Loss of imprinting of IGF2 and H19 in osteosarcoma is accompanied by reciprocal methylation changes of a CTCF-binding site

The adjacent insulin-like growth factor 2 (IGF2) and H19 genes are imprinted in most normal human tissues, but imprinting is often lost in tumors. The mechanisms involved in maintenance of imprinting (MOI) and loss of imprinting (LOI) are unresolved. We show here that osteosarcoma (OS) tumors with IGF2/H19 MOI exhibit allele-specific differential methylation of a CTCF-binding site upstream of H19. LOI of IGF2 or H19 in OS occurs in a mutually exclusive manner, and occurs with monoallelic expression of the other gene. Bisulfite sequencing reveals IGF2 LOI occurs with biallelic CpG methylation of the CTCF-binding site, while H19 LOI occurs with biallelic hypomethylation of this site. Our data demonstrate that IGF2 LOI and H19 LOI are accompanied by reciprocal methylation changes at a critical CTCF-binding site. We propose a model in which incomplete gain or loss of methylation at this CTCF-binding site during tumorigenesis explains the complex and often conflicting expression patterns of IGF2 and H19 in tumors.     

3'-Terminal RNA secondary structures are important for accumulation of tomato bushy stunt virus DI RNAs

The plus-strand RNA genome of tomato bushy stunt virus (TBSV) contains a 351-nucleotide (nt)-long 3'-untranslated region. We investigated the role of the 3'-proximal 130 nt of this sequence in viral RNA accumulation within the context of a TBSV defective interfering (DI) RNA. Sequence comparisons between different tombusviruses revealed that the 3' portion of the 130-nt sequence is highly conserved and deletion analysis confirmed that this segment is required for accumulation of DI RNAs in protoplasts. Computer-aided sequence analysis and in vitro solution structure probing indicated that the conserved sequence consists of three stem-loop (SL) structures (5'-SL3-SL2-SL1-3'). The existence of SLs 1 and 3 was also supported by comparative secondary structure analysis of sequenced tombusvirus genomes. Formation of the stem regions in all three SLs was found to be very important, and modification of the terminal loop sequences of SL1 and SL2, but not SL3, decreased DI RNA accumulation in vivo. For SL3, alterations to an internal loop resulted in significantly reduced DI RNA levels. Collectively, these data indicate that all three SLs are functionally relevant and contribute substantially to DI RNA accumulation. In addition, secondary structure analysis of other tombusvirus replicons and related virus genera revealed that a TBSV satellite RNA and members of the closely related genus Aureusvirus (family Tombusviridae) share fundamental elements of this general structural arrangement. Thus, this secondary structure model appears to extend beyond tombusvirus genomes. These conserved 3'-terminal RNA elements likely function in vivo by promoting and/or regulating minus-strand synthesis.     

Septins: a ring to part mother and daughter

The septins are well conserved GTPases found in animals and fungi. In yeast, they are required for the formation of 10-nm filaments, with which they co-localize at the bud neck. Therefore, septins have been proposed to be components of the neck filaments and to have polymerization properties. In support of this hypothesis, septin complexes purified from yeast and flies form filaments in vitro. However, recent studies have questioned the relevance of septin filament formation for septin function. Particularly, septin polymerization may not be required for their function in cytokinesis. New septin functions have also been recently uncovered: in budding yeast, the septin ring is required for the maintenance of cell polarity. It forms a cortical barrier that prevents lateral diffusion of membrane-associated proteins through the bud neck. Here, we review the most recent functional and biochemical data, to discuss whether there is a link between septin polymerization properties and septin function.     

Genetic Conservation of Hemagglutinin Gene of H9 Influenza Virus in Chicken Population in Mainland China

The hemagglutinin (HA) genes of 12 H9N2 influenza virus strains isolated from chickens in Mainland China during the period 1995–2002 were genetically analyzed. All the isolates possessed the same amino acid motif -R-S-S-R/G-L- at the cleavage site of HA. Except for the conserved amino acids, as is the case in the other avian influenza viruses, located in the receptor binding site, all of the 12 isolates possessed N at amino acid position 183; A, T, or V at position 190; K at position 137, whereas the representative strains of the other lineage (except Dk/HK/Y280/97-like lineage) virus of H9N2 viruses had H, E, and R at these positions respectively. These could be considered as the partial molecular markers of the H9 viruses isolated from chickens in Mainland China. Phylogenetic analyses showed HA genes of these isolates belonged to that of A/duck/Hong Kong/Y280/97-like virus lineage. No A/quail/Hong Kong/Gl/97-like virus was found in chicken, population since the outbreak of H9N2 influenza in Mainland China in 1992. The available evidence indicates that HA genes of H9 influenza virus circulating in Mainland China during the past years were well conserved.     

Comparison of disseminated and nondisseminated strains of Borrelia burgdorferi sensu stricto in mice naturally infected by tick bite

Clinical isolates of Borrelia burgdorferi sensu stricto have been categorized into disseminated and nondisseminated groups based on distinct ribosomal spacer restriction fragment length polymorphism genotypes (RSTs). In order to determine whether transmission by tick bite would alter the dissemination dynamics and disease produced by distinct genotypes, disseminated isolates (RST1), nondisseminated isolates (RST3), and a standard laboratory strain (B-31) were established in a murine cycle utilizing infections transmitted by ticks. B-31 spirochetes circulated in the blood of inbred C3H/HeJ mice longer than in the blood of outbred mice. The majority of C3H mice exposed to RST1-infected ticks contained cultivable spirochetes in their blood for up to 17 days; in contrast, mice exposed to RST3 isolates demonstrated a precipitous decline in infection after day 7 postexposure. A quantitative PCR (q-PCR) assay demonstrated that the densities of spirochetes in blood were similar for the RST1 and RST3 isolates, except during the 2nd week postexposure, when the RST1 isolates displayed a markedly higher density in blood. Spirochete load in the heart and bladder of infected mice was measured by q-PCR at 8 weeks postexposure; the numbers of spirochetes in these tissues were similar for mice infected with either disseminated or nondisseminated strains. Similarly, histopathology samples of heart, bladder, and joint tissue obtained at 8 weeks postexposure did not reveal greater pathology in mice infected with the disseminated isolates. We conclude that although the spirochetemia induced by tick-transmitted disseminated isolates was more intense and of longer duration than that induced by nondisseminated isolates, the resultant pathologies produced by these strains were ultimately similar.     

Targeting of the actin cytoskeleton during infection by Salmonella strains

Many bacterial pathogens produce virulence factors that alter the host cell cytoskeleton to promote infection. Salmonella strains target cellular actin in a carefully orchestrated series of interactions that promote bacterial uptake into host cells and the subsequent proliferation and intercellular spread of the organisms. The Salmonella Pathogenicity Island 1 (SPI1) locus encodes a type III protein secretion system (TTSS) that translocates effector proteins into epithelial cells to promote bacterial invasion through actin cytoskeletal rearrangements. SPI1 effectors interact directly with actin and also alter the cytoskeleton through activation of the regulatory proteins, Cdc42 and Rac, to produce membrane ruffles that engulf the bacteria. SPI1 also restores normal cellular actin dynamics through the action of another effector, SptP. A second TTSS, Salmonella Pathogenecity Island 2 (SPI2), translocates effectors that promote intracellular survival and growth, accompanied by focal actin polymerization around the Salmonella-containing vacuole (SCV). A number of Salmonella strains also carry the spv virulence locus, encoding an ADP-ribosyl transferase, the SpvB protein, which acts later during intracellular infection to depolymerize the actin cytoskeleton. SpvB produces a cytotoxic effect on infected host cells leading to apoptosis. The SpvB effect appears to promote intracellular infection and may facilitate cell-to-cell spread of the organism, thereby enhancing virulence.     

A new species of <Emphasis Type="Italic">Aplectana</Emphasis> (Nematoda,Cosmocercidae) in <Emphasis Type="Italic">Platymantis boulengeri</Emphasis> (Anura,Ceratobatrachidae) from Papua New Guinea

Aplectana krausi sp. nov. (Ascaridida, Cosmocercidae) from the intestines of Platymantis boulengeri (Anura, Ceratobatrachidae) is described and illustrated. Aplectana krausi represents the 42nd species assigned to the genus, the 4th species reported from the Australo-Papuan region. It is easily separated from the three species previously reported from the region by the distribution pattern of male caudal papillae: A. macintoshii and A. novaezelandiae have irregular patterns; A. zweifeli and A. krausi have defined patterns. Aplectana zweifeli has 8–10 precloacal, no adcloacal, and 9 postcloacal pairs of papillae, there is a single median papillae just anterior to the cloaca; A. krausi has 5 precloacal, 1 adcloacal, and 5 postcloacal pairs of papillae, a median papillae is absent.     

Association analysis of chromosome 1 migraine candidate genes

Background  

Migraine with aura (MA) is a subtype of typical migraine. Migraine with aura (MA) also encompasses a rare severe subtype Familial Hemiplegic Migraine (FHM) with several known genetic loci. The type 2 FHM (FHM-2) susceptibility locus maps to chromosome 1q23 and mutations in the ATP1A2 gene at this site have recently been implicated. We have previously provided evidence of linkage of typical migraine (predominantly MA) to microsatellite markers on chromosome 1, in the 1q31 and 1q23 regions. In this study, we have undertaken a large genomic investigation involving candidate genes that lie within the chromosome 1q23 and 1q31 regions using an association analysis approach.     

Investigation of Gamma-aminobutyric acid (GABA) A receptors genes and migraine susceptibility

Background  

Migraine is a neurological disorder characterized by recurrent attacks of severe headache, affecting around 12% of Caucasian populations. It is well known that migraine has a strong genetic component, although the number and type of genes involved is still unclear. Prior linkage studies have reported mapping of a migraine gene to chromosome Xq 24–28, a region containing a cluster of genes for GABA A receptors (GABRE, GABRA3, GABRQ), which are potential candidate genes for migraine. The GABA neurotransmitter has been implicated in migraine pathophysiology previously; however its exact role has not yet been established, although GABA receptors agonists have been the target of therapeutic developments. The aim of the present research is to investigate the role of the potential candidate genes reported on chromosome Xq 24–28 region in migraine susceptibility. In this study, we have focused on the subunit GABA A receptors type ε (GABRE) and type θ (GABRQ) genes and their involvement in migraine.