Transferrin receptor 1 is a cellular receptor for New World haemorrhagic fever arenaviruses

At least five arenaviruses cause viral haemorrhagic fevers in humans. Lassa virus, an Old World arenavirus, uses the cellular receptor alpha-dystroglycan to infect cells. Machupo, Guanarito, Junin and Sabia viruses are New World haemorrhagic fever viruses that do not use alpha-dystroglycan. Here we show a specific, high-affinity association between transferrin receptor 1 (TfR1) and the entry glycoprotein (GP) of Machupo virus. Expression of human TfR1, but not human transferrin receptor 2, in hamster cell lines markedly enhanced the infection of viruses pseudotyped with the GP of Machupo, Guanarito and Junin viruses, but not with those of Lassa or lymphocytic choriomeningitis viruses. An anti-TfR1 antibody efficiently inhibited the replication of Machupo, Guanarito, Junin and Sabia viruses, but not that of Lassa virus. Iron depletion of culture medium enhanced, and iron supplementation decreased, the efficiency of infection by Junin and Machupo but not Lassa pseudoviruses. These data indicate that TfR1 is a cellular receptor for New World haemorrhagic fever arenaviruses.     

The crystal structure of the AgamOBP1•Icaridin complex reveals alternative binding modes and stereo-selective repellent recognition

Anopheles gambiae Odorant Binding Protein 1 in complex with the most widely used insect repellent DEET, was the first reported crystal structure of an olfactory macromolecule with a repellent, and paved the way for OBP1-structure-based approaches for discovery of new host-seeking disruptors. In this work, we performed STD-NMR experiments to directly monitor and verify the formation of a complex between AgamOBP1 and Icaridin, an efficient DEET alternative. Furthermore, Isothermal Titration Calorimetry experiments provided evidence for two Icaridin-binding sites with different affinities (Kd = 0.034 and 0.714 mM) and thermodynamic profiles of ligand binding. To elucidate the binding mode of Icaridin, the crystal structure of AgamOBP1?Icaridin complex was determined at 1.75 Å resolution. We found that Icaridin binds to the DEET-binding site in two distinct orientations and also to a novel binding site located at the C-terminal region. Importantly, only the most active 1R,2S-isomer of Icaridin’s equimolar diastereoisomeric mixture binds to the AgamOBP1 crystal, providing structural evidence for the possible contribution of OBP1 to the stereoselectivity of Icaridin perception in mosquitoes. Structural analysis revealed two ensembles of conformations differing mainly in spatial arrangement of their sec-butyl moieties. Moreover, structural comparison with DEET indicates a common recognition mechanism for these structurally related repellents. Ligand interactions with both sites and binding modes were further confirmed by 2D ¹H-¹⁵N HSQC NMR spectroscopy. The identification of a novel repellent-binding site in AgamOBP1 and the observed structural conservation and stereoselectivity of its DEET/Icaridin-binding sites open new perspectives for the OBP1-structure-based discovery of next-generation insect repellents.     

A genome-wide association study of metabolic traits in human urine

We present a genome-wide association study of metabolic traits in human urine, designed to investigate the detoxification capacity of the human body. Using NMR spectroscopy, we tested for associations between 59 metabolites in urine from 862 male participants in the population-based SHIP study. We replicated the results using 1,039 additional samples of the same study, including a 5-year follow-up, and 992 samples from the independent KORA study. We report five loci with joint P values of association from 3.2 × 10(-19) to 2.1 × 10(-182). Variants at three of these loci have previously been linked with important clinical outcomes: SLC7A9 is a risk locus for chronic kidney disease, NAT2 for coronary artery disease and genotype-dependent response to drug toxicity, and SLC6A20 for iminoglycinuria. Moreover, we identify rs37369 in AGXT2 as the genetic basis of hyper-β-aminoisobutyric aciduria.     

Lamellipodia mediate the heterogeneity of central olfactory ensheathing cell interactions

The growth and guidance of primary olfactory axons are partly attributed to the presence of olfactory ensheathing cells (OECs). However, little is understood about the differences between the subpopulations of OECs and what regulates their interactions. We used OEC-axon assays and determined that axons respond differently to peripheral and central OECs. We then further purified OECs from anatomically distinct regions of the olfactory bulb. Cell behaviour assays revealed that OECs from the olfactory bulb were a functionally heterogeneous population with distinct differences which is consistent with their proposed roles in vivo. We found that the heterogeneity was regulated by motile lamellipodial waves along the shaft of the OECs and that inhibition of lamellipodial wave activity via Mek1 abolished the ability of the cells to distinguish between each other. These results demonstrate that OECs from the olfactory bulb are a heterogeneous population that use lamellipodial waves to regulate cell–cell recognition.     

Mutations in the colony stimulating factor 1 receptor (CSF1R) gene cause hereditary diffuse leukoencephalopathy with spheroids

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an autosomal-dominant central nervous system white-matter disease with variable clinical presentations, including personality and behavioral changes, dementia, depression, parkinsonism, seizures and other phenotypes. We combined genome-wide linkage analysis with exome sequencing and identified 14 different mutations affecting the tyrosine kinase domain of the colony stimulating factor 1 receptor (encoded by CSF1R) in 14 families with HDLS. In one kindred, we confirmed the de novo occurrence of the mutation. Follow-up sequencing identified an additional CSF1R mutation in an individual diagnosed with corticobasal syndrome. In vitro, CSF-1 stimulation resulted in rapid autophosphorylation of selected tyrosine residues in the kinase domain of wild-type but not mutant CSF1R, suggesting that HDLS may result from partial loss of CSF1R function. As CSF1R is a crucial mediator of microglial proliferation and differentiation in the brain, our findings suggest an important role for microglial dysfunction in HDLS pathogenesis.     

<Emphasis Type="Italic">O</Emphasis>-Mannosylation and human disease

Glycosylation of proteins is arguably the most prevalent co- and post-translational modification. It is responsible for increased heterogeneity and functional diversity of proteins. Here we discuss the importance of one type of glycosylation, specifically O-mannosylation and its relationship to a number of human diseases. The most widely studied O-mannose modified protein is alpha-dystroglycan (α-DG). Recent studies have focused intensely on α-DG due to the severity of diseases associated with its improper glycosylation. O-mannosylation of α-DG is involved in cancer metastasis, arenavirus entry, and multiple forms of congenital muscular dystrophy [1, 2]. In this review, we discuss the structural and functional characteristics of O-mannose-initiated glycan structures on α-DG, enzymes involved in the O-mannosylation pathway, and the diseases that are a direct result of disruptions within this pathway.     

EYS, encoding an ortholog of Drosophila spacemaker, is mutated in autosomal recessive retinitis pigmentosa

Using a positional cloning approach supported by comparative genomics, we have identified a previously unreported gene, EYS, at the RP25 locus on chromosome 6q12 commonly mutated in autosomal recessive retinitis pigmentosa. Spanning over 2 Mb, this is the largest eye-specific gene identified so far. EYS is independently disrupted in four other mammalian lineages, including that of rodents, but is well conserved from Drosophila to man and is likely to have a role in the modeling of retinal architecture.     

Genome-wide in situ exon capture for selective resequencing

Increasingly powerful sequencing technologies are ushering in an era of personal genome sequences and raising the possibility of using such information to guide medical decisions. Genome resequencing also promises to accelerate the identification of disease-associated mutations. Roughly 98% of the human genome is composed of repeats and intergenic or non-protein-coding sequences. Thus, it is crucial to focus resequencing on high-value genomic regions. Protein-coding exons represent one such type of high-value target. We have developed a method of using flexible, high-density microarrays to capture any desired fraction of the human genome, in this case corresponding to more than 200,000 protein-coding exons. Depending on the precise protocol, up to 55-85% of the captured fragments are associated with targeted regions and up to 98% of intended exons can be recovered. This methodology provides an adaptable route toward rapid and efficient resequencing of any sizeable, non-repeat portion of the human genome.