Reduced hippocampal LTP and spatial learning in mice lacking NMDA receptor epsilon 1 subunit

The NMDA (N-methyl-D-aspartate) receptor channel is important for synaptic plasticity, which is thought to underlie learning, memory and development. The NMDA receptor channel is formed by at least two members of the glutamate receptor (GluR) channel subunit families, the GluR epsilon (NR2) and GluR zeta (NR1) subunit families. The four epsilon subunits are distinct in distribution, properties and regulation. On the basis of the Mg2+ sensitivity and expression patterns, we have proposed that the epsilon 1 (NR2A) and epsilon 2 (NR2B) subunits play a role in synaptic plasticity. Here we show that targeted disruption of the mouse epsilon 1 subunit gene resulted in significant reduction of the NMDA receptor channel current and long-term potentiation at the hippocampal CA1 synapses. The mutant mice also showed a moderate deficiency in spatial learning. These results support the notion that the NMDA receptor channel-dependent synaptic plasticity is the cellular basis of certain forms of learning.

Developmental changes in distribution of NMDA receptor channel subunit mRNAs

In situ hybridization analyses have revealed drastic changes in expression and distribution of five subunit mRNAs of the mouse NMDA receptor channel during brain development. The epsilon 1 subunit mRNA is expressed postnatally and widely in the brain. On the other hand, the epsilon 2 subunit mRNA is found throughout the entire embryonic brain, but its expression becomes restricted to the forebrain at postnatal stages. The epsilon 3 subunit mRNA appears postnatally and predominantly in the cerebellum, whereas the epsilon 4 subunit mRNA is abundantly expressed in the diencephalon and the brainstem at embryonic and neonatal stages. In contrast, the zeta 1 subunit mRNA distributes ubiquitously in the brain throughout development. These findings suggest that changes in the subunit composition of the NMDA receptor channel take place during brain development.

Impairment of motor coordination, Purkinje cell synapse formation, and cerebellar long-term depression in GluR delta 2 mutant mice

Of the six glutamate receptor (GluR) channel subunit families identified by molecular cloning, five have been shown to constitute either the AMPA, kainate, or NMDA receptor channel, whereas the function of the delta subunit family remains unknown. The selective localization of the delta 2 subunit of the GluR delta subfamily in cerebellar Purkinje cells prompted us to examine its possible physiological roles by the gene targeting technique. Analyses of the GluR delta 2 mutant mice reveal that the delta 2 subunit plays important roles in motor coordination, formation of parallel fiber-Purkinje cell synapses and climbing fiber-Purkinje cell synapses, and long-term depression of parallel fiber-Purkinje cell synaptic transmission. These results suggest a close relationship between synaptic plasticity and synapse formation in the cerebellum.

Impairment of suckling response, trigeminal neuronal pattern formation, and hippocampal LTD in NMDA receptor epsilon 2 subunit mutant mice

Multiple epsilon subunits are major determinants of the NMDA receptor channel diversity. Based on their functional properties in vitro and distributions, we have proposed that the epsilon 1 and epsilon 2 subunits play a role in synaptic plasticity. To investigate the physiological significance of the NMDA receptor channel diversity, we generated mutant mice defective in the epsilon 2 subunit. These mice showed no suckling response and died shortly after birth but could survive by hand feeding. The mutation hindered the formation of the whisker-related neuronal barrelette structure and the clustering of primary sensory afferent terminals in the brainstem trigeminal nucleus. In the hippocampus of the mutant mice, synaptic NMDA responses and longterm depression were abolished. These results suggest that the epsilon 2 subunit plays an essential role in both neuronal pattern formation and synaptic plasticity.

Pathogenesis of Chiari malformation: a morphometric study of the posterior cranial fossa

To investigate overcrowding in the posterior cranial fossa as the pathogenesis of adult-type Chiari malformation, the authors studied the morphology of the brainstem and cerebellum within the posterior cranial fossa (neural structures consisting of the midbrain, pons, cerebellum, and medulla oblongata) as well as the base of the skull while taking into consideration their embryological development. Thirty patients with Chiari malformation and 50 normal control subjects were prospectively studied using neuroimaging. To estimate overcrowding, the authors used a "volume ratio" in which volume of the posterior fossa brain (consisting of the midbrain, pons, cerebellum, and medulla oblongata within the posterior cranial fossa) was placed in a ratio with the volume of the posterior fossa cranium encircled by bony and tentorial structures. Compared to the control group, in the Chiari group there was a significantly larger volume ratio, the two occipital enchondral parts (the exocciput and supraocciput) were significantly smaller, and the tentorium was pronouncedly steeper. There was no significant difference in the posterior fossa brain volume or in the axial lengths of the hindbrain (the brainstem and cerebellum). In six patients with basilar invagination the medulla oblongata was herniated, all three occipital enchondral parts (the basiocciput, exocciput, and supraocciput) were significantly smaller than in the control group, and the volume ratio was significantly larger than that in the Chiari group without basilar invagination. These results suggest that in adult-type Chiari malformation an underdeveloped occipital bone, possibly due to underdevelopment of the occipital somite originating from the paraxial mesoderm, induces overcrowding in the posterior cranial fossa, which contains the normally developed hindbrain. Basilar invagination is associated with a more severe downward herniation of the hindbrain due to the more severely underdeveloped occipital enchondrium, which further exacerbates overcrowding of the posterior cranial fossa.

Association of structural polymorphisms in the human period3 gene with delayed sleep phase syndrome

Recent progress in biological clock research has facilitated genetic analysis of circadian rhythm sleep disorders, such as delayed sleep phase syndrome (DSPS) and non-24-h sleep-wake syndrome (N-24). We analyzed the human period3 (hPer3) gene, one of the human homologs of the Drosophila clock-gene period (Per), as a possible candidate for rhythm disorder susceptibility. All of the coding exons in the hPer3 gene were screened for polymorphisms by a PCR-based strategy using genomic DNA samples from sleep disorder patients and control subjects. We identified six sequence variations with amino acid changes, of which five were common and predicted four haplotypes of the hPer3 gene. One of the haplotypes was significantly associated with DSPS (Bonferroni's corrected P = 0.037; odds ratio = 7.79; 95% CI 1.59-38.3) in our study population. Our results suggest that structural polymorphisms in the hPer3 gene may be implicated in the pathogenesis of DSPS.

Immunologic 'ignorance' of vascularized organ transplants in the absence of secondary lymphoid tissue

Secondary lymphoid organs (the spleen, lymph nodes and mucosal lymphoid tissues) provide the proper environment for antigen-presenting cells to interact with and activate naive T and B lymphocytes. Although it is generally accepted that secondary lymphoid organs are essential for initiating immune responses to microbial antigens and to skin allografts, the prevailing view has been that the immune response to primarily vascularized organ transplants such as hearts and kidneys does not require the presence of secondary lymphoid tissue. The assumption has been that the immune response to such organs is initiated in the graft itself when recipient lymphocytes encounter foreign histocompatibility antigens presented by the graft's endothelial cells. In contrast to this view, we show here that cardiac allografts are accepted indefinitely in recipient mice that lack secondary lymphoid tissue, indicating that the alloimmune response to a vascularized organ transplant cannot be initiated in the graft itself. Moreover, we demonstrate that the permanent acceptance of these grafts is not due to tolerance but is because of immunologic 'ignorance'.

Nintedanib in patients with progressive fibrosing interstitial lung diseases-subgroup analyses by interstitial lung disease diagnosis in the INBUILD trial: a randomised, double-blind, placebo-controlled, parallel-group trial

BACKGROUND

The INBUILD trial investigated the efficacy and safety of nintedanib versus placebo in patients with progressive fibrosing interstitial lung diseases (ILDs) other than idiopathic pulmonary fibrosis (IPF). We aimed to establish the effects of nintedanib in subgroups based on ILD diagnosis.

METHODS

The INBUILD trial was a randomised, double-blind, placebo-controlled, parallel group trial done at 153 sites in 15 countries. Participants had an investigator-diagnosed fibrosing ILD other than IPF, with chest imaging features of fibrosis of more than 10% extent on high resolution CT (HRCT), forced vital capacity (FVC) of 45% or more predicted, and diffusing capacity of the lung for carbon monoxide (DLco) of at least 30% and less than 80% predicted. Participants fulfilled protocol-defined criteria for ILD progression in the 24 months before screening, despite management considered appropriate in clinical practice for the individual ILD. Participants were randomly assigned 1:1 by means of a pseudo-random number generator to receive nintedanib 150 mg twice daily or placebo for at least 52 weeks. Participants, investigators, and other personnel involved in the trial and analysis were masked to treatment assignment until after database lock. In this subgroup analysis, we assessed the rate of decline in FVC (mL/year) over 52 weeks in patients who received at least one dose of nintedanib or placebo in five prespecified subgroups based on the ILD diagnoses documented by the investigators: hypersensitivity pneumonitis, autoimmune ILDs, idiopathic non-specific interstitial pneumonia, unclassifiable idiopathic interstitial pneumonia, and other ILDs. The trial has been completed and is registered with ClinicalTrials.gov, number NCT02999178.

FINDINGS

Participants were recruited between Feb 23, 2017, and April 27, 2018. Of 663 participants who received at least one dose of nintedanib or placebo, 173 (26%) had chronic hypersensitivity pneumonitis, 170 (26%) an autoimmune ILD, 125 (19%) idiopathic non-specific interstitial pneumonia, 114 (17%) unclassifiable idiopathic interstitial pneumonia, and 81 (12%) other ILDs. The effect of nintedanib versus placebo on reducing the rate of FVC decline (mL/year) was consistent across the five subgroups by ILD diagnosis in the overall population (hypersensitivity pneumonitis 73·1 [95% CI -8·6 to 154·8]; autoimmune ILDs 104·0 [21·1 to 186·9]; idiopathic non-specific interstitial pneumonia 141·6 [46·0 to 237·2]; unclassifiable idiopathic interstitial pneumonia 68·3 [-31·4 to 168·1]; and other ILDs 197·1 [77·6 to 316·7]; p=0·41 for treatment by subgroup by time interaction). Adverse events reported in the subgroups were consistent with those reported in the overall population.

INTERPRETATION

The INBUILD trial was not designed or powered to provide evidence for a benefit of nintedanib in specific diagnostic subgroups. However, its results suggest that nintedanib reduces the rate of ILD progression, as measured by FVC decline, in patients who have a chronic fibrosing ILD and progressive phenotype, irrespective of the underlying ILD diagnosis.

FUNDING

Boehringer Ingelheim.

Motor discoordination and increased susceptibility to cerebellar injury in GLAST mutant mice

To study the function of GLAST, a glutamate transporter highly expressed in the cerebellar Bergmann astrocytes, the mouse GLAST gene was inactivated. GLAST-deficient mice developed normally and could manage simple coordinated tasks, such as staying on a stationary or a slowly rotating rod, but failed more challenging task such as staying on a quickly rotating rod. Electrophysiological examination revealed that Purkinje cells in the mutant mice remained to be multiply innervated by climbing fibres even at the adult stage. We also found that oedema volumes in the mutant mice increased significantly after cerebellar injury. These results indicate that GLAST plays active roles both in the cerebellar climbing fibre synapse formation and in preventing excitotoxic cerebellar damage after acute brain injury.

Impaired synapse elimination during cerebellar development in PKC gamma mutant mice

PKC gamma is highly expressed in Purkinje cells (PCs) but not in other types of neurons in the cerebellum. The expression of PKC gamma changes markedly during cerebellar development, being very low at birth and reaching a peak around the third postnatal week. This temporal pattern of PKC gamma expression coincides with the developmental transition from multiple to single climbing fiber innervation onto each PC. In adult mutant mice deficient in PKC gamma, we found that 41% of PCs are still innervated by multiple climbing fibers, while other aspects of the cerebellum including the morphology and excitatory synaptic transmission of PCs appear normal. Thus, elimination of multiple climbing fiber innervation appears to be specifically impaired in the mutant cerebellum. We suggest that the developmental role of PKC gamma may be to act as a downstream element in the signal cascade necessary for the elimination of surplus climbing fiber synapses.

Prevention of acute liver failure in rats with reversibly immortalized human hepatocytes

Because of a critical shortage in suitable organs, many patients with terminal liver disease die each year before liver transplantation can be performed. Transplantation of isolated hepatocytes has been proposed for the temporary metabolic support of patients awaiting liver transplantation or spontaneous reversion of their liver disease. A major limitation of this form of therapy is the present inability to isolate an adequate number of transplantable hepatocytes. A highly differentiated cell line, NKNT-3, was generated by retroviral transfer in normal primary adult human hepatocytes of an immortalizing gene that can be subsequently and completely excised by Cre/Lox site-specific recombination. When transplanted into the spleen of rats under transient immunosuppression, reversibly immortalized NKNT-3 cells provided life-saving metabolic support during acute liver failure induced by 90% hepatectomy.

Solvolytic desulfation of glycosaminoglycuronan sulfates with dimethyl sulfoxide containing water or methanol

A solvolytic desulfation of glycosaminoglycuronan sulfates was developed by treatment of their pyridinium salts with dimethyl sulfoxide containing 10% of water or methanol at 80-100 degrees. Chemical and physical studies showed that the solvolytic desulfation is a useful method applicable to all the known glycosaminoglycuronan sulfates without producing depolymerization or unfavorable chemical changes in the polysaccharide molecules. An almost completely desulfated, N-acetylated heparin (S: 0.12%) was obtained by treatment of an N-desulfated and N-acetylated heparin with dimethyl sulfoxide containing 10% of methanol for 2 h at 100 degrees.

Ruthenium complex-catalyzed direct ortho arylation and alkenylation of 2-arylpyridines with organic halides

[reaction: see text] The ortho position of the aromatic ring of pyridyl group-substituted aromatic compounds is directly arylated or alkenylated with organic halides in the presence of a catalytic amount of a ruthenium(II)-phosphine complex.

Selective scarcity of NMDA receptor channel subunits in the stratum lucidum (mossy fibre-recipient layer) of the mouse hippocampal CA3 subfield

Hippocampal synapses express two distinct forms of the long-term potentiation (LTP), i.e. NMDA receptor-dependent and -independent LTPs. To understand its molecular-anatomical basis, we produced affinity-purified antibodies against the GluRepsilon1 (NR2A), GluRepsilon2 (NR2B), and GluRzeta1 (NR1) subunits of the N-methyl-D-aspartate (NMDA) receptor channel, and determined their distributions in the mouse hippocampus. Using NMDA receptor subunit-deficient mice as the specificity controls, section pretreatment with proteases (pepsin and proteinase K) was found to be very effective to detect authentic NMDA receptor subunits. As the result of modified immunohistochemistry, all three subunits were detected at the highest level in the strata oriens and radiatum of the CA1 subfield, and high levels were also seen in most other neuropil layers of the CA1 and CA3 subfields and of the dentate gyrus. However, the stratum lucidum, a mossy fibre-recipient layer of the CA3 subfield, contained low levels of the GluRepsilon1 and GluRzeta1 subunits and almost excluded the GluRepsilon2 subunit. Double immunofluorescence with the AMPA receptor GluRalpha1 (GluR1 or GluR-A) subunit further demonstrated that the GluRepsilon1 subunit was colocalized in a subset, not all, of GluRalpha1-immunopositive structures in the stratum lucidum. Therefore, the selective scarcity of these NMDA receptor subunits in the stratum lucidum suggests that a different synaptic targeting mechanism exerts within a single CA3 pyramidal neurone in vivo, which would explain contrasting significance of the NMDA receptor channel in LTP induction mechanisms between the mossy fibre-CA3 synapse and other hippocampal synapses.

Distinct distributions of five N-methyl-D-aspartate receptor channel subunit mRNAs in the forebrain

The distributions of five NMDA receptor channel subunit mRNAs in the mouse forebrain at postnatal day 21 were semiquantitatively examined by in situ hybridization with subunit-specific oligonucleotide probes. In contrast to ubiquitous distribution of the zeta 1 subunit mRNA throughout the forebrain, distributions of four epsilon subunit mRNAs were highly variable from nucleus to nucleus. The telencephalon (except for the septum) expressed the epsilon 1 and epsilon 2 subunit mRNAs. Various combinations of the epsilon 1, epsilon 2, epsilon 3, and epsilon 4 subunit mRNAs were present in different nuclei of the septum, the olfactory bulb, and the thalamus. In the hypothalamus, the suprachiasmatic nucleus expressed distinct signals for the epsilon 3 subunit mRNA alone, whereas other nuclei showed faint signals for the epsilon 1, epsilon 2, and epsilon 4 subunit mRNAs. Moreover, different signal levels of the epsilon subunit mRNAs were found in various regions. The hippocampal CA1 region expressed higher signals for the epsilon 1 and epsilon 2 subunit mRNAs than the CA3 region and the dentate gyrus. In the cerebral cortex, signal levels of the epsilon 1 subunit mRNA were higher in the laminae II/III, IV, and VI than the lamina V, whereas those of the epsilon 2 subunit mRNA were highest in laminae II/III and lowest in laminae IV and V. Different signal levels between the epsilon 1 and epsilon 2 subunit mRNAs were also discerned in the amygdala, the caudate-putamen, and the thalamus. The distinct anatomical distributions and differential signal levels of the epsilon subunit mRNAs strongly suggest different subunit organizations of the NMDA receptor channel in different forebrain neurons, which may result in functional diversity of the channel in vivo.

Persistent multiple climbing fiber innervation of cerebellar Purkinje cells in mice lacking mGluR1

Most of the cerebellar Purkinje cells (PCs) of an adult animal are innervated individually by a single climbing fiber (CF) that forms strong excitatory synapses with the PCs. This one-to-one relationship between a PC and a CF is a consequence of a developmentally regulated regression of the innervation of PCs by CFs. We found that, in mice deficient in the type 1 metabotropic glutamate receptor (mGluR1), the regression of supernumerary CFs ceases by the end of the second postnatal week, which is about one week earlier than in normal mice. Consequently, about one third of PCs in the mGluR1 mutant mice are innervated by multiple CFs in adulthood. We conclude that the regression of CFs normally occurs in two developmental phases and that mGluR1 plays a crucial role in the second phase.

Estimates of the cost-effectiveness of a single course of interferon-alpha 2b in patients with histologically mild chronic hepatitis C

BACKGROUND

Chronic hepatitis C is a major cause of illness and death in the United States. Interferon-alpha 2b can induce clinical, biochemical, and virologic remission in some patients with chronic hepatitis C, but the long-term cost-effectiveness of this treatment, particularly in patients with histologically mild disease, is unknown.

OBJECTIVE

To estimate the cost-effectiveness of interferon-alpha 2b in mild chronic hepatitis C.

DESIGN

Meta-analysis of five prospective trials and cost-effectiveness analysis. Projection of the clinical and economic outcomes expected from loss of hepatitis C virus was done by using a Markov simulation. The potential effect of uncertainty in the model assumptions was tested by using sensitivity analyses.

DATA SOURCES

Search of the MEDLINE database, opinions of expert panels, hospital cost data, and adjusted physician charges.

PATIENTS

Hypothetical cohorts with histologically mild chronic hepatitis C.

INTERVENTION

The model assumed a single 6-month course of recombinant interferon-alpha 2b.

MEASUREMENTS

Life expectancy, quality-adjusted life expectancy, costs, and marginal cost-effectiveness ratios from a managed care perspective.

RESULTS

In 27% of patients with mild chronic hepatitis C treated with interferon-alpha 2b for 6 months, serum alanine aminotransferase levels permanently returned to normal and viral status remained negative. The model estimated that interferon-alpha 2b treatment in this population should increase life expectancy by 3.1 years if given at 20 years of age, by 1.5 years at 35 years of age, and by 22 days at 70 years of age; discounted marginal cost-effectiveness ratios are $500, $1900, and $62,000 per year of life gained, respectively. Varying the long-term response rates and progression rates for mild and moderate chronic hepatitis to near zero in sensitivity analyses substantially affected the results: Ratios ranged from $31,000 for a 20-year-old patient to $640,000 for a 70-year-old patient.

CONCLUSIONS

On the basis of estimations in this mathematical model of the natural history of chronic hepatitis C, treating mild chronic hepatitis with interferon-alpha 2b should prolong life expectancy at a reasonable marginal cost per year of life gained, particularly in younger patients.

Selective expression of the glutamate receptor channel delta 2 subunit in cerebellar Purkinje cells

The primary structure of a putative subunit of the mouse glutamate receptor channel, designated as the delta 2 subunit, has been deduced by cloning and sequencing the cDNA. The delta 2 subunit has four putative transmembrane segments characteristic for neurotransmitter-gated ion channels, and shares 56% amino acid sequence identity with the delta 1 subunit of the mouse glutamate receptor channel and 14-24% identity with the subunits of the AMPA-, kainate- or NMDA-selective glutamate receptor channel. RNA blot and in situ hybridization analyses show that the delta 2 subunit mRNA is localized in cerebellar Purkinje cells. Furthermore, immunoblot and immunohistochemical analyses suggest that the delta 2 subunit protein is actually expressed in vivo in Purkinje neurons. The selective localization of the delta 2 subunit in Purkinje cells may imply a role of the delta 2 subunit in Purkinje cell-specific function such as the cerebellar LTD.

Cloning and expression of the epsilon 4 subunit of the NMDA receptor channel

The primary structure of a novel subunit of the mouse NMDA (N-methyl-D-aspartate) receptor channel, designated epsilon 4, has been revealed by cloning and sequencing the cDNA. The epsilon 4 subunit shares high amino acid sequence identity with the epsilon 1, epsilon 2 and epsilon 3 subunits of the mouse NMDA receptor channel, thus constituting the epsilon subfamily of the glutamate receptor channel. Expression from cloned cDNAs of the epsilon 4 subunit together with the zeta 1 subunit in Xenopus oocytes yields functional NMDA receptor channels. The epsilon 4/zeta 1 heteromeric channel exhibits high apparent affinities for agonists and low sensitivities to competitive antagonists. The epsilon 4 subunit is thus distinct in functional properties from the epsilon 1, epsilon 2 and epsilon 3 subunits, and contributes further diversity of the NMDA receptor channel.

Impaired motor coordination and persistent multiple climbing fiber innervation of cerebellar Purkinje cells in mice lacking Galphaq

Mice lacking the alpha-subunit of the heterotrimeric guanine nucleotide binding protein Gq (Galphaq) are viable but suffer from ataxia with typical signs of motor discoordination. The anatomy of the cerebellum is not overtly disturbed, and excitatory synaptic transmission from parallel fibers to cerebellar Purkinje cells (PCs) and from climbing fibers (CFs) to PCs is functional. However, about 40% of adult Galphaq mutant PCs remain multiply innervated by CFs because of a defect in regression of supernumerary CFs in the third postnatal week. Evidence is provided suggesting that Galphaq is part of a signaling pathway that is involved in the elimination of multiple CF innervation during this period.

Structural organization of the human vitamin D receptor chromosomal gene and its promoter

The vitamin D receptor (VDR) is known to mediate the pleiotropic biological actions of 1,25-dihydroxyvitamin D3 through its ability to modulate the expression of target genes. The regulation of this ligand-activated cellular transcription factor is reported to occur at both transcriptional and posttranslational levels. To begin to address the molecular basis by which the VDR gene is regulated transcriptionally, we report here an initial characterization of the human VDR gene and its promoter. We isolated several overlapping A-phage and cosmid clones that cover more than 100 kb of human DNA and contained the entire VDR gene. The gene is comprised of 11 exons that, together with intervening introns, span approximately 75 kb. The noncoding 5'-end of the gene includes exons 1A, 1B, and 1C. Eight additional exons (exons 2-9) encode the structural portion of the VDR gene product. While primer extension and S1 nuclease-mapping studies reveal several common transcriptional start sites, three unique mRNA species are produced as a result of the differential splicing of exons 1B and 1C. The DNA sequence lying upstream of exon 1A is GC rich and does not contain an apparent TATA box. Several potential binding sites for the transcription factor SP1 and other activators are evident. Fusion of DNA fragments containing putative promoter sequences upstream of the luciferase structural gene followed by transient transfection of these plasmids into several mammalian cell lines resulted in significant reporter activity. Due to the size and complexity of the 5'-end of the VDR gene, we examined the activity of a DNA fragment surrounding exon 1C. An intron fragment 3' of exon 1C conferred retinoic acid responsivity when fused to a reporter gene plasmid, suggesting a molecular mechanism for the previously observed ability of retinoic acid to induce the VDR. The recovery of the gene for the human VDR will enable further studies on the transcriptional regulation of this gene.