Identification of a new murine tumor necrosis factor receptor locus that contains two novel murine receptors for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)

Tumor necrosis factor (TNF) ligand and receptor superfamily members play critical roles in diverse developmental and pathological settings. In search for novel TNF superfamily members, we identified a murine chromosomal locus that contains three new TNF receptor-related genes. Sequence alignments suggest that the ligand binding regions of these murine TNF receptor homologues, mTNFRH1, -2 and -3, are most homologous to those of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors. By using a number of in vitro ligand-receptor binding assays, we demonstrate that mTNFRH1 and -2, but not mTNFRH3, bind murine TRAIL, suggesting that they are indeed TRAIL receptors. This notion is further supported by our demonstration that both mTNFRH1:Fc and mTNFRH2:Fc fusion proteins inhibited mTRAIL-induced apoptosis of Jurkat cells. Unlike the only other known murine TRAIL receptor mTRAILR2, however, neither mTNFRH2 nor mTNFRH3 has a cytoplasmic region containing the well characterized death domain motif. Coupled with our observation that overexpression of mTNFRH1 and -2 in 293T cells neither induces apoptosis nor triggers NFkappaB activation, we propose that the mTnfrh1 and mTnfrh2 genes encode the first described murine decoy receptors for TRAIL, and we renamed them mDcTrailr1 and -r2, respectively. Interestingly, the overall sequence structures of mDcTRAILR1 and -R2 are quite distinct from those of the known human decoy TRAIL receptors, suggesting that the presence of TRAIL decoy receptors represents a more recent evolutionary event.     

Multifaceted genetic analysis of the “Critically Endangered” brush-tailed rock-wallaby Petrogale penicillata in Victoria, Australia: Implications for management

The use of molecular genetic techniques can aidwildlife managers in setting priorities anddevising management strategies for scatteredpopulations of threatened taxa. In this study,six remnant populations of the criticallyendangered brush-tailed rock-wallaby (Petrogale penicillata) in Victoria, Australia,were examined using karyotypic, microsatellite(11 loci) and mitochondrial DNA (mtDNA) controlregion sequence analysis. Each remnantpopulation was found to be genetically distinct(unique microsatellite alleles and controlregion haplotypes), but had low geneticdiversity. This distribution of geneticdiversity between, rather than withinpopulations, is most likely a consequence ofrecent severe reductions in population size anddispersal that have occurred since Europeansettlement. The six mtDNA control regionhaplotypes identified in the Victorianpopulations were all closely related (average1.3% sequence divergence), and only 2%divergence separated haplotypes from EastGippsland and the Grampians (550 km to thewest). In contrast there was considerablesequence divergence (7.7%) between theVictorian haplotypes and those found in P.penicillata from elsewhere in the speciesrange. In comparison, 8.8% divergenceseparates P. penicillata from the closelyrelated P. herberti. The Victorianhaplotypes also formed a distinct and wellsupported monophyletic group that excludedhaplotypes from other P. penicillata andP. herberti. In light of these data, werecommend that the remnant Victorianpopulations of P. penicillata be managedseparately from remaining populations in NewSouth Wales and Queensland; and thatindividuals be regularly exchanged amongst theVictorian populations to increase theirdiversity and reduce the likelihood ofinbreeding depression.     

Effects of High Pressure on Glucose Transport in the Human Erythrocyte

The effects of raised hydraulic pressure on D-glucose exit from human red cells at 25 degrees C were determined using light scattering measurements in a sealed pressurized spectrofluorimeter cuvette. The reduction in the rates of glucose exit with raised pressure provides an index of the activation volume, deltaV++ (delta ln k/deltaP)(T) = -deltaV++/RT. Raised pressure decreased the rate constant of glucose exit from 0.077 +/- 0.003 s(-1) to 0.050 +/- 0.002 s(-1) (n = 5, P < 0.003). The Ki for glucose binding to the external site was 2.7 +/- 0.4 mm (0.1 MPa) and was reduced to 1.45 +/- 0.15 mm (40 MPa), (P < 0.01, Student's t test). Maltose had a biphasic effect on deltaV++. At [maltose] <250 microM, deltaV++ of glucose exit increased above that with [maltose = 0 mM], at >1 mm maltose, deltaV++ was reduced below that with [maltose = 0 mM]. Pentobarbital (2 mM) decreased the deltaV++ of net glucose exit into glucose-free solution from 30 +/- 5 ml mol(-1) (control) to 2 +/- 0.5 ml mol(-1) (P < 0.01). Raised pressure had a negligible effect on L-sorbose exit. These findings suggest that stable hydrated and liganded forms of GLUT with lower affinity towards glucose permit higher glucose mobilities across the transporter and are modelled equally well with one-alternating or a two-fixed-site kinetic models.     

A haplolethal locus uncovered by deletions in the mouse T complex

Proper levels of gene expression are important for normal mammalian development. Typically, altered gene dosage caused by karyotypic abnormalities results in embryonic lethality or birth defects. Segmental aneuploidy can be compatible with life but often results in contiguous gene syndromes. The ability to manipulate the mouse genome allows the systematic exploration of regions that are affected by alterations in gene dosage. To explore the effects of segmental haploidy in the mouse t complex on chromosome 17, radiation-induced deletion complexes centered at the Sod2 and D17Leh94 loci were generated in embryonic stem (ES) cells. A small interval was identified that, when hemizygous, caused specific embryonic lethal phenotypes (exencephaly and edema) in most fetuses. The penetrance of these phenotypes was background dependent. Additionally, evidence for parent-of-origin effects was observed. This genetic approach should be useful for identifying genes that are imprinted or whose dosage is critical for normal embryonic development.     

Aging and surface expression of hippocampal NMDA receptors

Aging is known to alter many physiological processes within the brain including synaptic responses, long-term potentiation, learning, and memory. Aging has also been shown to alter the expression and distribution of N-methyl-d-aspartate (NMDA) receptors in many different brain regions, including the hippocampus. Additionally, we have recently reported that young adult rats show an activity-dependent increase in the surface expression of NMDA receptors. We have extended these observations in the present study in aged animals and have found that aged Fischer 344 rats fail to show activity-dependent changes in the surface distribution of NMDA receptors. In conjunction with this observation we have also noted that aged rats show an expression deficit in the C2 splice variant of the NR1 subunit. This subunit is preferentially shifted to the surface following stimulation in young adult animals. As the NMDA receptor is thought to play an important role in neuronal signaling, these observations suggest possible new areas of dysfunction in this receptor that might underlie age-related deficits in neuronal physiology.     

Visualization of lymphotoxin-beta and lymphotoxin-beta receptor expression in mouse embryos

The heteromeric lymphotoxin alphabeta ligand (LT) binds to the LTbeta receptor (LTbetaR) and provides an essential trigger for lymph node (LN) development. LTbetaR signaling is also critical for the emergence of pathological ectopic lymph node-like structures and the maintenance of an organized splenic white pulp. To better understand the role of LT in development, the expression patterns of LTbeta and LTbetaR mRNA were examined by in situ hybridization in the developing mouse embryo. Images of LTbeta ligand expression in developing peripheral LN in the E18.5 embryo revealed a relatively early phase structure and allowed for comparative staging with LN development in rat and humans. The LTbetaR is expressed from E16.5 onward in respiratory, salivary, bronchial, and gastric epithelium, which may be consistent with early communication events between lymphoid elements and epithelial specialization over emerging mucosal LN. Direct comparison of mouse fetal and adult tissues by FACS analysis confirmed the elevated expression of LTBR in some embryonic epithelial layers. Therefore, surface LTBR expression may be elevated during fetal development in some epithelial layers.     

Eukaryotic elongation factor 1A interacts with the upstream pseudoknot domain in the 3' untranslated region of tobacco mosaic virus RNA

The genomic RNA of tobacco mosaic virus (TMV), like that of other positive-strand RNA viruses, acts as a template for both translation and replication. The highly structured 3' untranslated region (UTR) of TMV RNAs plays an important role in both processes; it is not polyadenylated but ends with a tRNA-like structure (TLS) preceded by a conserved upstream pseudoknot domain (UPD). The TLS of tobamoviral RNAs can be specifically aminoacylated and, in this state, can interact with eukaryotic elongation factor 1A (eEF1A)/GTP with high affinity. Using a UV cross-linking assay, we detected another specific binding site for eEF1A/GTP, within the UPDs of TMV and crucifer-infecting tobamovirus (crTMV), that does not require aminoacylation. A mutational analysis revealed that UPD pseudoknot conformation and some conserved primary sequence elements are required for this interaction. Its possible role in the regulation of tobamovirus gene expression and replication is discussed.     

Lymphotoxin/light,lymphoid microenvironments and autoimmune disease

Much of the efficiency of the immune system is attributed to the high degree of spatial and temporal organization in the secondary lymphoid organs. Signalling through the lymphotoxin (LT) pathway is a crucial element in the maintenance of this organized microenvironment. The effect of altering lymphoid microenvironments on immune responses remains relatively unexplored. Inhibitors of the LT and LIGHT pathways have been shown to reduce disease in a wide range of autoimmune models. This approach has provided a tool to probe the effect of manipulation of the microenvironment on both normal and pathological immune responses.     

Musings on the wanderer: what's new in our understanding of vago-vagal reflexes? III. Activity-dependent plasticity in vago-vagal reflexes controlling the stomach

Vago-vagal reflex circuits modulate digestive functions from the oral cavity to the transverse colon. Previous articles in this series have described events at the level of the sensory receptors encoding the peripheral stimuli, the transmission of information in the afferent vagus, and the conversion of this data within the dorsal vagal complex (DVC) to impulses in the preganglionic efferents. The control by vagal efferents of the postganglionic neurons impinging on the glands and smooth muscles of the target organs has also been illustrated. Here we focus on some of the mechanisms by which these apparently static reflex circuits can be made quite plastic as a consequence of the action of modulatory inputs from other central nervous system sources. A large body of evidence has shown that the neuronal elements that constitute these brain stem circuits have nonuniform properties and function differently according to status of their target organs and the level of activity in critical modulatory inputs. We propose that DVC circuits undergo a certain amount of short-term plasticity that allows the brain stem neuronal elements to act in harmony with neural systems that control behavioral and physiological homeostasis.