Replication and fine mapping of asthma-associated loci in individuals of African ancestry

Asthma originates from genetic and environmental factors with about half the risk of disease attributable to heritable causes. Genome-wide association studies, mostly in populations of European ancestry, have identified numerous asthma-associated single nucleotide polymorphisms (SNPs). Studies in populations with diverse ancestries allow both for identification of robust associations that replicate across ethnic groups and for improved resolution of associated loci due to different patterns of linkage disequilibrium between ethnic groups. Here we report on an analysis of 745 African-American subjects with asthma and 3,238 African-American control subjects from the Candidate Gene Association Resource (CARe) Consortium, including analysis of SNPs imputed using 1,000 Genomes reference panels and adjustment for local ancestry. We show strong evidence that variation near RAD50/IL13, implicated in studies of European ancestry individuals, replicates in individuals largely of African ancestry. Fine mapping in African ancestry populations also refined the variants of interest for this association. We also provide strong or nominal evidence of replication at loci near ORMDL3/GSDMB, IL1RL1/IL18R1, and 10p14, all previously associated with asthma in European or Japanese populations, but not at the PYHIN1 locus previously reported in studies of African-American samples. These results improve the understanding of asthma genetics and further demonstrate the utility of genetic studies in populations other than those of largely European ancestry.     

The effect of repetitive transcranial magnetic stimulation on gamma oscillatory activity in schizophrenia

Background

Gamma (γ) oscillations (30–50 Hz) have been shown to be excessive in patients with schizophrenia (SCZ) during working memory (WM). WM is a cognitive process that involves the online maintenance and manipulation of information that is mediated largely by the dorsolateral prefrontal cortex (DLPFC). Repetitive transcranial magnetic stimulation (rTMS) represents a non-invasive method to stimulate the cortex that has been shown to enhance cognition and γ oscillatory activity during WM.

Methodology and Principal Findings

We examined the effect of 20 Hz rTMS over the DLPFC on γ oscillatory activity elicited during the N-back task in 24 patients with SCZ compared to 22 healthy subjects. Prior to rTMS, patients with SCZ elicited excessive γ oscillatory activity compared to healthy subjects across WM load. Active rTMS resulted in the reduction of frontal γ oscillatory activity in patients with SCZ, while potentiating activity in healthy subjects in the 3-back, the most difficult condition. Further, these effects on γ oscillatory activity were found to be specific to the frontal brain region and were absent in the parieto-occipital brain region.

Conclusions and Significance

We suggest that this opposing effect of rTMS on γ oscillatory activity in patients with SCZ versus healthy subjects may be related to homeostatic plasticity leading to differential effects of rTMS on γ oscillatory activity depending on baseline differences. These findings provide important insights into the neurophysiological mechanisms underlying WM deficits in SCZ and demonstrated that rTMS can modulate γ oscillatory activity that may be a possible avenue for cognitive potentiation in this disorder.     

The Distribution of Henipaviruses in Southeast Asia and Australasia: Is Wallace’s Line a Barrier to Nipah Virus?

Nipah virus (NiV) (Genus Henipavirus) is a recently emerged zoonotic virus that causes severe disease in humans and has been found in bats of the genus Pteropus. Whilst NiV has not been detected in Australia, evidence for NiV-infection has been found in pteropid bats in some of Australia’s closest neighbours. The aim of this study was to determine the occurrence of henipaviruses in fruit bat (Family Pteropodidae) populations to the north of Australia. In particular we tested the hypothesis that Nipah virus is restricted to west of Wallace’s Line. Fruit bats from Australia, Papua New Guinea, East Timor and Indonesia were tested for the presence of antibodies to Hendra virus (HeV) and Nipah virus, and tested for the presence of HeV, NiV or henipavirus RNA by PCR. Evidence was found for the presence of Nipah virus in both Pteropus vampyrus and Rousettus amplexicaudatus populations from East Timor. Serology and PCR also suggested the presence of a henipavirus that was neither HeV nor NiV in Pteropus alecto and Acerodon celebensis. The results demonstrate the presence of NiV in the fruit bat populations on the eastern side of Wallace’s Line and within 500 km of Australia. They indicate the presence of non-NiV, non-HeV henipaviruses in fruit bat populations of Sulawesi and Sumba and possibly in Papua New Guinea. It appears that NiV is present where P. vampyrus occurs, such as in the fruit bat populations of Timor, but where this bat species is absent other henipaviruses may be present, as on Sulawesi and Sumba. Evidence was obtained for the presence henipaviruses in the non-Pteropid species R. amplexicaudatus and in A. celebensis. The findings of this work fill some gaps in knowledge in geographical and species distribution of henipaviruses in Australasia which will contribute to planning of risk management and surveillance activities.     

Multipoint Binding of the SLP-76 SH2 Domain to ADAP Is Critical for Oligomerization of SLP-76 Signaling Complexes in Stimulated T Cells

The adapter molecules SLP-76 and LAT play central roles in T cell activation by recruiting enzymes and other adapters into multiprotein complexes that coordinate highly regulated signal transduction pathways. While many of the associated proteins have been characterized, less is known concerning the mechanisms of assembly for these dynamic and potentially heterogeneous signaling complexes. Following T cell receptor (TCR) stimulation, SLP-76 is found in structures called microclusters, which contain many signaling complexes. Previous studies showed that a mutation to the SLP-76 C-terminal SH2 domain nearly abolished SLP-76 microclusters, suggesting that the SH2 domain facilitates incorporation of signaling complexes into microclusters. S. C. Bunnell, A. L. Singer, D. I. Hong, B. H. Jacque, M. S. Jordan, M. C. Seminario, V. A. Barr, G. A. Koretzky, and L. E. Samelson, Mol. Cell. Biol., 26:7155–7166, 2006). Using biophysical methods, we demonstrate that the adapter, ADAP, contains three binding sites for SLP-76, and that multipoint binding to ADAP fragments oligomerizes the SLP-76 SH2 domain in vitro. These results were complemented with confocal imaging and functional studies of cells expressing ADAP with various mutations. Our results demonstrate that all three binding sites are critical for SLP-76 microcluster assembly, but any combination of two sites will partially induce microclusters. These data support a model whereby multipoint binding of SLP-76 to ADAP facilitates the assembly of SLP-76 microclusters. This model has implications for the regulation of SLP-76 and LAT microclusters and, as a result, T cell signaling.     

A Simple Method for Mass-Production of Liposomes,in Particular Large Liposomes,Suitable for Delivery of Free Amino Acids to Filter Feeding Zooplankton

In marine fish larviculture the live feed organisms are often enriched in order to enhance their nutritional value. One of the challenges is to enhance the phospholipids (PL) content, and another is to enhance the content of specific water soluble nutrients, like free amino acids (FAA). There are a few studies where this has been achieved by the use of liposomes. The aim of this study was to develop a simple method for mass-production of liposomes within a size range of 1–5 μm a size range suitable to feed live food organisms. Furthermore, the liposomes should have a high FAA concentration and be stable under conditions typical for short-time enrichment of live feed organisms. The method used in the present study is based on a combination of a reverse-phase evaporation method for preparing liposomes and re-hydration of freeze-dried, empty liposomes. The liposomal membrane was made of soy phosphatydilcholine and was loaded with a highly concentrated free amino acids solution. Most of the liposomes produced were 2–8 μm in diameter and the FAA encapsulation efficiency was 42.6%. Two experiments simulating 2 hr of live food enrichment were used to evaluate the liposomes. The results showed the liposome did not disintegrate or aggregate when suspended in seawater and that only 9% of the FAA content of the liposomes was lost after 2 hr suspension. The developed method was easy and reliable, producing tens of grams of liposomes per batch.     

Structure Sensitivity of Amino Proton Exchange in 2′ - and 5′ - Guanosine Monophosphate Dianions

Abstract

Proton NMR line broadening methods were used to determine the rates of amino proton exchange for disordered 2′ - and 5′ - GMP dianions in aqueous solutions containing tetramethylammonium (TMA⁺) cations. Replacing TMA⁺ with Na⁺ does not substantially alter the exchange rates, provided that H-bonded, Na⁺-directed tetramer structures are absent. Activation enthalpies (kcal/mol) and entropies (eu) for 2′ - GMP are: ΔH^# = 18.5 ± 1.3, ΔS^# = 9.6 ± 4.2 for theTMA⁺ salt atpH 8.10, and ΔH^# = 14.7 ± 2.6, ΔS^# = -3.7 ± 8.0 for the Na⁺ salt at pH 8.11. Extrapolated values of pseudo first-order rate constants at 25° Care in the range of k = 1–10 sec^?1. At suitable concentrations and temperatures, the Na⁺ salts of both 2′ - and 5′ - GMP formed stacked and unstacked tetramer units. Relative to the exchange kinetics observed for the disordered nucleotide, the exchange process in the tetramer units was catalyzed in half the amino protons and inhibited in the other half. The catalytic process (k < 10³ sec^?3) has been attributed to amino protons not involved in interbase H-bonding, where as the inhibited process (k > 10^?1 sec^?1) was assigned to those protons which do form such bonds. The structure-catalyzed process in both the stacked and unstacked tetramers was manifested by a loss of NMR amino proton intensity due to weighted time-averaging with the resonance for bulk water. A bridging water molecule between an amino proton and a phosphate on an adjacent nucleotide in the tetramer unit may provide a mechanistic pathway for the structure-catalyzed process.     

Neuraminidase-Inhibiting Antibody Is a Correlate of Cross-Protection against Lethal H5N1 Influenza Virus in Ferrets Immunized with Seasonal Influenza Vaccine

In preparing for the threat of a pandemic of avian H5N1 influenza virus, we need to consider the significant delay (4 to 6 months) necessary to produce a strain-matched vaccine. As some degree of cross-reactivity between seasonal influenza vaccines and H5N1 virus has been reported, this was further explored in the ferret model to determine the targets of protective immunity. Ferrets were vaccinated with two intramuscular inoculations of trivalent inactivated split influenza vaccine or subcomponent vaccines, with and without adjuvant, and later challenged with a lethal dose of A/Vietnam/1203/2004 (H5N1) influenza virus. We confirmed that vaccination with seasonal influenza vaccine afforded partial protection against lethal H5N1 challenge and showed that use of either AlPO₄ or Iscomatrix adjuvant with the vaccine resulted in complete protection against disease and death. The protection was due exclusively to the H1N1 vaccine component, and although the hemagglutinin contributed to protection, the dominant protective response was targeted toward the neuraminidase (NA) and correlated with sialic acid cleavage-inhibiting antibody titers. Purified heterologous NA formulated with Iscomatrix adjuvant was also protective. These results suggest that adjuvanted seasonal trivalent vaccine could be used as an interim measure to decrease morbidity and mortality from H5N1 prior to the availability of a specific vaccine. The data also highlight that an inducer of cross-protective immunity is the NA, a protein whose levels are not normally monitored in vaccines and whose capacity to induce immunity in recipients is not normally assessed.