Lymphomatous infilration of the peripheral nervous system in enteropathy-associated T-cell lymphoma

The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.Yoon-Sim Yap, Adrian Cummins, Peter Blumbergs, Jennifer Hardingham, Sunil Dabadghao and John Norma

Functional assessment of the NMDA receptor variant GluN2A (R586K)

Background: The N-methyl-D-aspartate receptor (NMDAR) is an ionotropic glutamate receptor that has important roles in synaptogenesis, synaptic transmission, and synaptic plasticity. Recently, a large number of rare genetic variants have been found in NMDAR subunits in people with neurodevelopmental disorders, and also in healthy individuals. One such is the GluN2AR586K variant (GRIN2AG1757A), found in a person with intellectual disability. Identifying the functional consequences, if any, of such variants allows their potential contribution to pathogenesis to be assessed. Here, we assessed the effect of the GluN2AR586K variant on NMDAR pore properties. Methods: We expressed recombinant NMDARs with and without the GluN2AR586K variant in Xenopus laevis oocytes and in primary cultured mouse neurons, and made electrophysiological recordings assessing Mg2+ block, single-channel conductance, mean open time and current density. Results: The GluN2AR586K variant was not found to influence any of the properties assessed. Conclusions: Our findings suggest it is unlikely that the GluN2AR586K variant contributes to the pathogenesis of neurodevelopmental disorder

Receptor protein tyrosine kinase EphB4 is up-regulated in colon cancer

BACKGROUND: We have used commercially available cDNA arrays to identify EphB4 as a gene that is up-regulated in colon cancer tissue when compared with matched normal tissue from the same patient. RESULTS: Quantitative RT-PCR analysis of the expression of the EphB4 gene has shown that its expression is increased in 82% of tumour samples when compared with the matched normal tissue from the same patient. Using immunohistochemistry and Western analysis techniques with an EphB4-specific antibody, we also show that this receptor is expressed in the epithelial cells of the tumour tissue and either not at all, or in only low levels, in the normal tissue. CONCLUSION: The results presented here supports the emerging idea that Eph receptors play a role in tumour formation and suggests that further elucidation of this signalling pathway may identify useful targets for cancer treatment therapies

Extracellular Calcium Regulates Postsynaptic Efficacy through Group 1 Metabotropic Glutamate Receptors

Bursts of synaptic transmission are known to induce transient depletion of Ca2+ within the synaptic cleft. Although Ca2+ depletion has been shown to lower presynaptic release probability, effects on the postsynaptic cell have not been reported. In this study, we show that physiologically relevant reductions in extracellular Ca2+ lead to a decrease in synaptic strength between synaptically coupled layer 2/3 cortical pyramidal neurons. Using quantal analysis and mEPSP analysis, we demonstrate that a lowered extracellular Ca2+ produces a reduction in the postsynaptic quantal size in addition to its known effect on release probability. An elevated Mg2+ level can prevent this reduction in postsynaptic efficacy at subphysiological Ca2+ levels. We show that the calcium-dependent effect on postsynaptic quantal size is mediated by group 1 metabotropic glutamate receptors, acting via CaMKII (Ca2+/calmodulin-dependent protein kinase II) and PKC. Therefore, physiologically relevant changes in extracellular Ca2+ can regulate information transfer at cortical synapses via both presynaptic and postsynaptic mechanisms

SOX9 transduction of a human chondrocytic cell line identifies novel genes regulated in primary human chondrocytes and in osteoarthritis

The transcription factor SOX9 is important in maintaining the chondrocyte phenotype. To identify novel genes regulated by SOX9 we investigated changes in gene expression by microarray analysis following retroviral transduction with SOX9 of a human chondrocytic cell line (SW1353). From the results the expression of a group of genes (SRPX, S100A1, APOD, RGC32, CRTL1, MYBPH, CRLF1 and SPINT1) was evaluated further in human articular chondrocytes (HACs). First, the same genes were investigated in primary cultures of HACs following SOX9 transduction, and four were found to be similarly regulated (SRPX, APOD, CRTL1 and S100A1). Second, during dedifferentiation of HACs by passage in monolayer cell culture, during which the expression of SOX9 progressively decreased, four of the genes (S100A1, RGC32, CRTL1 and SPINT1) also decreased in their expression. Third, in samples of osteoarthritic (OA) cartilage, which had decreased SOX9 expression compared with age-matched controls, there was decreased expression of SRPX, APOD, RGC32, CRTL1 and SPINT1. The results showed that a group of genes identified as being upregulated by SOX9 in the initial SW1353 screen were also regulated in expression in healthy and OA cartilage. Other genes initially identified were differently expressed in isolated OA chondrocytes and their expression was unrelated to changes in SOX9. The results thus identified some genes whose expression appeared to be linked to SOX9 expression in isolated chondrocytes and were also altered during cartilage degeneration in osteoarthritis

Functional properties of in vitro excitatory cortical neurons derived from human pluripotent stem cells

The in vitro derivation of regionally defined human neuron types from patient‐derived stem cells is now established as a resource to investigate human development and disease. Characterization of such neurons initially focused on the expression of developmentally regulated transcription factors and neural markers, in conjunction with the development of protocols to direct and chart the fate of differentiated neurons. However, crucial to the understanding and exploitation of this technology is to determine the degree to which neurons recapitulate the key functional features exhibited by their native counterparts, essential for determining their usefulness in modelling human physiology and disease in vitro. Here, we review the emerging data concerning functional properties of human pluripotent stem cell‐derived excitatory cortical neurons, in the context of both maturation and regional specificity. [Image: see text

Prognostic impact and the relevance of PTEN copy number alterations in patients with advanced colorectal cancer (CRC) receiving bevacizumab

Article first published online: 25 MAR 2013Loss of phosphatase and tensin homologue (PTEN) expression may be prognostic in colorectal cancer (CRC) and may have a correlation with vascular endothelial growth factor (VEGF) expression via hypoxia-inducible factor 1 (HIF-1) alpha, and the PI3K/mTOR pathways. We therefore have explored the prognostic association of PTEN loss and the potential that PTEN loss may be predictive of outcome with bevacizumab. Patients enrolled in the AGITG MAX trial, a randomized Phase III trial of capecitabine (C) +/− bevacizumab (B) (+/− mitomycin C [M]) with available tissues were analyzed for PTEN expression (loss vs. no loss) as assessed using a Taqman® copy number assay (CNA). Of the original 471 patients enrolled, tissues from 302 (64.1%) patients were analyzed. PTEN loss was observed in 38.7% of patients. There was no relationship between PTEN loss and KRAS or BRAF mutation. PTEN status was not prognostic for progression-free survival (PFS) or overall survival (OS) in multivariate analyses adjusting for other baseline factors; loss versus no loss PFS hazard ratio (HR) 0.9 (0.7–1.16), OS HR 1.04 (0.79–1.38). PTEN was not prognostic when assessed by KRAS and BRAF status. By using the comparison of C versus CB+CBM, PTEN status was not significantly predictive of the effectiveness of B for PFS or OS. PTEN status was not prognostic for survival in advanced colorectal cancer, irrespective of KRAS or BRAF status. PTEN status did not significantly predict different benefit with bevacizumb therapy.Timothy J. Price, Jennifer E. Hardingham, Chee K. Lee, Amanda R. Townsend, Joseph W. Wrin, Kate Wilson, Andrew Weickhardt, Robert J. Simes, Carmel Murone & Niall C. Tebbut

Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

<p>Abstract</p> <p>Background</p> <p>In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types.</p> <p>Results</p> <p>Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border.</p> <p>Conclusion</p> <p>Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.</p

Can we accurately report PTEN status in advanced colorectal cancer?

BACKGROUND: Loss of phosphatase and tensin homologue (PTEN) function evaluated by loss of PTEN protein expression on immunohistochemistry (IHC) has been reported as both prognostic in metastatic colorectal cancer and predictive of response to anti-EGFR monoclonal antibodies although results remain uncertain. Difficulties in the methodological assessment of PTEN are likely to be a major contributor to recent conflicting results. METHODS: We assessed loss of PTEN function in 51 colorectal cancer specimens using Taqman® copy number variation (CNV) and IHC. Two blinded pathologists performed independent IHC assessment on each specimen and inter-observer variability of IHC assessment and concordance of IHC versus Taqman® CNV was assessed. RESULTS: Concordance between pathologists (PTEN loss vs no loss) on IHC assessment was 37/51 (73%). In specimens with concordant IHC assessment, concordance between IHC and Taqman® copy number in PTEN loss assessment was 25/37 (68%). CONCLUSION: Assessment PTEN loss in colorectal cancer is limited by the inter-observer variability of IHC, and discordance of CNV with loss of protein expression. An understanding of the genetic mechanisms of PTEN loss and implementation of improved and standardized methodologies of PTEN assessment are required to clarify the role of PTEN as a biomarker in colorectal cancer