Cyclic di-GMP signalling in the virulence and environmental adaptation of Xanthomonas campestris

Cyclic di-GMP is a second messenger with a role in regulation of a range of cellular functions in diverse bacteria including the virulence of pathogens. Cellular levels of cyclic di-GMP are controlled through synthesis, catalysed by the GGDEF protein domain, and degradation by EAL or HD-GYP domains. Here we report a comprehensive study of cyclic di-GMP signalling in bacterial disease in which we examine the contribution of all proteins with GGDEF, EAL or HD-GYP domains to virulence and virulence factor production in the phytopathogen Xanthomonas campestris pathovar campestris (Xcc). Genes with significant roles in virulence to plants included those encoding proteins whose probable function is in cyclic-di-GMP synthesis as well as others (including the HD-GYP domain regulator RpfG) implicated in cyclic di-GMP degradation. Furthermore, RpfG controlled expression of a subset of these genes. A partially overlapping set of elements controlled the production of virulence factors in vitro. Other GGDEF-EAL domain proteins had no effect on virulence factor synthesis but did influence motility. These findings indicate the existence of a regulatory network that may allow Xcc to integrate information from diverse environmental inputs to modulate virulence factor synthesis as well as of cyclic di-GMP signalling systems dedicated to other specific tasks.     

Seroprevalence of parvovirus B19 IgG in children affected by juvenile idiopathic arthritis

Parvovirus (PV) B19 is the causative agent of the childhood disease erythema infectiosum. An association of PV B19 with chronic arthropathies, sometimes resembling rheumatoid arthritis or juvenile idiopathic arthritis (JIA), has repeatedly been described. Other studies, however, have failed to identify any such relationship. In order to study further whether there is a link between PV B19 and JIA, we determined the prevalence of PV B19 specific IgG antibodies in serum samples from children with rheumatoid diseases and compared it with the prevalence in unaffected children We reasoned that if there is an association between PV B19 and JIA, then the prevalence of PV B19 IgG in the children with JIA should be higher than in the control group. PV B19 IgG status was tested in 406 children with JIA and related diseases, and in 146 children constituting a control group. The percentage of PV B19 IgG positive children was not significantly elevated in the disease subgroups compared with age-matched control groups. In conclusion, our findings do not support the hypothesis that human parvovirus B19 is involved in the pathogenesis of JIA.     

Mating system in a small pelagic spawner: field case study of the mandarinfish,Synchiropus splendidus

Environmental Biology of Fishes - Mating systems in fishes are extremely diverse, ranging from monogamy to multiple polygamous forms, some of which include alternative male mating tactics within...     

microRNA‐379 couples glucocorticoid hormones to dysfunctional lipid homeostasis

In mammals, glucocorticoids (GCs) and their intracellular receptor, the glucocorticoid receptor (GR), represent critical checkpoints in the endocrine control of energy homeostasis. Indeed, aberrant GC action is linked to severe metabolic stress conditions as seen in Cushing's syndrome, GC therapy and certain components of the Metabolic Syndrome, including obesity and insulin resistance. Here, we identify the hepatic induction of the mammalian conserved microRNA (miR)‐379/410 genomic cluster as a key component of GC/GR‐driven metabolic dysfunction. Particularly, miR‐379 was up‐regulated in mouse models of hyperglucocorticoidemia and obesity as well as human liver in a GC/GR‐dependent manner. Hepatocyte‐specific silencing of miR‐379 substantially reduced circulating very‐low‐density lipoprotein (VLDL)‐associated triglyceride (TG) levels in healthy mice and normalized aberrant lipid profiles in metabolically challenged animals, mediated through miR‐379 effects on key receptors in hepatic TG re‐uptake. As hepatic miR‐379 levels were also correlated with GC and TG levels in human obese patients, the identification of a GC/GR‐controlled miRNA cluster not only defines a novel layer of hormone‐dependent metabolic control but also paves the way to alternative miRNA‐based therapeutic approaches in metabolic dysfunction.     

Changes in Neuronal Dopamine Homeostasis following 1-Methyl-4-phenylpyridinium (MPP+) Exposure

1-Methyl-4-phenylpyridinium (MPP⁺), the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, selectively kills dopaminergic neurons in vivo and in vitro via a variety of toxic mechanisms, including mitochondrial dysfunction, generation of peroxynitrite, induction of apoptosis, and oxidative stress due to disruption of vesicular dopamine (DA) storage. To investigate the effects of acute MPP⁺ exposure on neuronal DA homeostasis, we measured stimulation-dependent DA release and non-exocytotic DA efflux from mouse striatal slices and extracellular, intracellular, and cytosolic DA (DA_cyt) levels in cultured mouse ventral midbrain neurons. In acute striatal slices, MPP⁺ exposure gradually decreased stimulation-dependent DA release, followed by massive DA efflux that was dependent on MPP⁺ concentration, temperature, and DA uptake transporter activity. Similarly, in mouse midbrain neuronal cultures, MPP⁺ depleted vesicular DA storage accompanied by an elevation of cytosolic and extracellular DA levels. In neuronal cell bodies, increased DA_cyt was not due to transmitter leakage from synaptic vesicles but rather to competitive MPP⁺-dependent inhibition of monoamine oxidase activity. Accordingly, monoamine oxidase blockers pargyline and l-deprenyl had no effect on DA_cyt levels in MPP⁺-treated cells and produced only a moderate effect on the survival of dopaminergic neurons treated with the toxin. In contrast, depletion of intracellular DA by blocking neurotransmitter synthesis resulted in ∼30% reduction of MPP⁺-mediated toxicity, whereas overexpression of VMAT2 completely rescued dopaminergic neurons. These results demonstrate the utility of comprehensive analysis of DA metabolism using various electrochemical methods and reveal the complexity of the effects of MPP⁺ on neuronal DA homeostasis and neurotoxicity.     

The Recruitment of AMP-activated Protein Kinase to Glycogen Is Regulated by Autophosphorylation

The mammalian AMP-activated protein kinase (AMPK) is an obligatory αβγ heterotrimeric complex carrying a carbohydrate-binding module (CBM) in the β-subunit (AMPKβ) capable of attaching AMPK to glycogen. Nonetheless, AMPK localizes at many different cellular compartments, implying the existence of mechanisms that prevent AMPK from glycogen binding. Cell-free carbohydrate binding assays revealed that AMPK autophosphorylation abolished its carbohydrate-binding capacity. X-ray structural data of the CBM displays the central positioning of threonine 148 within the binding pocket. Substitution of Thr-148 for a phospho-mimicking aspartate (T148D) prevents AMPK from binding to carbohydrate. Overexpression of isolated CBM or β1-containing AMPK in cellular models revealed that wild type (WT) localizes to glycogen particles, whereas T148D shows a diffuse pattern. Pharmacological AMPK activation and glycogen degradation by glucose deprivation but not forskolin enhanced cellular Thr-148 phosphorylation. Cellular glycogen content was higher if pharmacological AMPK activation was combined with overexpression of T148D mutant relative to WT AMPK. In summary, these data show that glycogen-binding capacity of AMPKβ is regulated by Thr-148 autophosphorylation with likely implications in the regulation of glycogen turnover. The findings further raise the possibility of regulated carbohydrate-binding function in a wider variety of CBM-containing proteins.     

Evolution of Influenza B Virus in Kuala Lumpur,Malaysia, between 1995 and 2008

Influenza B virus causes significant disease but remains understudied in tropical regions. We sequenced 72 influenza B viruses collected in Kuala Lumpur, Malaysia, from 1995 to 2008. The predominant circulating lineage (Victoria or Yamagata) changed every 1 to 3 years, and these shifts were associated with increased incidence of influenza B. We also found poor lineage matches with recommended influenza virus vaccine strains. While most influenza B virus lineages in Malaysia were short-lived, one circulated for 3 to 4 years.     

Impact of QTL properties on the accuracy of multi-breed genomic prediction

Background

Although simulation studies show that combining multiple breeds in one reference population increases accuracy of genomic prediction, this is not always confirmed in empirical studies. This discrepancy might be due to the assumptions on quantitative trait loci (QTL) properties applied in simulation studies, including number of QTL, spectrum of QTL allele frequencies across breeds, and distribution of allele substitution effects. We investigated the effects of QTL properties and of including a random across- and within-breed animal effect in a genomic best linear unbiased prediction (GBLUP) model on accuracy of multi-breed genomic prediction using genotypes of Holstein-Friesian and Jersey cows.

Methods

Genotypes of three classes of variants obtained from whole-genome sequence data, with moderately low, very low or extremely low average minor allele frequencies (MAF), were imputed in 3000 Holstein-Friesian and 3000 Jersey cows that had real high-density genotypes. Phenotypes of traits controlled by QTL with different properties were simulated by sampling 100 or 1000 QTL from one class of variants and their allele substitution effects either randomly from a gamma distribution, or computed such that each QTL explained the same variance, i.e. rare alleles had a large effect. Genomic breeding values for 1000 selection candidates per breed were estimated using GBLUP modelsincluding a random across- and a within-breed animal effect.

Results

For all three classes of QTL allele frequency spectra, accuracies of genomic prediction were not affected by the addition of 2000 individuals of the other breed to a reference population of the same breed as the selection candidates. Accuracies of both single- and multi-breed genomic prediction decreased as MAF of QTL decreased, especially when rare alleles had a large effect. Accuracies of genomic prediction were similar for the models with and without a random within-breed animal effect, probably because of insufficient power to separate across- and within-breed animal effects.

Conclusions

Accuracy of both single- and multi-breed genomic prediction depends on the properties of the QTL that underlie the trait. As QTL MAF decreased, accuracy decreased, especially when rare alleles had a large effect. This demonstrates that QTL properties are key parameters that determine the accuracy of genomic prediction.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-015-0124-6) contains supplementary material, which is available to authorized users.