Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands

The alpha3 fucosyltransferase, FucT-VII, is one of the key glycosyltransferases involved in the biosynthesis of the sialyl Lewis X (sLex) antigen on human leukocytes. The sialyl Lewis X antigen (NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential component of the recruitment of leukocytes to sites of inflammation, mediating the primary interaction between circulating leukocytes and activated endothelium. In order to characterize the enzymatic properties of the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been expressed in Trichoplusia ni insect cells. The enzyme is capable of synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from 3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors demonstrate that FucT-VII is able to synthesize both di-fucosylated and tri-fucosylated structures from mono- fucosylated precursors, but preferentially fucosylates the distal GlcNAc within a polylactosamine chain. Furthermore, the rate of fucosylation of the internal GlcNAc residues is reduced once fucose has been added to the distal GlcNAc. These results indicate that FucT-VII is capable of generating complex selectin ligands, in vitro , however the order of fucose addition to the lactosamine chain affects the rate of selectin ligand synthesis.      

Bovine mammary gland UDP-GalNAc:GlcNAcbeta-R beta1-->4-N- acetylgalactosaminyltransferase is glycoprotein hormone nonspecific and shows interaction with alpha-lactalbumin

We have identified a novel N -acetylgalactosaminyltransferase activity in lactating bovine mammary gland membranes. Acceptor specificity studies and analysis of products obtained in vitro by 400 MHz1H-NMR spectroscopy revealed that the enzyme catalyses the transfer of N - acetylgalactosamine (GalNAc) from UDP-GalNAc to acceptor substrates carrying a terminal, beta-linked N -acetylglucosamine (GlcNAc) residue and establishes a beta1-->4-linkage forming a GalNAcbeta1-->4GlcNAc ( N, N '-diacetyllactosediamine, lacdiNAc) unit. Therefore, the enzyme can be identified as a UDP-GalNAc:GlcNAcbeta-R beta1-->4-N- acetylgalactosaminyltransferase (beta4-GalNAcT). This enzyme resembles invertebrate beta4-GalNAcT as well as mammalian beta4- galactosyltransferase (beta4-GalT) in acceptor specificity. It can, however, be clearly distinguished from the pituitary hormone-specific beta4-GalNAcT by its incapability of acting with an elevated activity on a glycoprotein substrate carrying a hormone-specific peptide motif. Furthermore, the GalNAcT activity appeared not to be due to a promiscuous action of a beta4-GalT as could be demonstrated by comparing the beta4-GalNAcT and beta4-GalT activities of the mammary gland, bovine colostrum, and purified beta4-GalT, by competition studies with UDP-GalNAc and UDP-Gal, and by use of an anti-beta4-GalT polyclonal inhibiting antibody. Interestingly, under conditions where mammalian beta4-GalT forms with alpha-lactalbumin (alpha-LA) the lactose synthase complex, the mammary gland beta4-GalNAcT was similarly induced by alpha-LA to act on Glc with an increased efficiency yielding the lactose analog GalNAcbeta1-->4Glc. This enzyme thus forms the second example of a mammalian glycosyltransferase the specificity of which can be modified by this milk protein. It is proposed that the mammary gland beta4-GalNAcT functions in the synthesis of lacdiNAc- based, complex-type glycans frequently occurring on bovine milk glycoproteins. The action of this enzyme is to be considered when aiming at the production of properly glycosylated protein biopharmaceuticals in the milk of transgenic dairy animals.      

Sharing gene expression data: an array of options

Sharing of microarray data has many advantages for the scientific and biomedical community, and should be advocated by neuroscience journals. The goals of sharing are manifold, and include improving analysis and confidence in results, and facilitating global comparisons between experiments, while at the same time, not penalizing those who share. The sharing of microarray data poses unique challenges relative to more generic data such as DNA sequences. These challenges are surmountable, and various sharing formats are possible. Centralized non-commercial databases are being developed to facilitate this process.     

A Network Approach to Psychopathology: New Insights into Clinical Longitudinal Data

In the network approach to psychopathology, disorders are conceptualized as networks of mutually interacting symptoms (e.g., depressed mood) and transdiagnostic factors (e.g., rumination). This suggests that it is necessary to study how symptoms dynamically interact over time in a network architecture. In the present paper, we show how such an architecture can be constructed on the basis of time-series data obtained through Experience Sampling Methodology (ESM). The proposed methodology determines the parameters for the interaction between nodes in the network by estimating a multilevel vector autoregression (VAR) model on the data. The methodology allows combining between-subject and within-subject information in a multilevel framework. The resulting network architecture can subsequently be analyzed through network analysis techniques. In the present study, we apply the method to a set of items that assess mood-related factors. We show that the analysis generates a plausible and replicable network architecture, the structure of which is related to variables such as neuroticism; that is, for subjects who score high on neuroticism, worrying plays a more central role in the network. Implications and extensions of the methodology are discussed.     

Disorders of attention: a frontier in neuropsychology

There is an extensive behavioural neurological literature on so-called unilateral attentional disorders, but a striking paucity of papers on global disorders of attention, i.e. confusional states. However, confusional states are distinctive because: (1) they are the most common disturbance of the higher functions in clinical practice, by orders of magnitude; (2)they are the only disturbance of the higher functions from which all normal subjects have suffered; (3) they have characteristic clinical manifestations; (4) they are frequently misdiagnosed as progressive dementias, aphasia, memory disorders, and psychoses; (5) they are the only disturbance of the higher functions that commonly cause patients to produce statement that appear to be extremely witty; (6) they can be readily studied experimentally; (7) they are the most common cause of unconcern with or denial of illness. There are almost certainly several different forms of confusional state depending on the aetiology, the rate of development, the age, and the anatomical systems involved, but little classification has yet been carried on. Confusional states are most simply defined as disorders in which there is a loss of the normal coherence of thought or action. Among the striking clinical features are: (1) failure to pay attention, excessive distractibility, or failure to shift attention; (2) paramnesias, i.e. distortions of memory; (3) reduplicative phenomena, 'wild' paraphasias with 'propagation' of error, alterations of mood in many different directions; (4) isolated or predominant disturbance of writing (the most common cause of pur agraphia); (5) unconcern with or denial of illness; (6) apparently playful behaviour. While confusional states are usually attributed to 'global involvement of the brain' as a result of metabolic or toxic disorder, there are in fact many cases produced by focal infarctions inthe right hemisphere, which, in the experience of my department, is one of the commonest effects of cerebrovascular disease. Brief reference is made to the prognosis, and to the theoretical significance for cerebral dominance and the evolutionary development of cerebral dominance in non-human species.     

An Epigenetic Signature in Peripheral Blood Associated with the Haplotype on 17q21.31, a Risk Factor for Neurodegenerative Tauopathy

Little is known about how changes in DNA methylation mediate risk for human diseases including dementia. Analysis of genome-wide methylation patterns in patients with two forms of tau-related dementia – progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD) – revealed significant differentially methylated probes (DMPs) in patients versus unaffected controls. Remarkably, DMPs in PSP were clustered within the 17q21.31 region, previously known to harbor the major genetic risk factor for PSP. We identified and replicated a dose-dependent effect of the risk-associated H1 haplotype on methylation levels within the region in blood and brain. These data reveal that the H1 haplotype increases risk for tauopathy via differential methylation at that locus, indicating a mediating role for methylation in dementia pathophysiology.     

Uveal Melanoma Metastatic to the Liver: The Role of Quantitative Volumetric Contrast-Enhanced MR Imaging in the Assessment of Early Tumor Response after Transarterial Chemoembolization

PURPOSETo determine whether volumetric changes of enhancement as seen on contrast-enhanced magnetic resonance (MR) imaging can help assess early tumor response and predict survival in patients with metastatic uveal melanoma after one session of transarterial chemoembolization (TACE).MATERIALS AND METHODSFifteen patients with 59 lesions who underwent MR imaging before and 3 to 4 weeks after the first TACE were retrospectively included. MR analysis evaluated signal intensities, World Health Organization (WHO), Response Evaluation Criteria in Solid Tumors (RECIST), European Association for the Study of the Liver (EASL), modified RECIST (mRECIST), tumor volume [volumetric RECIST (vRECIST)], and volumetric tumor enhancement [quantitative EASL (qEASL)]. qEASL was expressed in cubic centimeters [qEASL (cm³)] and as a percentage of the tumor volume [qEASL (%)]. Paired t test with its exact permutation distribution was used to compare measurements before and after TACE. The Kaplan-Meier method with the log-rank test was used to calculate overall survival for responders and non-responders.RESULTSIn target lesions, mean qEASL (%) decreased from 63.9% to 42.6% (P = .016). No significant changes were observed using the other response criteria. In non-target lesions, mean WHO, RECIST, EASL, mRECIST, vRECIST, and qEASL (cm³) were significantly increased compared to baseline. qEASL (%) remained stable (P = .214). Median overall survival was 5.6 months. qEASL (cm³) was the only parameter that could predict survival based on target lesions (3.6 vs 40.5 months, P < .001) or overall (target and non-target lesions) response (4.4 vs 40.9 months, P = .001).CONCLUSIONVolumetric tumor enhancement may be used as a surrogate biomarker for survival prediction in patients with uveal melanoma after the first TACE.