Zero area singularities in general relativity and inverse mean curvature flow

First we restate the definition of a Zero Area Singularity, recently introduced by H. Bray. We then consider several definitions of mass for these singularities. We use the Inverse Mean Curvature Flow to prove some new results about the mass of a singularity, the ADM mass of the manifold, and the capacity of the singularity.Comment: 13 page

Schizophrenia genomics: convergence on synaptic development, adult synaptic plasticity, or both?

Large-scale genomic studies of schizophrenia have identified hundreds of genetic loci conferring risk to the disorder. This progress offers an important route towards defining the biological basis of the condition and potentially developing new treatments. In this review, we discuss insights from recent genome-wide association study (GWAS), copy number variant (CNV) and exome sequencing analyses of schizophrenia, together with functional genomics data from the pre- and post-natal brain, in relation to synaptic development and function. These data provide strong support for the view that synaptic dysfunction within glutamatergic and GABAergic neurons of the cerebral cortex, hippocampus and other limbic structures is a central component of schizophrenia pathophysiology. Implicated genes and functional genomic data suggest that disturbances in synaptic connectivity associated with susceptibility to schizophrenia begin in utero but continue throughout development, with some alleles conferring risk to the disorder through direct effects on synaptic function in adulthood. This model implies that novel interventions for schizophrenia could include broad preventative approaches aimed at enhancing synaptic health during development as well as more targeted treatments aimed at correcting synaptic function in affected adults

Enhancer Priming Enables Fast and Sustained Transcriptional Responses to Notch Signaling.

Information from developmental signaling pathways must be accurately decoded to generate transcriptional outcomes. In the case of Notch, the intracellular domain (NICD) transduces the signal directly to the nucleus. How enhancers decipher NICD in the real time of developmental decisions is not known. Using the MS2-MCP system to visualize nascent transcripts in single cells in Drosophila embryos, we reveal how two target enhancers read Notch activity to produce synchronized and sustained profiles of transcription. By manipulating the levels of NICD and altering specific motifs within the enhancers, we uncover two key principles. First, increased NICD levels alter transcription by increasing duration rather than frequency of transcriptional bursts. Second, priming of enhancers by tissue-specific transcription factors is required for NICD to confer synchronized and sustained activity; in their absence, transcription is stochastic and bursty. The dynamic response of an individual enhancer to NICD thus differs depending on the cellular context.Wellcome Trus

Pain in malignant pleural mesothelioma: a prospective characterisation study.

INTRODUCTION: Malignant pleural mesothelioma (MPM) is associated with severe pain. The underlying neurobiology of this is complex. The primary aim of this study was to characterize pain in MPM. METHODS: This study was undertaken as part of a trial examining radiotherapy for the treatment of pain in MPM (ISRCTN 10644347). Patients had MPM with associated pain for which radiotherapy was planned and a worst pain score ≥ 4/10. The following assessments were undertaken: clinical neuropathic pain assessment, Brief Pain Inventory (BPI), Leeds Assessment of Neuropathic Symptoms and Signs (LANSS), Short form of the McGill Pain Questionnaire (SF-MPQ), and Quantitative Sensory Testing (QST). The relationship of these characteristics and response to radiotherapy was assessed. Unless stated, medians and interquartile range (IQR) are used. RESULTS: Thirty-seven patients were recruited. Average pain and worst pain was 4 (4-6) and 8 (6-8), respectively. Higher average pain and higher worst pain scores were associated with higher interference scores on the BPI, P < 0.001 and P < 0.0005. Twenty patients (54%) had a clinical diagnosis of neuropathic pain, and of these, only six patients (40%) screened positively for neuropathic pain using the LANSS. Patients with a high LANSS also had higher BPI and SF-MPQs. The presence of neuropathic pain (clinically or by LANSS) did not predict response to radiotherapy, P < 0.05. The SF-MPQ scores were higher in those with abnormal cool sensation on QST (P = 0.016). CONCLUSION: Pain in mesothelioma varies among patients and may have neuropathic components. An adequate pain assessment is necessary to guide the clinician in the appropriate choice of analgesics

Methylomic trajectories across human fetal brain development

Open access articleEpigenetic processes play a key role in orchestrating transcriptional regulation during development. The importance of DNA methylation in fetal brain development is highlighted by the dynamic expression of de novo DNA methyltransferases during the perinatal period and neurodevelopmental deficits associated with mutations in the methyl-CpG binding protein 2 (MECP2) gene. However, our knowledge about the temporal changes to the epigenome during fetal brain development has, to date, been limited. We quantified genome-wide patterns of DNA methylation at ∼ 400,000 sites in 179 human fetal brain samples (100 male, 79 female) spanning 23 to 184 d post-conception. We identified highly significant changes in DNA methylation across fetal brain development at >7% of sites, with an enrichment of loci becoming hypomethylated with fetal age. Sites associated with developmental changes in DNA methylation during fetal brain development were significantly underrepresented in promoter regulatory regions but significantly overrepresented in regions flanking CpG islands (shores and shelves) and gene bodies. Highly significant differences in DNA methylation were observed between males and females at a number of autosomal sites, with a small number of regions showing sex-specific DNA methylation trajectories across brain development. Weighted gene comethylation network analysis (WGCNA) revealed discrete modules of comethylated loci associated with fetal age that are significantly enriched for genes involved in neurodevelopmental processes. This is, to our knowledge, the most extensive study of DNA methylation across human fetal brain development to date, confirming the prenatal period as a time of considerable epigenomic plasticity.MRCUniversity of Exeter Medical SchoolWellcome Trus

Transcriptional changes following cellular knockdown of the schizophrenia risk gene SETD1A are enriched for common variant association with the disorder

Loss of function mutations in SETD1A are the first experiment-wide significant findings to emerge from exome sequencing studies of schizophrenia. Although SETD1A is known to encode a histone methyltransferase, the consequences of reduced SETD1A activity on gene expression in neural cells have, to date, been unknown. To explore transcriptional changes through which genetic perturbation of SETD1A could confer risk for schizophrenia, we have performed genome-wide gene expression profiling of a commonly used human neuroblastoma cell line in which SETD1A expression has been experimentally reduced using RNA interference (RNAi). We identified 1,031 gene expression changes that were significant in two separate RNAi conditions compared with control, including effects on genes of known neurodevelopmental importance such as DCX and DLX5. Genes that were differentially expressed following SETD1A knockdown were enriched for annotation to metabolic pathways, peptidase regulator activity and integrin-mediated regulation of cell adhesion. Moreover, differentially expressed genes were enriched for common variant association with schizophrenia, suggesting a degree of molecular convergence between this rare schizophrenia risk factor and susceptibility variants for the disorder operating more generally

Structure of the hexameric HerA ATPase reveals a mechanism of translocation-coupled DNA-end processing in archaea.

The HerA ATPase cooperates with the NurA nuclease and the Mre11-Rad50 complex for the repair of double-strand DNA breaks in thermophilic archaea. Here we extend our structural knowledge of this minimal end-resection apparatus by presenting the first crystal structure of hexameric HerA. The full-length structure visualizes at atomic resolution the N-terminal HerA-ATP synthase domain and a conserved C-terminal extension, which acts as a physical brace between adjacent protomers. The brace also interacts in trans with nucleotide-binding residues of the neighbouring subunit. Our observations support a model in which the coaxial interaction of the HerA ring with the toroidal NurA dimer generates a continuous channel traversing the complex. HerA-driven translocation would propel the DNA towards the narrow annulus of NurA, leading to duplex melting and nucleolytic digestion. This system differs substantially from the bacterial end-resection paradigms. Our findings suggest a novel mode of DNA-end processing by this integrated archaeal helicase-nuclease machine.The SAXS data collection was supported by funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under BioStruct-X (grant agreement N°283570). Research in the N.P.R. laboratory is funded by the Medical Research Council [Career Development Award G0701443]. Research in the L.P. laboratory is funded by a Wellcome Trust Senior Fellowship Award in Basic Biomedical Sciences [grant number 08279/Z/07/Z]. Work in the L.P. and N.P.R. laboratories is also supported by an Isaac Newton Trust Research Grant, and S.M.B. is supported by a BBSRC Doctoral Training Grant.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/ncomms650

Stochastic Choice of Allelic Expression in Human Neural Stem Cells

Abstract Monoallelic gene expression, such as genomic imprinting, is well described. Less well-characterized are genes undergoing stochastic monoallelic expression (MA), where specific clones of cells express just one allele at a given locus. We performed genome-wide allelic expression assessment of human clonal neural stem cells derived from cerebral cortex, striatum, and spinal cord, each with differing genotypes. We assayed three separate clonal lines from each donor, distinguishing stochastic MA from genotypic effects. Roughly 2% of genes showed evidence for autosomal MA, and in about half of these, allelic expression was stochastic between different clones. Many of these loci were known neurodevelopmental genes, such as OTX2 and OLIG2. Monoallelic genes also showed increased levels of DNA methylation compared to hypomethylated biallelic loci. Identified monoallelic gene loci showed altered chromatin signatures in fetal brain, suggesting an in vivo correlate of this phenomenon. We conclude that stochastic allelic expression is prevalent in neural stem cells, providing clonal diversity to developing tissues such as the human brain.</jats:p

Techniques for RNA extraction from cells cultured in starPEG-heparin hydrogels

Three-dimensional (3D) cell culture models that provide a biologically relevant microenvironment are imperative to investigate cell–cell and cell–matrix interactions in vitro. Semi-synthetic star-shaped poly(ethylene glycol) (starPEG)–heparin hydrogels are widely used for 3D cell culture due to their highly tuneable biochemical and biomechanical properties. Changes in gene expression levels are commonly used as a measure of cellular responses. However, the isolation of high-quality RNA presents a challenge as contamination of the RNA with hydrogel residue, such as polymer or glycosaminoglycan fragments, can impact template quality and quantity, limiting effective gene expression analyses. Here, we compare two protocols for the extraction of high-quality RNA from starPEG–heparin hydrogels and assess three subsequent purification techniques. Removal of hydrogel residue by centrifugation was found to be essential for obtaining high-quality RNA in both isolation methods. However, purification of the RNA did not result in further improvements in RNA quality. Furthermore, we show the suitability of the extracted RNA for cDNA synthesis of three endogenous control genes confirmed via quantitative polymerase chain reaction (qPCR). The methods and techniques shown can be tailored for other hydrogel models based on natural or semi-synthetic materials to provide robust templates for all gene expression analyses