduction is at least in part caused by redistribution of de novo methylation. Additionally, we show that pervasive acetylation of H3K27 is regulated by the interplay of H3K36 and H3K27 methylation. Our analysis highlights the importance of H3K36me2 as a major determinant of the developmental epigenome and provides a framework for further consolidating our knowledge of epigenetic networks.

Two competing mechanisms of DNMT3A recruitment regulate the dynamics of de novo DNA methylation at PRC1-targeted CpG islands.

Precise deposition of CpG methylation is critical for mammalian development and tissue homeostasis and is often dysregulated in human diseases. The localization of de novo DNA methyltransferase DNMT3A is facilitated by its PWWP domain recognizing histone H3 lysine 36 (H3K36) methylation1,2 and is normally depleted at CpG islands (CGIs)3. However, methylation of CGIs regulated by Polycomb repressive complexes (PRCs) has also been observed4-8. Here, we report that DNMT3A PWWP domain mutations identified in paragangliomas9 and microcephalic dwarfism10 promote aberrant localization of DNMT3A to CGIs in a PRC1-dependent manner. DNMT3A PWWP mutants accumulate at regions containing PRC1-mediated formation of monoubiquitylated histone H2A lysine 119 (H2AK119ub), irrespective of the amounts of PRC2-catalyzed formation of trimethylated histone H3 lysine 27 (H3K27me3). DNMT3A interacts with H2AK119ub-modified nucleosomes through a putative amino-terminal ubiquitin-dependent recruitment region, providing an alternative form of DNMT3A genomic targeting that is augmented by the loss of PWWP reader function. Ablation of PRC1 abrogates localization of DNMT3A PWWP mutants to CGIs and prevents aberrant DNA hypermethylation. Our study implies that a balance between DNMT3A recruitment by distinct reader domains guides de novo CpG methylation and may underlie the abnormal DNA methylation landscapes observed in select human cancer subtypes and developmental disorders.

Depletion of H3K36me2 recapitulates epigenomic and phenotypic changes induced by the H3.3K36M oncohistone mutation.

Hotspot histone H3 mutations have emerged as drivers of oncogenesis in cancers of multiple lineages. Specifically, H3 lysine 36 to methionine (H3K36M) mutations are recurrently identified in chondroblastomas, undifferentiated sarcomas, and head and neck cancers. While the mutation reduces global levels of both H3K36 dimethylation (H3K36me2) and trimethylation (H3K36me3) by dominantly inhibiting their respective specific methyltransferases, the relative contribution of these methylation states to the chromatin and phenotypic changes associated with H3K36M remains unclear. Here, we specifically deplete H3K36me2 or H3K36me3 in mesenchymal cells, using CRISPR-Cas9 to separately knock out the corresponding methyltransferases NSD1/2 or SETD2. By profiling and comparing the epigenomic and transcriptomic landscapes of these cells with cells expressing the H3.3K36M oncohistone, we find that the loss of H3K36me2 could largely recapitulate H3.3K36M's effect on redistribution of H3K27 trimethylation (H3K27me3) and gene expression. Consistently, knockout of Nsd1/2, but not Setd2, phenocopies the differentiation blockade and hypersensitivity to the DNA-hypomethylating agent induced by H3K36M. Together, our results support a functional divergence between H3K36me2 and H3K36me3 and their nonredundant roles in H3K36M-driven oncogenesis.

Uncovering the Role of Hole Traps in Promoting Hole Transfer from Multiexcitonic Quantum Dots to Molecular Acceptors.

Understanding electronic dynamics in multiexcitonic quantum dots (QDs) is important for designing efficient systems useful in high power scenarios, such as solar concentrators and multielectron charge transfer. The multiple charge carriers within a QD can undergo undesired Auger recombination events, which rapidly annihilate carriers on picosecond time scales and generate heat from absorbed photons instead of useful work. Compared to the transfer of multiple electrons, the transfer of multiple holes has proven to be more difficult due to slower hole transfer rates. To probe the competition between Auger recombination and hole transfer in CdSe, CdS, and CdSe/CdS QDs of varying sizes, we synthesized a phenothiazine derivative with optimized functionalities for binding to QDs as a hole accepting ligand and for spectroscopic observation of hole transfer. Transient absorption spectroscopy was used to monitor the photoinduced absorption features from both trapped holes and oxidized ligands under excitation fluences where the averaged initial number of excitons in a QD ranged from ∼1 to 19. We observed fluence-dependent hole transfer kinetics that last around 100 ps longer than the predicted Auger recombination lifetimes, and the transfer of up to 3 holes per QD. Theoretical modeling of the kinetics suggests that binding of hole acceptors introduces trapping states significantly different from those in native QDs passivated with oleate ligands. Holes in these modified trap states have prolonged lifetimes, which promotes the hole transfer efficiency. These results highlight the beneficial role of hole-trapping states in devising hole transfer pathways in QD-based systems under multiexcitonic conditions.

Histone H3.3 G34 mutations promote aberrant PRC2 activity and drive tumor progression.

A high percentage of pediatric gliomas and bone tumors reportedly harbor missense mutations at glycine 34 in genes encoding histone variant H3.3. We find that these H3.3 G34 mutations directly alter the enhancer chromatin landscape of mesenchymal stem cells by impeding methylation at lysine 36 on histone H3 (H3K36) by SETD2, but not by the NSD1/2 enzymes. The reduction of H3K36 methylation by G34 mutations promotes an aberrant gain of PRC2-mediated H3K27me2/3 and loss of H3K27ac at active enhancers containing SETD2 activity. This altered histone modification profile promotes a unique gene expression profile that supports enhanced tumor development in vivo. Our findings are mirrored in G34W-containing giant cell tumors of bone where patient-derived stromal cells exhibit gene expression profiles associated with early osteoblastic differentiation. Overall, we demonstrate that H3.3 G34 oncohistones selectively promote PRC2 activity by interfering with SETD2-mediated H3K36 methylation. We propose that PRC2-mediated silencing of enhancers involved in cell differentiation represents a potential mechanism by which H3.3 G34 mutations drive these tumors.

PRC2 engages a bivalent H3K27M-H3K27me3 dinucleosome inhibitor.

A lysine-to-methionine mutation at lysine 27 of histone 3 (H3K27M) has been shown to promote oncogenesis in a subset of pediatric gliomas. While there is evidence that this "oncohistone" mutation acts by inhibiting the histone methyltransferase PRC2, the details of this proposed mechanism nevertheless continue to be debated. Recent evidence suggests that PRC2 must simultaneously bind both H3K27M and H3K27me3 to experience competitive inhibition of its methyltransferase activity. In this work, we used PRC2 inhibitor treatments in a transgenic H3K27M cell line to validate this dependence in a cellular context. We further used designer chromatin inhibitors to probe the geometric constraints of PRC2 engagement of H3K27M and H3K27me3 in a biochemical setting. We found that PRC2 binds to a bivalent inhibitor unit consisting of an H3K27M and an H3K27me3 nucleosome and exhibits a distance dependence in its affinity for such an inhibitor, which favors closer proximity of the 2 nucleosomes within a chromatin array. Together, our data precisely delineate fundamental aspects of the H3K27M inhibitor and support a model wherein PRC2 becomes trapped at H3K27M-H3K27me3 boundaries.

The histone mark H3K36me2 recruits DNMT3A and shapes the intergenic DNA methylation landscape.

Enzymes that catalyse CpG methylation in DNA, including the DNA methyltransferases 1 (DNMT1), 3A (DNMT3A) and 3B (DNMT3B), are indispensable for mammalian tissue development and homeostasis1-4. They are also implicated in human developmental disorders and cancers5-8, supporting the critical role of DNA methylation in the specification and maintenance of cell fate. Previous studies have suggested that post-translational modifications of histones are involved in specifying patterns of DNA methyltransferase localization and DNA methylation at promoters and actively transcribed gene bodies9-11. However, the mechanisms that control the establishment and maintenance of intergenic DNA methylation remain poorly understood. Tatton-Brown-Rahman syndrome (TBRS) is a childhood overgrowth disorder that is defined by germline mutations in DNMT3A. TBRS shares clinical features with Sotos syndrome (which is caused by haploinsufficiency of NSD1, a histone methyltransferase that catalyses the dimethylation of histone H3 at K36 (H3K36me2)8,12,13), which suggests that there is a mechanistic link between these two diseases. Here we report that NSD1-mediated H3K36me2 is required for the recruitment of DNMT3A and maintenance of DNA methylation at intergenic regions. Genome-wide analysis shows that the binding and activity of DNMT3A colocalize with H3K36me2 at non-coding regions of euchromatin. Genetic ablation of Nsd1 and its paralogue Nsd2 in mouse cells results in a redistribution of DNMT3A to H3K36me3-modified gene bodies and a reduction in the methylation of intergenic DNA. Blood samples from patients with Sotos syndrome and NSD1-mutant tumours also exhibit hypomethylation of intergenic DNA. The PWWP domain of DNMT3A shows dual recognition of H3K36me2 and H3K36me3 in vitro, with a higher binding affinity towards H3K36me2 that is abrogated by TBRS-derived missense mutations. Together, our study reveals a trans-chromatin regulatory pathway that connects aberrant intergenic CpG methylation to human neoplastic and developmental overgrowth.

Metal-organic frameworks tailor the properties of aluminum nanocrystals.

Metal-organic frameworks (MOFs) and metal nanoparticles are two classes of materials that have received considerable recent attention, each for controlling chemical reactivities, albeit in very different ways. Here, we report the growth of MOF shell layers surrounding aluminum nanocrystals (Al NCs), an Earth-abundant metal with energetic, plasmonic, and photocatalytic properties. The MOF shell growth proceeds by means of dissolution-and-growth chemistry that uses the intrinsic surface oxide of the NC to obtain the Al3+ ions accommodated into the MOF nodes. Changes in the Al NC plasmon resonance provide an intrinsic optical probe of its dissolution and growth kinetics. This same chemistry enables a highly controlled oxidation of the Al NCs, providing a precise method for reducing NC size in a shape-preserving manner. The MOF shell encapsulation of the Al NCs results in increased efficiencies for plasmon-enhanced photocatalysis, which is observed for the hydrogen-deuterium exchange and reverse water-gas shift reactions.

Vulvar Cancer.

This article reviews the epidemiology, diagnosis, and management of vulvar preinvasive lesions, squamous cell carcinoma, and melanoma. There is an emphasis on sentinel lymph node dissection for early stage disease and advances in chemoradiation for late-stage disease. A brief review of vulvar Paget disease is also included.

Safety of laparoscopic sacrocolpopexy with concurrent rectopexy: peri-operative morbidity in a nationwide cohort.

INTRODUCTION AND HYPOTHESIS: Rectopexy and sacrocolpopexy can be performed concurrently to treat rectal and vaginal prolapse. We hypothesized that concurrent procedures might be associated with more complications than rectopexy and sacrocolpopexy alone. METHODS: Patients undergoing laparoscopic sacrocolpopexy or rectopexy, or concurrent laparoscopic sacrocolpopexy and rectopexy were identified in the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database from 2013 to 2016. Preoperative characteristics, operative time, and 30-day post-operative complications were compared between groups. Complications were those defined by the ACS Risk Calculator. Descriptive tests and regression methods were utilized for group comparisons. Significance was set at p < 0.05. RESULTS: We identified 7,232 laparoscopic sacrocolpopexy, 1,560 laparoscopic rectopexy, and 123 concurrent laparoscopic sacrocolpopexy and rectopexy cases. Patients undergoing concurrent procedures were more commonly white, non-Hispanic, non-diabetic, and smokers. Operative time was longest for concurrent procedures, followed by sacrocolpopexy and rectopexy (p < 0.0001). Patients undergoing isolated rectopexy were more commonly ≥ American Society of Anesthesiologists class 3 (p < 0.0001). Rates of any complication for colpopexy, rectopexy, and concurrent procedures did not differ (6.18%, 7.63%, 8.94%; p = 0.058). Serious complication rates for colpopexy, rectopexy, and concurrent procedures did not differ (5.52%, 6.35%, 8.13%; p = 0.222). Odds of experiencing any complication were higher comparing rectopexy with colpopexy alone (adjusted odds ratio = 1.252, 95% CI 1.002-1.565). Comparing all groups, rectopexy had the highest mortality, reoperation, and transfusion rates (all p < 0.05). Concurrent procedures had the highest surgical site and urinary tract infection rates (all p < 0.05). CONCLUSIONS: Complications were low for all three procedures. Concurrent repair may be appropriate in well-selected patients.

Effect of ibuprofen vs acetaminophen on postpartum hypertension in preeclampsia with severe features: a double-masked, randomized controlled trial.

BACKGROUND: Nonsteroidal antiinflammatory drug use has been shown to increase blood pressure in nonpregnant adults. Because of this, the American College of Obstetricians and Gynecologists suggests avoiding their use in women with postpartum hypertension; however, evidence to support this recommendation is lacking. OBJECTIVE: Our goal was to test the hypothesis that nonsteroidal antiinflammatory drugs, such as ibuprofen, adversely affect postpartum blood pressure control in women with preeclampsia with severe features. STUDY DESIGN: At delivery, we randomized women with preeclampsia with severe features to receive around-the-clock oral dosing with either 600 mg of ibuprofen or 650 mg of acetaminophen every 6 hours. Dosing began within 6 hours after delivery and continued until discharge, with opioid analgesics available as needed for breakthrough pain. Study drugs were encapsulated in identical capsules such that patients, nurses, and physicians were masked to study allocation. Exclusion criteria were serum aspartate aminotransferase or alanine aminotransferase >200 mg/dL, serum creatinine >1.0 mg/dL, infectious hepatitis, gastroesophageal reflux disease, age <18 years, or current incarceration. Our primary outcome was the duration of severe-range hypertension, defined as the time (in hours) from delivery to the last blood pressure ≥160/110 mm Hg. Secondary outcomes were time from delivery to last blood pressure ≥150/100 mm Hg, mean arterial pressure, need for antihypertensive medication at discharge, prolongation of hospital stay for blood pressure control, postpartum use of short-acting antihypertensives for acute blood pressure control, and opioid use for breakthrough pain. We analyzed all outcome data according to intention-to-treat principles. RESULTS: We assessed 154 women for eligibility, of whom 100 met entry criteria, agreed to participate, and were randomized to receive postpartum ibuprofen or acetaminophen for first-line pain control. Seven patients crossed over or did not receive their allocated study drug, and 93 completed the study protocol in their assigned groups. We found no differences in baseline characteristics between groups, including mode of delivery, body mass index, parity, race, chronic hypertension, and maximum blood pressure prior to delivery. We did not find a difference in the duration of severe-range hypertension in the ibuprofen vs acetaminophen groups (35.3 vs 38.0 hours, P = .30). There were no differences between groups in the secondary outcome measures of time from delivery to last blood pressure ≥150/100 mm Hg, postpartum mean arterial pressure, maximum postpartum systolic or diastolic blood pressures, any postpartum blood pressure ≥160/110 mm Hg, short-acting antihypertensive use for acute blood pressure control, length of postpartum stay, need to extend postpartum stay for blood pressure control, antihypertensive use at discharge, or opioid use for inadequate pain control. In a subgroup analysis of patients who experienced severe-range hypertension, the mean time to blood pressure control in the acetaminophen group was 68.4 hours and ibuprofen group was 56.7 hours (P = .26). At 6 weeks postpartum, there were no differences between groups in the rates of obstetric triage visits, hospital readmissions, continued opioid use, or continued antihypertensive use. CONCLUSION: The first-line use of ibuprofen rather than acetaminophen for postpartum pain did not lengthen the duration of severe-range hypertension in women with preeclampsia with severe features.