Investigation of the function of the LNX family of E3 ubiquitin ligases in the nervous system

The Lnx1 (Ligand of Numb protein X 1) and Lnx2 genes belong to a family of PDZ domain-containing RING finger domain E3 ubiquitin ligases. mRNA expression for both genes have been reported in early murine central nervous system. However, there have been limited reports with regards to the expression patterns for both the proteins in vivo. Hence, we have attempted to characterize the significance of these proteins in the context of morphology and physiology of the central nervous system. Through our studies, we have attempted to examine closely the expression of these two genes in the murine central nervous system. We have also looked at novel interacting ligands for both proteins. Interacting partners have been examined with particular relevance to possible roles of their interactions with LNX1 and LNX2 in the functioning of the nervous system. Moreover, we have performed loss-of-function studies by way of creation and characterization of knockout mice.

Folate regulation of axonal regeneration in the rodent central nervous system through DNA methylation.

The folate pathway plays a crucial role in the regeneration and repair of the adult CNS after injury. Here, we have shown in rodents that such repair occurs at least in part through DNA methylation. In animals with combined spinal cord and sciatic nerve injury, folate-mediated CNS axon regeneration was found to depend on injury-related induction of the high-affinity folate receptor 1 (Folr1). The activity of folate was dependent on its activation by the enzyme dihydrofolate reductase (Dhfr) and a functional methylation cycle. The effect of folate on the regeneration of afferent spinal neurons was biphasic and dose dependent and correlated closely over its dose range with global and gene-specific DNA methylation and with expression of both the folate receptor Folr1 and the de novo DNA methyltransferases. These data implicate an epigenetic mechanism in CNS repair. Folic acid and possibly other nontoxic dietary methyl donors may therefore be useful in clinical interventions to promote brain and spinal cord healing. If indeed the benefit of folate is mediated by epigenetic mechanisms that promote endogenous axonal regeneration, this provides possible avenues for new pharmacologic approaches to treating CNS injuries.

The Representation of Emotion in Autonomic and Central Nervous System Activity

Phenomenologically, humans effectively label and report feeling distinct emotions, yet the extent to which emotions are represented categorically in nervous system activity is controversial. Theoretical accounts differ in this regard, some positing distinct emotional experiences emerge from a dimensional representation (e.g., along axes of valence and arousal) whereas others propose emotions are natural categories, with dedicated neural bases and associated response profiles. This dissertation aims to empirically assess these theoretical accounts by examining how emotions are represented (either as disjoint categories or as points along continuous dimensions) in autonomic and central nervous system activity by integrating psychophysiological recording and functional neuroimaging with machine-learning based analytical methods. Results demonstrate that experientially, emotional events are well-characterized both along dimensional and categorical frameworks. Measures of central and peripheral responding discriminate among emotion categories, but are largely independent of valence and arousal. These findings suggest dimensional and categorical aspects of emotional experience are driven by separable neural substrates and demonstrate that emotional states can be objectively quantified on the basis of nervous system activity.

Live Imaging of Host-Parasite Interactions in a Zebrafish Infection Model Reveals Cryptococcal Determinants of Virulence and Central Nervous System Invasion.

UNLABELLED: The human fungal pathogen Cryptococcus neoformans is capable of infecting a broad range of hosts, from invertebrates like amoebas and nematodes to standard vertebrate models such as mice and rabbits. Here we have taken advantage of a zebrafish model to investigate host-pathogen interactions of Cryptococcus with the zebrafish innate immune system, which shares a highly conserved framework with that of mammals. Through live-imaging observations and genetic knockdown, we establish that macrophages are the primary immune cells responsible for responding to and containing acute cryptococcal infections. By interrogating survival and cryptococcal burden following infection with a panel of Cryptococcus mutants, we find that virulence factors initially identified as important in causing disease in mice are also necessary for pathogenesis in zebrafish larvae. Live imaging of the cranial blood vessels of infected larvae reveals that C. neoformans is able to penetrate the zebrafish brain following intravenous infection. By studying a C. neoformans FNX1 gene mutant, we find that blood-brain barrier invasion is dependent on a known cryptococcal invasion-promoting pathway previously identified in a murine model of central nervous system invasion. The zebrafish-C. neoformans platform provides a visually and genetically accessible vertebrate model system for cryptococcal pathogenesis with many of the advantages of small invertebrates. This model is well suited for higher-throughput screening of mutants, mechanistic dissection of cryptococcal pathogenesis in live animals, and use in the evaluation of therapeutic agents. IMPORTANCE: Cryptococcus neoformans is an important opportunistic pathogen that is estimated to be responsible for more than 600,000 deaths worldwide annually. Existing mammalian models of cryptococcal pathogenesis are costly, and the analysis of important pathogenic processes such as meningitis is laborious and remains a challenge to visualize. Conversely, although invertebrate models of cryptococcal infection allow high-throughput assays, they fail to replicate the anatomical complexity found in vertebrates and, specifically, cryptococcal stages of disease. Here we have utilized larval zebrafish as a platform that overcomes many of these limitations. We demonstrate that the pathogenesis of C. neoformans infection in zebrafish involves factors identical to those in mammalian and invertebrate infections. We then utilize the live-imaging capacity of zebrafish larvae to follow the progression of cryptococcal infection in real time and establish a relevant model of the critical central nervous system infection phase of disease in a nonmammalian model.

Central nervous system drugs: Low temperature X-ray structures of (I) the base 5-(2,3-dichlorophenyl)-2,4-diamino-6-fluoromethyl-pyrimidine (4030W92) and (II) 5-(2,6-dichlorophenyl)-1-H-2,4-diamino-6-methyl-pyrimidine methanesulphonic acid salt (227C89)

The X-ray crystal structures of (I), the base 4030W92, 5-(2,3-dichlorophenyl)-2,4-diamino-6-fluoromethyl-pyrimidine, C11H9Cl2FN4, and (II) 227C89, the methanesulphonic acid salt of 5-(2,6-dichlorophenyl)-1-H-2,4-diamino-6-methyl-pyrimidine, C11H11Cl2N4 center dot CH3O3S, have been carried out at low temperature. A detailed comparison of the two structures is given. Structure (I) is non-centrosymmetric, crystallizing in space group P2(1) with unit cell a = 10.821(3), b = 8.290(3), c = 13.819(4) angstrom, beta = 105.980(6)degrees, V = 1191.8(6) angstrom(3), Z = 4 (two molecules per asymmetric unit) and density (calculated) = 1.600 mg/m(3). Structure (II) crystallizes in the triclinic space group P (1) over bar with unit cell a = 7.686(2), b = 8.233(2), c = 12.234(2) angstrom, alpha = 78.379(4), beta = 87.195(4), gamma = 86.811(4)degrees, V = 756.6(2) angstrom(3), Z = 2, density (calculated) = 1.603 mg/m(3). Final R indices [I > 2sigma(I)] are R1 = 0.0572, wR2 = 0.1003 for (I) and R1 = 0.0558, wR2 = 0.0982 for (II). R indices (all data) are R1 = 0.0983, wR2 = 0.1116 for (I) and R1 = 0.1009, wR2 = 0.1117 for (II). 5- Phenyl-2,4 diaminopyrimidine and 6-phenyl-1,2,4 triazine derivatives, which include lamotrigine (3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine), have been investigated for some time for their effects on the central nervous system. The three dimensional structures reported here form part of a newly developed data base for the detailed investigation of members of this structural series and their biological activities.

Two functionally linked amino acids in the stem 2 region of measles virus haemagglutinin determine infectivity and virulence in the rodent central nervous system.

Rodent brain-adapted measles virus (MV) strains, such as CAM/RB and recombinant MVs based on the Edmonston strain containing the haemagglutinin (H) of CAM/RB, cause acute encephalitis after intracerebral infection of newborn rodents. We have demonstrated that rodent neurovirulence is modulated by two mutations at amino acid positions 195 and 200 in the H protein, one of these positions (200) being a potential glycosylation site. In order to analyse the effects of specific amino acids at these positions, we introduced a range of individual and combined mutations into the open reading frame of the H gene to generate a number of eukaryotic expression plasmids. The functionality of the mutant H proteins was assessed in transfected cells and by generating recombinant viruses. Interestingly, viruses caused acute encephalitis only if the amino acid Ser at position 200 was coupled with Gly at position 195, whereas viruses with single or combined mutations at these positions, including glycosylation at position 200, were attenuated. Neurovirulence was associated with virus spread and induction of neuronal apoptosis, whereas attenuated viruses failed to infect brain cells. Similar results were obtained by using primary brain-cell cultures. Our findings indicate that a structural alteration in the stem 2 region of the H protein at position 195 or 200 interferes with infectivity of rodent neurons, and suggest that the interaction of the viral attachment protein with cellular receptors on neurons is affected.

Mice lacking alpha-tocopherol transfer protein gene have severe alpha-tocopherol deficiency in multiple regions of the central nervous system

Ataxia with vitamin E deficiency is caused by mutations in a-tocopherol transfer protein (a-TTP) gene and it can be experimentally generated in mice by a-TTP gene inactivation (a-TTP-KO). This study compared a-tocopherol (a-T) concentrations of five brain regions and of four peripheral organs from 5 months old, male and female, wild-type (WT) and a-TTP-KO mice. All brain regions of female WT mice contained significantly higher a-T than those from WT males. a-T concentration in the cerebellum was significantly lower than that in other brain regions of WT mice. These sex and regional differences in brain a-T concentrations do not appear to be determined by a-TTP expression which was undetectable in all brain regions. All the brain regions of a-TTP-KO mice were severely depleted in a-T. The concentration of another endogenous antioxidant, total glutathione, was unaffected by gender but was decreased slightly but significantly in most brain regions of a-TTP-KO mice. The results show that both gender and the hepatic a-TTP, but not brain a-TTP gene expression are important in determining a-T concentrations within the brain. Interestingly, functional abnormality (ataxia) develops only very late in a-TTP-KO mice in spite of the severe a-tocopherol deficiency in the brain starting at an early age.

Organisation of the nervous system in the Acoela: an immunocytochemical study

In order to broaden the information about the organisation of the nervous system in taxon Acoela, an immunocytochemical study of an undetermined Acoela from Cape Kartesh, Faerlea glomerata, Avagina incola and Paraphanostoma crassum has been performed. Antibodies to 5-HT and the native flatworm neuropeptide GYIRFamide were used. As in earlier studies, the pattern of 5-HT immunoreactivity revealed an anterior structure composed mainly of commissures, a so-called commissural brain. Three types of brain shapes were observed. No regular orthogon was visualised. GYIRFamide immunoreactive cell clusters were observed peripherally to the 5-HT immunoreactive commissural brain. Staining with anti-GYIRFamide revealed more nerve processes than did staining with anti-FMRFamide. As no synapomorphies were found in the organisation of the nervous system of the Acoela and that of the Platyhelminthes, the results support the view that the Acoela is not a member of the Platyhelminthes. (C) 2001 Harcourt Publishers Ltd.

Basiepidermal nervous system in Nemertoderma westbladi (Nemertodermatida): GYIRFamide immunoreactivity

The Nemertodermatida are a small group of microscopic marine worms. Recent molecular studies have demonstrated that they are likely to be the earliest extant bilaterian animals. What was the nervous system (NS) of a bilaterian ancestor like? In order to answer that question, the NS of Nemertoderma westbladi was investigated by means of indirect immunofluorescence technique and confocal scanning laser microscopy. The antibodies to a flatworm neuropeptide GYIRFamide were used in combination with anti-serotonin antibodies and phalloidin-TRITC staining. The immunostaining revealed an entirely basiepidermal NS. A ring lying outside the body wall musculature at the level of the statocyst forms the only centralisation, the