Characterization of mGluR5R,a novel,metabotropic glutamate receptor 5-related gene

We report here the isolation of a novel gene termed mGluR5R (mGluR5-related). The N-terminus of mGluR5R is highly similar to the extracellular domain of metabotropic glutamate receptor 5 (mGluR5) whereas the C-terminus bears similarity to the testis-specific gene, RNF18. mGluR5R is expressed in the human CNS in a coordinate fashion with mGluR5. Although the sequence suggests that mGluR5R may be a secreted glutamate binding protein, we found that when expressed in HEK293 cells it was membrane associated and not secreted. Furthermore, mGluR5R was incapable of binding the metabotropic glutamate receptor class I selective agonist, quisqualate. Although mGluR5R could not form disulfide-mediated covalent homodimers, it was able to form a homomeric complex, presumably through noncovalent interactions. mGluR5R also formed noncovalent heteromeric associations with an engineered construct of the extracellular domain of mGluR5 as well as with full-length mGluR5 and mGluR1alpha. The ability of mGluR5R to associate with mGluR1alpha and mGluR5 suggests that it may be a modulator of class I metabotropic glutamate receptor function.     

Iron-deficiency anaemia and delay in the diagnosis of colorectal cancer

Aims Iron‐deficiency anaemia (IDA) is a recognized complication of colorectal cancer (CRC) especially with right‐sided tumours, and failure to investigate the anaemia in older patients may lead to a delay in diagnosis. The aims of this study were to establish the proportion of patients with CRC shown to have an IDA for more than six months before diagnosis and to establish the proportion of patients with IDA who subsequently prove to have CRC. Methods All patients presenting with confirmed CRC in a health district (catchment population 280000) in the 4 years 1996–9 were identified from the pathology database after ethical approval. The criteria for IDA were haemoglobin (Hb) < 10.1 g/dl plus mean corpuscular volume < 78 fl and/or mean corpuscular Hb concentration < 32 g/dl. The haematology data‐base serving the same population was searched for evidence of: 1. IDA at diagnosis of CRC; 2. IDA more than 6 months and more than one year before the diagnosis of CRC; 3. The number of haematology referrals per annum in women over 55 and men over 50 years of age meeting the criteria for IDA. Results Of 440 patients with colorectal cancer, 166 (38%) had IDA at diagnosis and of the latter 54 (12%) were known to have IDA for more than six months before diagnosis and 26 (6%) had IDA more than one year before diagnosis. IDA was more common in right sided tumours (65%) than in those arising in the left side of the colon and rectum (26%). The annual incidence of IDA in the sampled population was 1366 in the stated age group. Conclusion The investigation of iron‐deficiency anaemia in older patients is important but in order to detect 26 patients with colorectal cancer a year earlier, the investigation of approximately 5000 patients would be required – a detection rate of less than 1%.     

Chromosome and gene copy number variation allow major structural change between species and strains of Leishmania

Leishmania parasites cause a spectrum of clinical pathology in humans ranging from disfiguring cutaneous lesions to fatal visceral leishmaniasis. We have generated a reference genome for Leishmania mexicana and refined the reference genomes for Leishmania major, Leishmania infantum, and Leishmania braziliensis. This has allowed the identification of a remarkably low number of genes or paralog groups (2, 14, 19, and 67, respectively) unique to one species. These were found to be conserved in additional isolates of the same species. We have predicted allelic variation and find that in these isolates, L. major and L. infantum have a surprisingly low number of predicted heterozygous SNPs compared with L. braziliensis and L. mexicana. We used short read coverage to infer ploidy and gene copy numbers, identifying large copy number variations between species, with 200 tandem gene arrays in L. major and 132 in L. mexicana. Chromosome copy number also varied significantly between species, with nine supernumerary chromosomes in L. infantum, four in L. mexicana, two in L. braziliensis, and one in L. major. A significant bias against gene arrays on supernumerary chromosomes was shown to exist, indicating that duplication events occur more frequently on disomic chromosomes. Taken together, our data demonstrate that there is little variation in unique gene content across Leishmania species, but large-scale genetic heterogeneity can result through gene amplification on disomic chromosomes and variation in chromosome number. Increased gene copy number due to chromosome amplification may contribute to alterations in gene expression in response to environmental conditions in the host, providing a genetic basis for disease tropism.     

Intranuclear Neuronal Inclusions in Huntington''s Disease and Dentatorubral and Pallidoluysian Atrophy: Correlation between the Density of Inclusions andIT15CAG Triplet Repeat Length

Huntington's disease (HD) is caused by CAG triplet repeat expansion inIT15which leads to polyglutamine stretches in the HD protein product, huntingtin. The pathological hallmark of HD is the degeneration of subsets of neurons, primarily those in the striatum and neocortex. Specific morphological markers of affected cells have not been identified in patients with HD, although a unique intranuclear inclusion was recently reported in neurons of transgenic animals expressing a construct encoding the N-terminal part (including the glutamine repeat) of huntingtin (Davieset al., 1997). In order to understand the importance of this finding, we sought for comparable nuclear abnormalities in autopsy material from patients with HD. In all 20 HD cases examined, anti-ubiquitin and N-terminal huntingtin antibodies identified intranuclear inclusions in neurons and the frequency of these lesions correlated with the length of the CAG repeat inIT15. In addition, examination of material from the related HD-like triplet repeat disorder, dentatorubral and pallidoluysian atrophy, also revealed intranuclear neuronal inclusions. These findings suggest that intranuclear inclusions containing protein aggregates may be a common feature of the pathogenesis of glutamine repeat neurodegenerative disorders.     

Organization of TNIK in dendritic spines

Tumor necrosis factor receptor‐associated factor 2 (TRAF2)‐ and noncatalytic region of tyrosine kinase (NCK)‐interacting kinase (TNIK) has been identified as an interactor in the psychiatric risk factor, Disrupted in Schizophrenia 1 (DISC1). As a step toward deciphering its function in the brain, we performed high‐resolution light and electron microscopic immunocytochemistry. We demonstrate here that TNIK is expressed in neurons throughout the adult mouse brain. In striatum and cerebral cortex, TNIK concentrates in dendritic spines, especially in the vicinity of the lateral edge of the synapse. Thus, TNIK is highly enriched at a microdomain critical for glutamatergic signaling. J. Comp. Neurol. 523:1913–1924, 2015 © 2015 Wiley Periodicals, Inc.     

Predicting Clostridium difficile Stool Cytotoxin Results in Hospitalized Patients with Diarrhea

OBJECTIVE: To validate a model for the prediction of Clostridium difficile cytotoxin assay results, and to identify a subgroup of patients with a very low likelihood of C. difficile-associated disease in whom the yield of routine cytotoxin testing is low. DESIGN: Prospective cohort study. Relevant clinical symptoms, signs, and antibiotic exposure were recorded before reporting of assay results. Each predictor was assigned a score based on regression coefficients, and patients were stratified according to their total score. SETTING: Two urban, tertiary care, university hospitals. PATIENTS: A total of 609 consecutive adult inpatients who received testing for C. difficile cytotoxin during a 3-month period in 1994. MEASUREMENTS AND MAIN RESULTS: The prevalence of positive cytotoxin assays was 8% in the validation set, compared with 14% in the derivation set. Defining patients without both prior antibiotic use and at least one symptom predictor (significant diarrhea or abdominal pain) as a low-risk subgroup, the misclassification rate was 2.8% (5/177) for assay results; of the five misclassified cases patients, only one was judged to have C. difficile-associated disease. Use of this rule to identify low-risk patients could have potentially averted 29% of all cytotoxin assays. CONCLUSIONS: Exposure to role models in a particular clinical field is strongly associated with medical students' choice of clinical field for residency training. Knowing which characteristics students look for in their role models should help identify the physicians who may be most influential in medical students' career choice.     

Avoiding collateral damage in the war on hypertension

• When performed by experienced clinicians, renal nerve denervation (RND) can be done with very low risk of complication and/or acute renal injury
• Renal function seems to remain unchanged in this small series over 3 years
• More studies are needed to establish the role of renal biomarkers in assessment of acute renal injury in this setting and larger series of RND in azotemic patients should be done before the procedure indications can be expanded

     

The Ubiquitin-Proteasome Reporter GFPu Does Not Accumulate in Neurons of the R6/2 Transgenic Mouse Model of Huntington's Disease

Impairment of the ubiquitin-proteasome system (UPS) has long been considered an attractive hypothesis to explain the selective dysfunction and death of neurons in polyglutamine disorders such as Huntington's disease (HD). The fact that inclusion bodies in HD mouse models and patient brains are rich in ubiquitin and proteasome components suggests that the UPS may be hindered directly or indirectly by inclusion bodies or their misfolded monomeric or oligomeric precursors. However, studies into UPS function in various polyglutamine disease models have yielded conflicting results, suggesting mutant polyglutamine tracts may exert different effects on the UPS depending on protein context, expression level, subcellular localisation and cell-type. To investigate UPS function in a well-characterised mouse model of HD, we have crossed R6/2 HD mice with transgenic UPS reporter mice expressing the GFPu construct. The GFPu construct comprises GFP fused to a constitutive degradation signal (CL-1) that promotes its rapid degradation under conditions of a healthy UPS. Using a combination of immunoblot analysis, fluorescence and immunofluorescence microscopy studies, we found that steady-state GFPu levels were not detectably different between R6/2 and non-R6/2 brain. We observed no correlation between inclusion body formation and GFPu accumulation, suggesting no direct relationship between protein aggregation and global UPS inhibition in R6/2 mice. These findings suggest that while certain branches of the UPS can be impaired by mutant polyglutamine proteins, such proteins do not necessarily cause total blockade of UPS-dependent degradation. It is therefore likely that the relationship between mutant polyglutamine proteins and the UPS is more complex than originally anticipated.