Mouse HORMAD1 and HORMAD2, two conserved meiotic chromosomal proteins, are depleted from synapsed chromosome axes with the help of TRIP13 AAA-ATPase

Meiotic crossovers are produced when programmed double-strand breaks (DSBs) are repaired by recombination from homologous chromosomes (homologues). In a wide variety of organisms, meiotic HORMA-domain proteins are required to direct DSB repair towards homologues. This inter-homologue bias is required for efficient homology search, homologue alignment, and crossover formation. HORMA-domain proteins are also implicated in other processes related to crossover formation, including DSB formation, inhibition of promiscuous formation of the synaptonemal complex (SC), and the meiotic prophase checkpoint that monitors both DSB processing and SCs. We examined the behavior of two previously uncharacterized meiosis-specific mouse HORMA-domain proteins-HORMAD1 and HORMAD2-in wild-type mice and in mutants defective in DSB processing or SC formation. HORMADs are preferentially associated with unsynapsed chromosome axes throughout meiotic prophase. We observe a strong negative correlation between SC formation and presence of HORMADs on axes, and a positive correlation between the presumptive sites of high checkpoint-kinase ATR activity and hyper-accumulation of HORMADs on axes. HORMADs are not depleted from chromosomes in mutants that lack SCs. In contrast, DSB formation and DSB repair are not absolutely required for depletion of HORMADs from synapsed axes. A simple interpretation of these findings is that SC formation directly or indirectly promotes depletion of HORMADs from chromosome axes. We also find that TRIP13 protein is required for reciprocal distribution of HORMADs and the SYCP1/SC-component along chromosome axes. Similarities in mouse and budding yeast meiosis suggest that TRIP13/Pch2 proteins have a conserved role in establishing mutually exclusive HORMAD-rich and synapsed chromatin domains in both mouse and yeast. Taken together, our observations raise the possibility that involvement of meiotic HORMA-domain proteins in the regulation of homologue interactions is conserved in mammals

Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life

Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation mechanisms are considered as potential explanations for this phenomenon. Leaf tissue physical properties have been associated with subsequent discolouration and these may be influenced by variation in nutrient availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has also been associated with a reduction in subsequent discolouration, although excess irrigation has been linked to increased discolouration potentially through leaf physical properties. These environmental factors, including high temperature and UV light intensities, often have impacts on levels of phenolic compounds linking the environmental responses to the biochemistry of the PPO pathway. Breeding strategies targeting the PALand PPOpathway biochemistry and environmental response genes are discussed as a more cost-effective method of mitigating oxidative discolouration then either modified atmosphere packaging or post-harvest treatments, although current understanding of the biochemistry means that such programs are likely to be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future

Somatostatin receptors 2 and 5 are preferentially expressed in proliferating endothelium

Angiogenesis is characterised by activation, migration and proliferation of endothelial cells and is central to the pathology of cancer, cardiovascular disease and chronic inflammation. Somatostatin is an inhibitory polypeptide that acts through five receptors (sst 1, 2, 3, 4, 5). Sst has previously been reported in endothelium, but their role remains obscure. Here, we report the expression of sst in human umbilical vein endothelial cells (HUVECs) in vitro, during proliferation and quiescence. A protocol for culturing proliferating and quiescent HUVECs was established, and verified by analysing cell cycle distribution in propidium-iodide-stained samples using flow cytometry. Sst mRNA was then quantified in nine proliferating and quiescent HUVEC lines using quantitative reverse transcriptase–polymerase chain reaction. Sst 2 and 5 were preferentially expressed in proliferating HUVECs. All samples were negative for sst 4. Sst 1 and 3 expression and cell cycle progression were unrelated. Immunostaining for sst 2 and 5 showed positivity in proliferating but not quiescent cells, confirming sst 2 and 5 protein expression. Inhibition of proliferating cells with somatostatin analogues Octreotide and SOM230, which have sst 5 activity, was found (Octreotide 10−10–10−6 M: 48.5–70.2% inhibition; SOM230 10−9–10−6 M: 44.9–65.4% inhibition) in a dose-dependent manner, suggesting that sst 5 may have functional activity in proliferation. Dynamic changes in sst 2 and 5 expression during the cell cycle and the inhibition of proliferation with specific analogues suggest that these receptors may have a role in angiogenesis

miRNA-135a promotes breast cancer cell migration and invasion by targeting HOXA10

<p>Abstract</p> <p>Background</p> <p>miRNAs are a group of small RNA molecules regulating target genes by inducing mRNA degradation or translational repression. Aberrant expression of miRNAs correlates with various cancers. Although miR-135a has been implicated in several other cancers, its role in breast cancer is unknown. <it>HOXA10 </it>however, is associated with multiple cancer types and was recently shown to induce p53 expression in breast cancer cells and reduce their invasive ability. Because <it>HOXA10 </it>is a confirmed miR-135a target in more than one tissue, we examined miR-135a levels in relation to breast cancer phenotypes to determine if miR-135a plays role in this cancer type.</p> <p>Methods</p> <p>Expression levels of miR-135a in tissues and cells were determined by poly (A)-RT PCR. The effect of miR-135a on proliferation was evaluated by CCK8 assay, cell migration and invasion were evaluated by transwell migration and invasion assays, and target protein expression was determined by western blotting. GFP and luciferase reporter plasmids were constructed to confirm the action of miR-135a on downstream target genes including <it>HOXA10</it>. Results are reported as means ± S.D. and differences were tested for significance using 2-sided Student"s t-test.</p> <p>Results</p> <p>Here we report that miR-135a was highly expressed in metastatic breast tumors. We found that the expression of miR-135a was required for the migration and invasion of breast cancer cells, but not their proliferation. <it>HOXA10</it>, which encodes a transcription factor required for embryonic development and is a metastasis suppressor in breast cancer, was shown to be a direct target of miR-135a in breast cancer cells. Our analysis showed that miR-135a suppressed the expression of <it>HOXA10 </it>both at the mRNA and protein level, and its ability to promote cellular migration and invasion was partially reversed by overexpression of <it>HOXA10</it>.</p> <p>Conclusions</p> <p>In summary, our results indicate that miR-135a is an onco-miRNA that can promote breast cancer cell migration and invasion. <it>HOXA10 </it>is a target gene for miR-135a in breast cancer cells and overexpression of <it>HOXA10 </it>can partially reverse the miR-135a invasive phenotype.</p

MRSA prevalence in european healthcare settings: a review

<p>Abstract</p> <p>Background</p> <p>During the past two decades, methicillin-resistant <it>Staphylococcus aureus </it>(MRSA) has become increasingly common as a source of nosocomial infections. Most studies of MRSA surveillance were performed during outbreaks, so that results are not applicable to settings in which MRSA is endemic. This paper gives an overview of MRSA prevalence in hospitals and other healthcare institutions in non-outbreak situations in Western Europe.</p> <p>Methods</p> <p>A keyword search was conducted in the Medline database (2000 through June 2010). Titles and abstracts were screened to identify studies on MRSA prevalence in patients in non-outbreak situations in European healthcare facilities. Each study was assessed using seven quality criteria (outcome definition, time unit, target population, participants, observer bias, screening procedure, swabbing sites) and categorized as 'good', 'fair', or 'poor'.</p> <p>Results</p> <p>31 observational studies were included in the review. Four of the studies were of good quality. Surveillance screening of MRSA was performed in long-term care (11 studies) and acute care (20 studies). Prevalence rates varied over a wide range, from less than 1% to greater than 20%. Prevalence in the acute care and long-term care settings was comparable. The prevalence of MRSA was expressed in various ways - the percentage of MRSA among patients (range between 1% and 24%), the percentage of MRSA among <it>S. aureus </it>isolates (range between 5% and 54%), and as the prevalence density (range between 0.4 and 4 MRSA cases per 1,000 patient days). The screening policy differed with respect to time points (on admission or during hospital stay), selection criteria (all admissions or patients at high risk for MRSA) and anatomical sampling sites.</p> <p>Conclusions</p> <p>This review underlines the methodological differences between studies of MRSA surveillance. For comparisons between different healthcare settings, surveillance methods and outcome calculations should be standardized.</p

Pch2 Links Chromosome Axis Remodeling at Future Crossover Sites and Crossover Distribution during Yeast Meiosis

Segregation of homologous chromosomes during meiosis I depends on appropriately positioned crossovers/chiasmata. Crossover assurance ensures at least one crossover per homolog pair, while interference reduces double crossovers. Here, we have investigated the interplay between chromosome axis morphogenesis and non-random crossover placement. We demonstrate that chromosome axes are structurally modified at future crossover sites as indicated by correspondence between crossover designation marker Zip3 and domains enriched for axis ensemble Hop1/Red1. This association is first detected at the zygotene stage, persists until double Holliday junction resolution, and is controlled by the conserved AAA+ ATPase Pch2. Pch2 further mediates crossover interference, although it is dispensable for crossover formation at normal levels. Thus, interference appears to be superimposed on underlying mechanisms of crossover formation. When recombination-initiating DSBs are reduced, Pch2 is also required for viable spore formation, consistent with further functions in chiasma formation. pch2Δ mutant defects in crossover interference and spore viability at reduced DSB levels are oppositely modulated by temperature, suggesting contributions of two separable pathways to crossover control. Roles of Pch2 in controlling both chromosome axis morphogenesis and crossover placement suggest linkage between these processes. Pch2 is proposed to reorganize chromosome axes into a tiling array of long-range crossover control modules, resulting in chiasma formation at minimum levels and with maximum spacing

The endocrine tumor summit 2008: appraising therapeutic approaches for acromegaly and carcinoid syndrome

The Endocrine Tumor Summit convened in December 2008 to address 6 statements prepared by panel members that reflect important questions in the treatment of acromegaly and carcinoid syndrome. Data pertinent to each of the statements were identified through review of pertinent literature by one of the 9-member panel, enabling a critical evaluation of the statements and the evidence supporting or refuting them. Three statements addressed the validity of serum growth hormone (GH) and insulin-like growth factor-I (IGF-I) concentrations as indicators or predictors of disease in acromegaly. Statements regarding the effects of preoperative somatostatin analog use on pituitary surgical outcomes, their effects on hormone and symptom control in carcinoid syndrome, and the efficacy of extended dosing intervals were reviewed. Panel opinions, based on the level of available scientific evidence, were polled. Finally, their views were compared with those of surveyed community-based endocrinologists and neurosurgeons