Expectation mismatch: differences between self-generated and cue-induced expectations

Expectation of upcoming stimuli and tasks can lead to improved performance, if the anticipated situation occurs, while expectation mismatch can lead to less efficient processing. Researchers have used methodological approaches that rely on either self-generated expectations (predictions) or cue-induced expectations to investigate expectation mismatch effects. Differentiating these two types of expectations for different contents of expectation such as stimuli, responses, task sets and conflict level, we review evidence suggesting that self-generated expectations lead to larger facilitating effects and conflict effects on the behavioral and neural level - as compared to cue-based expectations. On a methodological level, we suggest that self-generated as compared to cue-induced expectations allow for a higher amount of experimental control in many experimental designs on expectation effects. On a theoretical level, we argue for qualitative differences in how cues vs. self-generated expectations influence performance. While self-generated expectations might generally involve representing the expected event in the focus of attention in working memory, cues might only lead to such representations under supportive circumstances (i.e., cue of high validity and attended).

Exposing the third chromosome of Burkholderia cepacia complex strains as a virulence plasmid

The Burkholderia cepacia complex (Bcc) consists of 17 closely related species of opportunistic bacterial pathogens, which are particularly problematic for cystic fibrosis patients and immunocompromised individuals. Bcc genomes consist of multiple replicons, and each strain sequenced to date has three chromosomes. In addition to genes thought to be essential for survival, each chromosome carries at least one rRNA operon. We isolated three mutants during a transposon mutagenesis screen that were non-pathogenic in a Caenorhabditis elegans infection model. It was demonstrated that these mutants had lost chromosome 3 (c3), and that the observed attenuation of virulence was a consequence of this. We constructed a c3 mini-replicon and used it to cure c3 from strains of several Bcc species by plasmid incompatibility, resulting in nine c3-null strains covering seven Bcc species. Phenotypic characterization of c3-null mutants revealed that they were attenuated in virulence in multiple infection hosts (rat, zebrafish, C. elegans, Galleria mellonella and Drosophila melanogaster), that they exhibited greatly diminished antifungal activity, and that c3 was required for d-xylose, fatty acid and pyrimidine utilization, as well as for exopolysaccharide production and proteolytic activity in some strains. In conclusion, we show that c3 is not an essential chromosomal element, rather a large plasmid that encodes virulence, secondary metabolism and other accessory functions in Bcc bacteria.

TET2 mutations and their clinical correlates in polycythemia vera, essential thrombocythemia and myelofibrosis

High-throughput DNA sequence analysis was used to screen for TET2 mutations in bone marrow-derived DNA from 239 patients with BCR-ABL-negative myeloproliferative neoplasms (MPNs). Thirty-two mutations (19 frameshift, 10 nonsense, 3 missense; mostly involving exons 4 and 12) were identified for an overall mutational frequency of approximately 13%. Specific diagnoses included polycythemia vera (PV; n=89), essential thrombocythemia (ET; n=57), primary myelofibrosis (PMF; n=60), post-PV MF (n=14), post-ET MF (n=7) and blast phase PV/ET/MF (n=12); the corresponding mutational frequencies were approximately 16, 5, 17, 14, 14 and 17% (P=0.50). Mutant TET2 was detected in approximately 17 and approximately 7% of JAK2V617F-positive and -negative cases, respectively (P=0.04). However, this apparent clustering of the two mutations was accounted for by an independent association between mutant TET2 and advanced age; mutational frequency was approximately 23% in patients > or =60 years old versus approximately 4% in younger patients (P<0.0001). The presence of mutant TET2 did not affect survival, leukemic transformation or thrombosis in either PV or PMF; a correlation with hemoglobin <10 g per 100 ml in PMF was noted (P=0.05). We conclude that TET2 mutations occur in both JAK2V617F-positive and -negative MPN, are more prevalent in older patients, display similar frequencies across MPN subcategories and disease stages, and hold limited prognostic relevance.

Increased KIT signalling with up-regulation of cyclin D correlates to accelerated proliferation and shorter disease-free survival in gastrointestinal stromal tumours (GISTs) with KIT exon 11 deletions

Gastrointestinal stromal tumours (GISTs) with deletions in KIT exon 11 are characterized by higher proliferation rates and shorter disease-free survival times, compared to GISTs with KIT exon 11 point mutations. Up-regulation of cyclin D is a crucial event for entry into the G1 phase of the cell cycle, and links mitogenic signalling to cell proliferation. Signalling from activated KIT to cyclin D is directed through the RAS/RAF/ERK, PI3K/AKT/mTOR/EIF4E, and JAK/STATs cascades. ERK and STATs initiate mRNA transcription of cyclin D, whereas EIF4E activation leads to increased translation efficiency and reduced degradation of cyclin D protein. The aim of the current study was to analyse the mRNA and protein expression as well as protein phosphorylation of central hubs of these signalling cascades in primary GISTs, to evaluate whether tumours with KIT exon 11 deletions and point mutations differently utilize these pathways. GISTs with KIT exon 11 deletions had significantly higher mitotic counts, higher proliferation rates, and shorter disease-free survival times. In line with this, they had significantly higher expression of cyclin D on the mRNA and protein level. Furthermore, there was a significantly higher amount of phosphorylated ERK1/2, and a higher protein amount of STAT3, mTOR, and EIF4E. PI3K and phosphorylated AKT were also up-regulated, but this was not significant. Ultimately, GISTs with KIT exon 11 deletions had significantly higher phosphorylation of the central negative cell-cycle regulator RB. Phosphorylation of RB is accomplished by activated cyclin D/CDK4/6 complex, and marks a central event in the release of the cell cycle. Altogether, these observations suggest increased KIT signalling with up-regulation of cyclin D as the basis for the unfavourable clinical course in GISTs with KIT exon 11 deletions.

Risk stratification for survival and leukemic transformation in essential thrombocythemia: a single institutional study of 605 patients

Unlike the case with thrombosis, prognostic models for survival and leukemic transformation (LT) in essential thrombocythemia (ET) are not available. Among 605 patients with ET seen at our institution and followed for a median of 84 months, 155 died and LT was documented in 20 patients (3.3%). In a multivariable analysis, hemoglobin level below normal (females<120 g/l; males<135 g/l) was identified as an independent risk factor for both inferior survival and LT. Additional risk factors for survival included age > or =60 years, leukocyte count> or =15 x 10(9)/l, smoking, diabetes mellitus and thrombosis. For LT, platelet count> or =1000 x 10(9)/l but not cytoreductive therapy was flagged as an additional independent risk factor. In fact, four of the 20 patients (20%) with LT were untreated previously. We used the above information to construct prognostic models that effectively discriminated among low-, intermediate- and high-risk groups with respective median survivals of 278, 200 and 111 months (P<0.0001), and LT rates of 0.4, 4.8 and 6.5% (P=0.0009) respectively. Presence of JAK2V617F did not impact either survival or LT and mutational frequency was similar among the different risk groups.

Variability of sperm specific histones in sea urchins

The variability of sperm histones was compared in two species of sea urchin. Whole sperm specific histones (SpH), were isolated from Tetrapygus niger (Arbacoida) and Parechinus angulosus (Echinoida). Individual histones were purified by chromatography on BioGel P-60 followed by reverse high pressure liquid chromatography (HPLC). The heterogeneity of each major histone type from T. niger was established from their HPLC elution patterns and further confirmed by electrophoresis in polyacrylamide gels containing 6 mM Triton X-100 combined with a transverse urea gradient (0--8 M). In T. niger, as well as in P. angulosus, a single form of SpH1 and SpH2A were found. In contrast, SpH2B was found to be heterogeneous, but represented by one major form in both species. The relatedness between both sets of histones was determined by establishing their immunological cross-reactivity. In this context, polyclonal antibodies elicited against T. niger sperm histones were assayed against individual histones from P. angulosus. From the results obtained, it emerged that histone SpH2A was the more closely related protein between these two species, followed by histone SpH1. In contrast, histone SpH2B was found to be only moderately related. These results confirm that SpH2A did not co-evolve with SpH2B, as was predicted for most species.

The identity of conformational states of reconstituted and native histone octamers

Histone octamers were reconstituted from the following preparations: (a) natural histone H3-H4 tetramer and histone H2A-H2B dimer, either selectively extracted from chromatin with solutions chloride or prepared by dissociation of the natural octamer; (b) acid-denatured core histones, either an unfractionated mixture or individually purified proteins. Complexes assembled from these histones elute from exclusion chromatography columns with octamer size as verified by cross-linking with dimethylsuberimidate. The reconstituted octamers all crystallize in the same form of helical tubes as the natural octamer.