Distinct and overlapping RNA determinants for binding and target-primed reverse transcription by Bombyx mori R2 retrotransposon protein.

Eukaryotic retrotransposons encode a reverse transcriptase that binds RNA to template DNA synthesis. The ancestral non-long terminal repeat (non-LTR) retrotransposons encode a protein that performs target-primed reverse transcription (TPRT), in which the nicked genomic target site initiates complementary DNA (cDNA) synthesis directly into the genome. The best understood model system for biochemical studies of TPRT is the R2 protein from the silk moth Bombyx mori. The R2 protein selectively binds the 3' untranslated region of its encoding RNA as template for DNA insertion to its target site in 28S ribosomal DNA. Here, binding and TPRT assays define RNA contributions to RNA-protein interaction, template use for TPRT and the fidelity of template positioning for TPRT cDNA synthesis. We quantify both sequence and structure contributions to protein-RNA interaction. RNA determinants of binding affinity overlap but are not equivalent to RNA features required for TPRT and its fidelity of template positioning for full-length TPRT cDNA synthesis. Additionally, we show that a previously implicated RNA-binding protein surface of R2 protein makes RNA binding affinity dependent on the presence of two stem-loops. Our findings inform evolutionary relationships across R2 retrotransposon RNAs and are a step toward understanding the mechanism and template specificity of non-LTR retrotransposon mobility.

The cell adhesion molecule Echinoid promotes tissue survival and separately restricts tissue overgrowth in Drosophila imaginal discs.

The interactions that cells in Drosophila imaginal discs have with their neighbors are known to regulate their ability to survive. In a screen of genes encoding cell surface proteins for gene knockdowns that affect the size or shape of mutant clones, we found that clones of cells with reduced levels of echinoid (ed) are fewer, smaller, and can be eliminated during development. In contrast, discs composed mostly of ed mutant tissue are overgrown. We find that ed mutant tissue has lower levels of the anti-apoptotic protein Diap1 and has increased levels of apoptosis which is consistent with the observed underrepresentation of ed mutant clones and the slow growth of ed mutant tissue. The eventual overgrowth of ed mutant tissue results not from accelerated growth, but from prolonged growth resulting from a failure to arrest growth at the appropriate final size. Ed has previously been shown to physically interact with multiple Hippo-pathway components and it has been proposed to promote Hippo pathway signaling, to exclude Yorkie (Yki) from the nucleus, and restrain the expression of Yki-target genes. We did not observe changes in Yki localization in ed mutant tissue and found decreased levels of expression of several Yorkie-target genes, findings inconsistent with the proposed effect of Ed on Yki. We did, however, observe increased expression of several Yki-target genes in wild-type cells neighboring ed mutant cells, which may contribute to elimination of ed mutant clones. Thus, ed has two distinct functions: an anti-apoptotic function by maintaining Diap1 levels, and a function to arrest growth at the appropriate final size. Both of these are unlikely to be explained by a simple effect on the Hippo pathway.

Scaled-Up Synthesis of Freestanding Molybdenum Disulfide Membranes for Nanopore Sensing.

2D materials are ideal for nanopores with optimal detection sensitivity and resolution. Among these, molybdenum disulfide (MoS2 ) has gained traction as a less hydrophobic material than graphene. However, experiments using 2D nanopores remain challenging due to the lack of scalable methods for high-quality freestanding membranes. Herein, a site-directed, scaled-up synthesis of MoS2 membranes on predrilled nanoapertures on 4-inch wafer substrates with 75% yields is reported. Chemical vapor deposition (CVD), which introduces sulfur and molybdenum dioxide vapors across the sub-100 nm nanoapertures results in exclusive formation of freestanding membranes that seal the apertures. Nucleation and growth near the nanoaperture edges is followed by nanoaperture decoration with MoS2 , which proceeds until a critical flake curvature is achieved, after which fully spanning freestanding membranes form. Intentional blocking of reagent flow through the apertures inhibits MoS2 nucleation around the nanoapertures, promoting the formation of large-crystal monolayer MoS2 membranes. The in situ grown membranes along with facile membrane wetting and nanopore formation using dielectric breakdown enables the recording of dsDNA translocation events at an unprecedentedly high 1 MHz bandwidth. The methods presented here are important steps toward the development of scalable single-layer membrane manufacture for 2D nanofluidics and nanopore applications.

Time- and Species-Dependent Bacterial Adhesion to Titanium over Short Exposure Periods: An In Vitro Study.

A considerable percentage of dental implant patients experience biofilm-mediated peri-implant disease following transmucosal abutment application. Bacterial adhesion is an early step in biofilm development. Our purpose was to assess adhesion of specific bacterial species to titanium over short exposure periods. Eight bacterial species were selected for this analysis: Streptococcus oralis, Streptococcus mitis, Gemella haemolysans, Streptococcus gordonii, Streptococcus sanguinis, Neisseria flavescens, Streptococcus salivarius, and Pseudomonas aeruginosa. We cultured each species with appropriate media and exposed titanium foil discs to the bacteria for 60, 15, 5, 1, or 0.25 minutes. Optical density at 600-nm wavelength (OD600) was assessed for the baseline inoculum and each species/exposure combination. The proportion of bacteria adherent to titanium was determined for each experimental condition. Striking titanium adhesion was noted for all evaluated species even when exposure time was limited to 15 seconds. Strategies to limit bacterial adhesion at dental implant surfaces may offer potential for improved treatment outcomes and preservation of peri-implant health.

Cerebral vasculopathy and strokes in a child with COVID-19 antibodies: illustrative case.

BACKGROUND: The ability of coronavirus disease 2019 (COVID-19) to cause neurological insults in afflicted adults is becoming increasingly understood by way of an ever-growing amount of international data. By contrast, the pandemic illness's neurological effects in the pediatric population are both poorly understood and sparsely reported. OBSERVATIONS: In this case, the authors reported their experience with a preschool-age child with hydrocephalus who suffered multiterritory strokes presumed secondary to immune-mediated cerebral vasculopathy as a result of asymptomatic COVID-19 infection. LESSONS: Growing evidence indicates that COVID-19 can cause neurological sequelae such as encephalitis and strokes. In this case report, the authors discussed a case of cerebral vasculopathy and strokes in a pediatric patient who was positive for COVID-19.

Utilizing the Regional Acceleratory Phenomenon and Dental Implant Anchorage for Distalization and Intrusion of a Mesially Tipped Mandibular Molar: A Case Report.

INTRODUCTION: Introduction of a surgical insult in conjunction with orthodontic therapy has been shown to accelerate treatment in minor tooth movement and comprehensive orthodontic cases by induction of the regional acceleratory phenomenon (RAP). When applying this concept to a molar tipped into an adjacent edentulous site, a dental implant can be planned to anchor the movement. CASE PRESENTATION: A generally and periodontally healthy 25-year-old patient presented missing tooth #19, with tooth #18 mesially tipped into the first molar crown space. A dental implant was placed in the #19 position. Following osseointegration, the implant anchored orthodontic movement of the adjacent tooth, which was initiated in conjunction with third molar extraction. CONCLUSION: Favorable biomechanics for molar uprighting can be achieved using an osseointegrated implant and a customized orthodontic device. The presented technique facilitates implant site development without delaying placement of the fixture and simplifies fabrication of a harmonious and anatomic implant-supported restoration. Induction of the RAP may hasten treatment completion.

FXR1 splicing is important for muscle development and biomolecular condensates in muscle cells.

Fragile-X mental retardation autosomal homologue-1 (FXR1) is a muscle-enriched RNA-binding protein. FXR1 depletion is perinatally lethal in mice, Xenopus, and zebrafish; however, the mechanisms driving these phenotypes remain unclear. The FXR1 gene undergoes alternative splicing, producing multiple protein isoforms and mis-splicing has been implicated in disease. Furthermore, mutations that cause frameshifts in muscle-specific isoforms result in congenital multi-minicore myopathy. We observed that FXR1 alternative splicing is pronounced in the serine- and arginine-rich intrinsically disordered domain; these domains are known to promote biomolecular condensation. Here, we show that tissue-specific splicing of fxr1 is required for Xenopus development and alters the disordered domain of FXR1. FXR1 isoforms vary in the formation of RNA-dependent biomolecular condensates in cells and in vitro. This work shows that regulation of tissue-specific splicing can influence FXR1 condensates in muscle development and how mis-splicing promotes disease.

Beyond observation: Protocols and capabilities of an Emergency Department Observation Unit.

OBJECTIVE: Emergency Department Observation Units (Obs Units) provide a setting and a mechanism for further care of Emergency Department (ED) patients. Our hospital has a protocol-driven, type 1, complex 20 bed Obs Unit with 36 different protocols. We wanted to understand how the different protocols performed and what types of care were provided. METHODS: This was an IRB-approved, retrospective chart review study. A random 10% of ED patient charts with a "transfer to observation" order were selected monthly from October 2015 through June 2017. This database was designed to identify high and low functioning protocols based on length of stays (LOS) and admission rates. RESULTS: Over 20 months, a total of 984 patients qualified for the study. The average age was 49.5 ±â€¯17.2 years, 57.3% were women, and 32.3% were non-Caucasian. The admission rate was 23.5% with an average LOS in observation of 13.7 h [95% CI 13.3-14.1]. Thirty day return rate was 16.8% with 5.3% of the patients returning to the ED within the first 72 h. Thirty six different protocols were used, with the most common being chest pain (13.9%) and general (13.2%). Almost 70% received a consultation from another service, and 7.2% required a procedure while in observation. Procedures included fluoroscopic-guided lumbar punctures, endoscopies, dental extractions, and catheter replacements (nephrostomy, gastrostomy, and biliary tubes). CONCLUSIONS: An Obs Unit can care for a wide variety of patients who require multiple consultations, procedures, and care coordination while maintaining an acceptable length of stay and admission rate.

An Emergency Department Observation Unit Is a Feasible Setting for Multidisciplinary Geriatric Assessments in Compliance With the Geriatric Emergency Department Guidelines.

BACKGROUND: The Geriatric Emergency Department (ED) Guidelines recommend providing multidisciplinary geriatric assessment in the ED, but these assessments can be difficult to coordinate and may prolong length of stay. Patients who need longer than a typical ED stay can be placed in an ED observation unit (Obs Unit). We investigated the effects of offering multidisciplinary assessments for ED patients in an Obs Unit. METHODS: Evaluation by a geriatric hospital consultation team, physical therapist, case manager, and/or pharmacist was made available to all Obs Unit patients. Use of any or all of these ancillary consult services could be requested by the Obs Unit physician. A retrospective chart review of random older adult Obs Unit patients was done to assess rates of consult use and interventions by these consulting teams. All patients ≥ 65 years old in our institutional review board-approved, monthly Obs Unit quality database from October 2015 through March 2017 were included. RESULTS: Our quality database included 221 older patients over 18 months. The mean (±SD) age was 73.3 (±6.8) years (range = 65-96 years) and 55.2% were women. The mean (±SD) observation length of stay was 14.7 (±6.5) hours. The majority (74.3%) were discharged from the Obs Unit and 72-hour ED recidivism was 3.6%. Overall, at least one of the multidisciplinary consultant services were requested in 40.3% of patients (n = 89). Additional interventions or services were recommended in 80.0% of patients evaluated by physical therapy (32 of 40 patients), 100% of those evaluated by a pharmacist (five of five patients), 38% of those evaluated by case management (27 of 71 patients), and 100% of those evaluated by a geriatrician (eight of eight patients). Only 5.4% (n = 12) of patients were placed in observation specifically for multidisciplinary assessment; these patients had a mean (±SD) length of stay of 12.2 (±5) hours and an admission rate of 41.7%. CONCLUSIONS: Incorporating elements of multidisciplinary geriatric assessment for older patients is feasible within an observation time frame and resulted in targeted interventions. An Obs Unit is a reasonable setting to offer services in compliance with the Geriatric ED Guidelines.

Tunable and laser-reconfigurable 2D heterocrystals obtained by epitaxial stacking of crystallographically incommensurate Bi2Se3 and MoS2 atomic layers.

Vertical stacking is widely viewed as a promising approach for designing advanced functionalities using two-dimensional (2D) materials. Combining crystallographically commensurate materials in these 2D stacks has been shown to result in rich new electronic structure, magnetotransport, and optical properties. In this context, vertical stacks of crystallographically incommensurate 2D materials with well-defined crystallographic order are a counterintuitive concept and, hence, fundamentally intriguing. We show that crystallographically dissimilar and incommensurate atomically thin MoS2 and Bi2Se3 layers can form rotationally aligned stacks with long-range crystallographic order. Our first-principles theoretical modeling predicts heterocrystal electronic band structures, which are quite distinct from those of the parent crystals, characterized with an indirect bandgap. Experiments reveal striking optical changes when Bi2Se3 is stacked layer by layer on monolayer MoS2, including 100% photoluminescence (PL) suppression, tunable transmittance edge (1.1→0.75 eV), suppressed Raman, and wide-band evolution of spectral transmittance. Disrupting the interface using a focused laser results in a marked the reversal of PL, Raman, and transmittance, demonstrating for the first time that in situ manipulation of interfaces can enable "reconfigurable" 2D materials. We demonstrate submicrometer resolution, "laser-drawing" and "bit-writing," and novel laser-induced broadband light emission in these heterocrystal sheets.

Atomically thin layers of B-N-C-O with tunable composition.

In recent times, atomically thin alloys of boron, nitrogen, and carbon have generated significant excitement as a composition-tunable two-dimensional (2D) material that demonstrates rich physics as well as application potentials. The possibility of tunably incorporating oxygen, a group VI element, into the honeycomb sp(2)-type 2D-BNC lattice is an intriguing idea from both fundamental and applied perspectives. We present the first report on an atomically thin quaternary alloy of boron, nitrogen, carbon, and oxygen (2D-BNCO). Our experiments suggest, and density functional theory (DFT) calculations corroborate, stable configurations of a honeycomb 2D-BNCO lattice. We observe micrometer-scale 2D-BNCO domains within a graphene-rich 2D-BNC matrix, and are able to control the area coverage and relative composition of these domains by varying the oxygen content in the growth setup. Macroscopic samples comprising 2D-BNCO domains in a graphene-rich 2D-BNC matrix show graphene-like gate-modulated electronic transport with mobility exceeding 500 cm(2) V(-1) s(-1), and Arrhenius-like activated temperature dependence. Spin-polarized DFT calculations for nanoscale 2D-BNCO patches predict magnetic ground states originating from the B atoms closest to the O atoms and sizable (0.6 eV < E g < 0.8 eV) band gaps in their density of states. These results suggest that 2D-BNCO with novel electronic and magnetic properties have great potential for nanoelectronics and spintronic applications in an atomically thin platform.

Chemical Vapor Deposition Synthesized Atomically Thin Molybdenum Disulfide with Optoelectronic-Grade Crystalline Quality.

The ability to synthesize high-quality samples over large areas and at low cost is one of the biggest challenges during the developmental stage of any novel material. While chemical vapor deposition (CVD) methods provide a promising low-cost route for CMOS compatible, large-scale growth of materials, it often falls short of the high-quality demands in nanoelectronics and optoelectronics. We present large-scale CVD synthesis of single- and few-layered MoS2 using direct vapor-phase sulfurization of MoO2, which enables us to obtain extremely high-quality single-crystal monolayer MoS2 samples with field-effect mobility exceeding 30 cm(2)/(V s) in monolayers. These samples can be readily synthesized on a variety of substrates, and demonstrate a high-degree of optoelectronic uniformity in Raman and photoluminescence mapping over entire crystals with areas exceeding hundreds of square micrometers. Because of their high crystalline quality, Raman spectroscopy on these samples reveal a range of multiphonon processes through peaks with equal or better clarity compared to past reports on mechanically exfoliated samples. This enables us to investigate the layer thickness and substrate dependence of the extremely weak phonon processes at 285 and 487 cm(-1) in 2D-MoS2. The ultrahigh, optoelectronic-grade crystalline quality of these samples could be further established through photocurrent spectroscopy, which clearly reveal excitonic states at room temperature, a feat that has been previously demonstrated only on samples which were fabricated by micro-mechanical exfoliation and then artificially suspended across trenches. Our method reflects a big step in the development of atomically thin, 2D-MoS2 for scalable, high-quality optoelectronics.

The changing colors of a quantum-confined topological insulator.

Bismuth selenide (Bi2Se3) is a 3D topological insulator, its strong spin-orbit coupling resulting in the well-known topologically protected coexistence of gapless metallic surface states and semiconducting bulk states with a band gap, Eg ≃ 300 meV. A fundamental question of considerable importance is how the electronic properties of this material evolve under nanoscale confinement. We report on catalyst-free, high-quality single-crystalline Bi2Se3 with controlled lateral sizes and layer thicknesses that could be tailored down to a few nanometers and a few quintuple layers (QLs), respectively. Energy-resolved photoabsorption spectroscopy (1.5 eV < E(photon) < 6 eV) of these samples reveals a dramatic evolution of the photon absorption spectra as a function of size, transitioning from a featureless metal-like spectrum in the bulk (corresponding to a visually gray color), to one with a remarkably large band gap (Eg ≥ 2.5 eV) and a spectral shape that correspond to orange-red colorations in the smallest samples, similar to those seen in semiconductor nanostructures. We analyze this colorful transition using ab initio density functional theory and tight-binding calculations which corroborate our experimental findings and further suggest that while purely 2D sheets of few QL-thick Bi2Se3 do exhibit small band gaps that are consistent with previous ARPES results, the presently observed large gaps of a few electronvolts can only result from a combined effect of confinement in all three directions.

Effects of structural and electronic characteristics of chalcones on the activation of peroxisome proliferator-activated receptor gamma.

Chalcones share some structural similarities with GW-1929, a highly-selective and potent agonist for peroxisome proliferator-activated receptor-gamma (PPARγ). In this study, we tested 53 structurally diverse chalcones to identify characteristics essential for PPARγ activation in a GAL4-based transactivation assay. This screen identified several novel chalcone agonists of PPARγ. Our results indicate that chalcones with an electron rich group or sterically large groups such as naphthyl on the carbonyl side tend to activate PPARγ. The absence of any strict structural or electronic requirements suggests that the flexibility of the PPARγ ligand binding pocket may allow binding of diverse chalcones with some preference for a slightly larger electron-rich group on the carbonyl side. We predict that further structure-activity relationship studies on chalcones with naphthalene or electron-rich groups near the carbonyl moiety will lead to the development of more potent PPARγ agonists.

Design, synthesis and identification of a new class of triarylmethyl amine compounds as inhibitors of apolipoprotein E production.

We have identified a new class of triarylmethyl amine compounds that can inhibit apolipoprotein E (apoE) production. ApoE is a cholesterol- and lipid-carrier protein implicated in aging, atherosclerosis, Alzheimer's Disease (AD), and other neurological and lipid-related disorders. Attenuation of apoE production is generally considered to be of therapeutic value. A majority of the apoE in the brain is produced by astrocytes. Here, we describe the design, synthesis, and biological screening of a small library of compounds that led to the identification of four triarylmethyl amines as potent inhibitors of apoE production in CCF-STTG1 astrocytoma cells.