Failure to confirm genetic association between schizophrenia and markers on chromosome 1q23.3 in the region of the gene encoding the regulator of G-protein signaling 4 protein (RGS4).

The chromosome 1q23.3 region, which includes the RGS4 gene has been implicated in genetic susceptibility to schizophrenia by two linkage studies with lod scores of 6.35 and 3.20 and with positive lod between 2.00 and 3.00 scores in several other studies. Reduced post mortem RGS4 gene expression in the brain of schizophrenics was reported as well as positive allelic association between markers at the RGS4 gene locus and schizophrenia. We have attempted to replicate the finding of allelic association with schizophrenia in a UK based sample of 450 subjects with schizophrenia and 450 supernormal controls. We genotyped the same SNP marker alleles investigated in the earlier studies and also a di-nucleotide (GT)14 repeat microsatellite marker, which was 7 kb distal to RGS4. In the new UK sample there was no evidence for allelic or haplotypic association between RGS4 markers and schizophrenia. This might reflect genetic heterogeneity between the population samples, genotyping or other methodological problems. The finding weakens the evidence that mutations or variation in the RGS4 gene have an effect on schizophrenia susceptibility.     

One pot multi‐component synthesis of functionalized spiropyridine and pyrido[2,3‐d]pyrimidine scaffolds and their potent in‐vitro anti‐inflammatory and anti‐oxidant investigations

A new series of functionalized fused pyridines 4(a–i) and fused pyrido[2,3‐d]pyrimidines 8(a–c) were designed and synthesized through a multi‐component reaction where in pyridine ring formation step plays a key role. All the newly formed compounds were well characterized by spectral techniques such as FTIR, ¹HNMR, ¹³CNMR, HRMS and XRD. The potential therapeutic activities such as anti‐inflammatory activity by protein denaturation and RBC membrane stabilization methods, and anti‐oxidant activity by DPPH scavenging method of the newly synthesized compounds were studied. Interestingly, in‐vitro testing of these compounds reveals that the compounds 4d , 4g , 4i , 8a and 8b showed comparable anti‐inflammatory activity with respect to the standard drug, diclofenac. Similarly, fused pyridine 4f showed excellent anti‐oxidant activity when compared with the standard, ascorbic acid.     

Interleukin-13 Receptor α1-Dependent Responses in the Intestine Are Critical to Parasite Clearance

Nematode infection upregulates interleukin-4 (IL-4) and IL-13 and induces STAT6-dependent changes in gut function that promote worm clearance. IL-4 and IL-13 activate the type 2 IL-4 receptor (IL-4R), which contains the IL-13Rα1 and IL-4Rα chains. We used mice deficient in IL-13Rα1 (IL-13Rα1^−/−) to examine the contribution of IL-13 acting at the type 2 IL-4R to immune and functional responses to primary (Hb1) and secondary (Hb2) infections with the gastrointestinal nematode parasite Heligmosomoides bakeri. There were differences between strains in the IL-4 and IL-13 expression responses to Hb1 but not Hb2 infection. Following Hb2 infection, deficient mice had impaired worm expulsion and higher worm fecundity despite normal production of Th2-derived cytokines. The upregulation of IL-25 and IL-13Rα2 in Hb1- and Hb2-infected wild-type (WT) mice was absent in IL-13Rα1^−/− mice. Goblet cell numbers and resistin-like molecule beta (RELM-β) expression were attenuated significantly in IL-13Rα1^−/− mice following Hb2 infections. IL-13Rα1 contributes to the development of alternatively activated macrophages, but the type 1 IL-4R is also important. Hb1 infection had no effects on smooth muscle function or epithelial permeability in either strain, while the enhanced mucosal permeability and changes in smooth muscle function and morphology observed in response to Hb2 infection in WT mice were absent in IL-13Rα1^−/− mice. Notably, the contribution of claudin-2, which has been linked to IL-13, does not mediate the increased mucosal permeability following Hb2 infection. These results show that activation of IL-13Rα1 is critical for key aspects of the immune and functional responses to Hb2 infection that facilitate expulsion.     

Plasticity of hydrogen bond networks regulates mechanochemistry of cell adhesion complexes

Mechanical forces acting on cell adhesion receptor proteins regulate a range of cellular functions by formation and rupture of noncovalent interactions with ligands. Typically, force decreases the lifetimes of intact complexes (“slip bonds”), making the discovery that these lifetimes can also be prolonged (“catch bonds”) a surprise. We created a microscopic analytic theory by incorporating the structures of selectin and integrin receptors into a conceptual framework based on the theory of stochastic equations, which quantitatively explains a wide range of experimental data (including catch bonds at low forces and slip bonds at high forces). Catch bonds arise due to force-induced remodeling of hydrogen bond networks, a finding that also accounts for unbinding in structurally unrelated integrin–fibronectin and actomyosin complexes. For the selectin family, remodeling of hydrogen bond networks drives an allosteric transition resulting in the formation of the maximum number of hydrogen bonds determined only by the structure of the receptor and independent of the ligand. A similar transition allows us to predict the increase in the number of hydrogen bonds in a particular allosteric state of α₅β₁ integrin–fibronectin complex, a conformation which is yet to be crystallized. We also make a testable prediction that a single point mutation (Tyr51Phe) in the ligand associated with selectin should dramatically alter the nature of the catch bond compared with the wild type. Our work suggests that nature uses a ductile network of hydrogen bonds to engineer function over a broad range of forces.Cells communicate with each other and their surroundings to maintain tissue architecture, allow cellular movement, transduce signals, and heal wounds (1). Important components in many of these processes are cell adhesion molecules—proteins on cell surfaces that recognize and bind to ligands on other cells or the extracellular matrix (1, 2). For example, adhesion of leukocytes to the endothelial cells of the blood vessel is a vital step in rolling and capturing of blood cells in wound healing, and is mediated by the selectin class of receptor proteins (3). The functional responses of cell adhesion molecules are often mechanically transduced by shear stresses and forces arising from focal adhesions to the cytoskeleton or simply the flow of blood in the vasculature. Under stress, molecules undergo conformational changes, triggering biophysical, biochemical, and gene regulatory responses that have been the subject of intense research (4, 5). Lifetimes of adhesion complexes are typically expected to decrease as forces increase (6). However, the response of certain complexes to mechanical force exhibits a surprisingly counterintuitive phenomenon. Lifetimes increase over a range of low force values, corresponding to catch-bond behavior (7). At high forces, the lifetimes revert to the conventional decreasing behavior, characteristic of a slip bond (6). In retrospect, the plausible existence of catch bonds was already evident in early experiments by Greig and Brooks, who discovered that agglutination of human red blood cells using the lectin Con A increased under shear (8). Although not interpreted in terms of catch bonds, their data showed lower rates of unbinding with increasing force on the complex. Given the importance of mechanotransduction in cellular adhesions, a quantitative and structural understanding of this surprising phenomenon is imperative.Direct evidence for catch bonds in a wide variety of cell adhesion complexes has come from flow and atomic force microscopy (AFM) experiments in the last decade (9–11), along with examples from other load-bearing cellular complexes like actomyosin bonds (12) and microtubule–kinetochore attachments (13). The catch-bond lifetime exhibits nonmonotonic biphasic behavior—increasing up to a certain critical force and decreasing at larger forces. The structural mechanisms leading to catch-bond behavior have largely been elusive, although experiments have provided key insights for selectins (14, 15) and integrins (16, 17). In these systems, the rupture rate of the ligand from the receptor depends on an angle between two domains in the receptor molecule (Fig. 1). Conformations with smaller angles detach more slowly than those with large angles. In the case of integrins, multiple conformations at varying angles have been crystallized (17), whereas for selectins, only two (Fig. 1) have been found so far in the crystal structures (14). In the absence of an external force, the molecule fluctuates between conformations corresponding to a variety of angles, including the larger angles from which the ligand can rapidly detach. With the application of force, the two domains increasingly align along the force direction, restricting the system to small angles and longer lifetimes, until large forces again reduce the barrier to rupture.Open in a separate windowFig. 1.Abstraction of the model based on structure. (A) Crystal structure of P-selectin (14) in the bent conformation [Protein Data Bank (PDB) ID code: 1G1Q]; (B) the extended conformation (PDB ID code: 1G1S). The lectin (gray–beige) and EGF (green) domains are labeled, along with two regions of the ligand binding interface (B₀ and B₁, purple). The ligand (an N-terminal fragment of the glycoprotein PSGL-1) is only cocrystallized in the extended state. (C and D) Schematic conformations of our model, corresponding to A and B. (E and F) Plots of the potential U(r, θ) at F = 0 pN and F = 50 pN, respectively, with k₀ = 80 k_BT/nm², k₁ = 20 k_BT/nm², r₀ = 1.0 nm, and b = 2 nm. The energy U(b, θ) at the transition state is highlighted in red.Previously, theories based on kinetic models with the assumption of a phenomenological Bell-like coupling of rates to force (18–21) have been used to explain catch-bond behavior. However, the parameters extracted from these kinetic models cannot be easily related to microscopic physical processes in specific catch-bond systems. More importantly, such models merely rationalize the experimental data, and do not have predictive power. The large scale of catch-bond lifetimes, ∼10−10⁴ ms, makes it impossible to directly observe unbinding in a realistic all-atom simulation, much less the macroscopic consequences of mutations.Here, we solve the difficulties alluded to above by creating a new theoretical approach. By building on the insights from the structures of cell adhesion complexes, we introduce a microscopic theoretical model that captures the essential physics of the angle-dependent detachment, and its implications for catch-bond behavior. Taking a cue from the crystal structures of selectin and integrin, we construct a coarse-grained energy function for receptor–ligand interactions. The model yields an analytic expression for the bond lifetime as a function of force, which gives excellent fits to a broad range of experimental data on a number of systems. The extracted parameters have clear structural interpretations, and their values provide predictions for energetic and structural features like strength of hydrogen bonding networks at the receptor–ligand interface. Where estimates of these properties can be directly obtained from crystal structures, our predictions are in remarkable agreement. The energy scales identified through the model are specific enough to allow predictions for structures not yet crystallized, and suggest mutation experiments that would modify catch-bond behavior in quantifiable ways. For the selectins, we predict how a specific mutation in the PSGL-1 ligand will alter its unbinding from P-selectin under force, and provide new interpretation of data from L-selectin mutants (20). Interestingly, the experimental fits suggest that both P- and L-selectin have a characteristic, ligand-independent energy scale, determined by the chemistry of their binding interfaces. For integrins, we predict the strength of extra interactions that should be observed in a crystal structure of the α₅β₁–fibronectin complex in an open state. The generality of the theory is further established by obtaining quantitative agreement for the catch-bond behavior in actomyosin complexes. Our theory provides, to our knowledge, the first structural link between the catch- to slip-bond transition in cell adhesion complexes, covering a broad range of forces and lifetimes.     

Failure to confirm allelic association between markers at the CAPON gene locus and schizophrenia in a British sample.

BACKGROUND: Linkage studies have confirmed that chromosome 1q23.3 is a susceptibility locus for schizophrenia. It was then claimed that markers at the carboxyl-terminal PDZ ligand of neuronal nitric oxide synthase (CAPON) gene showed allelic association with schizophrenia in Canadian families. A second Chinese study found a base pair polymorphism at the CAPON gene also associated with schizophrenia. METHODS: We attempted replication using eight markers from the Canadian study in a UK based sample of 450 cases and 450 supernormal controls. RESULTS: We found no evidence for allelic or haplotypic association with schizophrenia for any of the markers found to be associated in the Canadian sample. CONCLUSIONS: The negative results might reflect genetic heterogeneity between the Canadian, Chinese and UK samples or be due to methodological problems. The present finding weakens the evidence that mutations or variation in the CAPON gene are causing genetic susceptibility to schizophrenia in European populations.     

DISC1 association, heterogeneity and interplay in schizophrenia and bipolar disorder

Disrupted in schizophrenia 1 (DISC1) has been associated with risk of schizophrenia, schizoaffective disorder, bipolar disorder, major depression, autism and Asperger syndrome, but apart from in the original translocation family, true causal variants have yet to be confirmed. Here we report a harmonized association study for DISC1 in European cohorts of schizophrenia and bipolar disorder. We identify regions of significant association, demonstrate allele frequency heterogeneity and provide preliminary evidence for modifying interplay between variants. Whereas no associations survived permutation analysis in the combined data set, significant corrected associations were observed for bipolar disorder at rs1538979 in the Finnish cohorts (uncorrected P=0.00020; corrected P=0.016; odds ratio=2.73+/-95% confidence interval (CI) 1.42-5.27) and at rs821577 in the London cohort (uncorrected P=0.00070; corrected P=0.040; odds ratio=1.64+/-95% CI 1.23-2.19). The rs821577 single nucleotide polymorphism (SNP) showed evidence for increased risk within the combined European cohorts (odds ratio=1.27+/-95% CI 1.07-1.51), even though significant corrected association was not detected (uncorrected P=0.0058; corrected P=0.28). After conditioning the European data set on the two risk alleles, reanalysis revealed a third significant SNP association (uncorrected P=0.00050; corrected P=0.025). This SNP showed evidence for interplay, either increasing or decreasing risk, dependent upon the presence or absence of rs1538979 or rs821577. These findings provide further support for the role of DISC1 in psychiatric illness and demonstrate the presence of locus heterogeneity, with the effect that clinically relevant genetic variants may go undetected by standard analysis of combined cohorts.     

Dry amyloid fibril assembly in a yeast prion peptide is mediated by long-lived structures containing water wires

Amyloid-like fibrils from a number of small peptides that are unrelated by sequence adopt a cross-β-spine in which the two sheets fully interdigitate to create a dry interface. Formation of such a dry interface is usually associated with self-assembly of extended hydrophobic surfaces. Here we investigate how a dry interface is created in the process of protofilament formation in vastly different sequences using two amyloidogenic peptides, one a polar sequence from the N terminus of the yeast prion Sup35 and the other a predominantly hydrophobic sequence from the C terminus of Aβ-peptide. Using molecular dynamics simulations with three force fields we show that spontaneous formation of two ordered one-dimensional water wires in the pore between the two sheets of the Sup35 protofilaments results in long-lived structures, which are stabilized by a network of hydrogen bonds between the water molecules in the wires and the polar side chains in the β-sheet. Upon decreasing the stability of the metastable structures, water molecules are expelled resulting in a helically twisted protofilament in which side chains from a pair of β-strands in each sheet pack perfectly resulting in a dry interface. Although drying in hydrophobically dominated interfaces is abrupt, resembling a liquid to vapor transition, we find that discrete transitions between the liquid to one-dimensional ordered water in the nanopore enclosed by the two β-sheets to dry interface formation characterizes protofilament assembly in the yeast prions. Indeed, as the two sheets of the hydrophobic Aβ-sequence approach each other, fibril formation and expulsion of water molecules occur rapidly and nearly simultaneously.