Regulation of Embryonic Cell Adhesion by the Prion Protein

Prion proteins (PrPs) are key players in fatal neurodegenerative disorders, yet their physiological functions remain unclear, as PrP knockout mice develop rather normally. We report a strong PrP loss-of-function phenotype in zebrafish embryos, characterized by the loss of embryonic cell adhesion and arrested gastrulation. Zebrafish and mouse PrP mRNAs can partially rescue this knockdown phenotype, indicating conserved PrP functions. Using zebrafish, mouse, and Drosophila cells, we show that PrP: (1) mediates Ca+2-independent homophilic cell adhesion and signaling; and (2) modulates Ca+2-dependent cell adhesion by regulating the delivery of E-cadherin to the plasma membrane. In vivo time-lapse analyses reveal that the arrested gastrulation in PrP knockdown embryos is due to deficient morphogenetic cell movements, which rely on E-cadherin–based adhesion. Cell-transplantation experiments indicate that the regulation of embryonic cell adhesion by PrP is cell-autonomous. Moreover, we find that the local accumulation of PrP at cell contact sites is concomitant with the activation of Src-related kinases, the recruitment of reggie/flotillin microdomains, and the reorganization of the actin cytoskeleton, consistent with a role of PrP in the modulation of cell adhesion via signaling. Altogether, our data uncover evolutionarily conserved roles of PrP in cell communication, which ultimately impinge on the stability of adherens cell junctions during embryonic development

mTORC2 controls neuron size and Purkinje cell morphology independent of mTORC1

Prenatal brain development is mainly accomplished by extensive proliferation of neuronal precursor cells whereas postnatal brain growth in mammals is mainly mediated by the growth of those post-mitotic nerve cells. The neuron size and the branching pattern of the dendritic tree are highly controlled during development to enable the proper connectivity of neuronal circuits and the accurate electrical transmission in the adult which is a prerequisite for the brain to function normally. Aberrations in size, morphology or connectivity have been shown to be the cause for various brain disorders. Neuron size and dendrite development are controlled by intrinsic mechanisms, trophic factors and neuronal activity, processes that need the concerted action of a plethora of signaling molecules. A central integrator of various signaling cascades is the mammalian target of rapamycin (mTOR) and as such it contributes to brain development and function and is thus also implicated in the pathophysiology of psychiatric disorders. mTOR is a serine threonine protein kinase that is highly conserved from yeast to humans and has been found to be part of at least two multi-protein complexes mTORC1 and mTORC2. The formation of mTORC1 is dependent on the protein raptor whereas mTORC2 assembly relies on the protein rictor. In recent years a complex picture about the function of mTORC1 has emerged by use of rapamycin, an immunosuppressive drug that acutely inhibits mTORC1 formation and activity and has attributed mTORC1 a major role in the regulation of cell size and proliferation. However, because the activity of mTORC2 is only depleted upon long term application of rapamycin, research advancement on its function was thus far impeded. Due to the early embryonic lethality of raptor or rictor knockout in mammals conditional knockout models were constructed. Whereas tissue specific knockout of raptor led to characteristic alterations, knockout of rictor in several organs such as skeletal muscle and adipose tissue provided none or only a weak phenotype. Several cell culture studies assigned mTORC2 a role in cytoskeletal modifications but in vivo confirmation is still lacking. The current knowledge about mTORC2 is restricted to the downstream targets Akt/PKB (proteinkinase B) and PKC (protein kinase C) which belong to the AGC kinase family. Those kinases are reported to influence cell morphology, growth and survival and are also essential regulators of brain development and function. PKCs are involved in synaptic plasticity and neurotransmitter release and, hence, also in the pathophysiological mechanisms of psychiatric disorders especially in schizophrenia and bipolar disorder. Concordantly, several psychiatric agents have been shown to alter PKC signaling. This emphasizes the urge to analyze the role of mTORC2 in the central nervous system. In this dissertation the role of mTORC2 was analyzed in the central nervous system and in specific sub-populations of neurons by deletion of rictor. I discovered, that in contrast to all other organs analyzed so far, rictor knockout in the brain reveals a pronounced phenotype. The brain-size of those mice shows an enormous reduction to almost half of that of control mice which is caused mainly by the reduction of neuron size. The reduced cell size is observed in neurons derived from different brain areas in vitro and in vivo but is most prominent in Purkinje cells of the cerebellum, the cell type with highest rictor expression. In addition, dendrite morphology is majorly disrupted and the formation of dendritic spines is affected which correlates with a decreased neuronal activity. The Purkinje cell phenotype can also be reproduced in a Purkinje cell specific knockout of rictor and thus demonstrates that the effect of rictor deletion in neurons is cell autonomous. Moreover, Purkinje cell axonal path-finding is affected which correlates with the decrease in phosphorylation of the neuron specific PKC target protein GAP-43, a known regulator for axon growth and path-finding. Molecular analysis reveals that rictor is essential for the activity of all conventional PKC isoforms and the novel PKCε in vivo and in vitro in neurons which influences the function of downstream targets important for cytoskeleton modifications such as GAP-43, MARCKs and neurofascin. In addition, rictor controls the phosphorylation of Akt but does not alter mTORC1 signaling towards its downstream effectors. In summary it becomes clear that rictor is important in the development and maturation of neurons and controls their size and neuron structure which influences the entire brain function and affects the behavior of the mice. Thus, these data encompass a new role of rictor in CNS disorders

Inactivation of mTORC1 in the Developing Brain Causes Microcephaly and Affects Gliogenesis

The mammalian target of rapamycin (mTOR) regulates cell growth in response to various intracellular and extracellular signals. It assembles into two multiprotein complexes: the rapamycin-sensitive mTOR complex 1 (mTORC1) and the rapamycin-insensitive mTORC2. In this study, we inactivated mTORC1 in mice by deleting the gene encoding raptor in the progenitors of the developing CNS. Mice are born but never feed and die within a few hours. The brains deficient for raptor show a microcephaly starting at E17.5 that is the consequence of a reduced cell number and cell size. Changes in cell cycle length during late cortical development and increased cell death both contribute to the reduction in cell number. Neurospheres derived from raptor-deficient brains are smaller, and differentiation of neural progenitors into glia but not into neurons is inhibited. The differentiation defect is paralleled by decreased Stat3 signaling, which is a target of mTORC1 and has been implicated in gliogenesis. Together, our results show that postnatal survival, overall brain growth, and specific aspects of brain development critically depend on mTORC1 function

Energetische Nutzung von Abfällen in Müll-Heizkraftwerken und Abschätzung der klimarelevanten Emissionen

Im Rahmen des Projekts "Instrumente für Klimagas-Reduktions-Strategien"(lKARUS) sollen im Teilprojekt 4, Bereich 7, die Emissionen sogenannter "klimarelevanter" Abgase aus der energetischen Nutzung von Abfällen in Müll-Heizkraftwerken bzw. Hausmüll-Verbrennungsanlagen in Deutschland bilanziert werden. Als klimarelevante Gase kommen hierbei - Kohlendioxid - Kohlenmonoxid - Stickoxide - Schwefeloxide - Chlorwasserstoff - Fluorwasserstoff - organische Kohlenwasserstoffe bzw. -derivate näher in Betracht. Daneben sollen Stäube als klimarelevante Emissionen Berücksichtigung finden. Bezugsjahr für die Bilanzierungen soll das Jahr 1989 sein. Mit Blick auf die Klimarelevanz der CO$_{2}$-Emissionen ist bei der Abfallverbrennung zwischen sogenanntem "Kreislauf-CO$_{2}$" welches z.B. aus der Verbrennung von Holz, Papier oder vegetabilen Abfällen ensteht und dem sogenannten "klimarelevanten CO$_{2}$ '', das aus der Verbrennung von zu Abfall gewordenen Produkten auf der Basis von fossilen Ausgangsstoffen entsteht, zu unterscheiden. Aufbauend auf den Ergebnissen o.g. Untersuchungen soll die Erstellung von Prognosen über die im Jahr 2005 zu erwartenden Emissionen klimarelevanter Gase aus der thermischen Verwertung von Abfällen erfolgen. [...

Influence of chloride concentration on the formation of AOX in UV oxidative system

In this study, the effects of chloride ion concentration and pH on UV oxidation treatment were examined. Acetone and sodium dodecyl sulfate (ABS) were used as organic substances. The treatment efficiencies of these chemicals by UV/H2O2 oxidation using a laboratory scale UV-free surface reactor (UV-FSR) with or without Cl- addition at different pH values was compared. Results of this study indicated that Cl- concentration and the chemical structure of the substances are more decisive than pH in the oxidation process. There was no AOX at the start of the experiments but as a result of oxidation a de novo synthesis of AOX was observed, and these AOX(de novo) compounds were destroyed during the treatment. Treatment was followed by TOC and AOX measurements. Approximately 98% and 95% TOC removal efficiencies were obtained for the treatment of acetone and ABS containing wastewaters, respectively. (C) 2006 Elsevier B.V. All rights reserved

Effect of chloride concentration on the oxidation of EDTA in UV-FSR oxidative system

This study focused on the effect of chloride concentration and pH on the photochemical degradation of ethylenediaminetetraacetic acid-disodium salt (C10H14N2Na2O8 center dot 2H(2)O, EDTA) under advanced oxidation using UV/H2O2 system. The treatment of this chemical by UV/H2O2 oxidation using a laboratory scale UV-free surface reactor (UV-FSR) with (1000 and 10,000 mg/l Cl-) and without Cl- addition at different pH values (pH 3, 7 and 10) was compared. Results of this study indicated that Cl- concentration is more decisive than pH in the oxidation process. There was no AOX at the start of the experiments but as a result of oxidation a de novo synthesis of AOX was observed, and these AOX(de novo) compounds were destroyed during the treatment. Treatment was followed by TOC and AOX measurements. Approximately 95% TOC removal efficiency was obtained for the treatment of EDTA-containing synthetic water. Owing to kinetic studies, it was found that the TOC degradation in all experiments fitted to the first order reaction law. (C) 2007 Elsevier B.V. All rights reserved

AOX formation and elimination in the oxidative treatment of synthetic wastewaters in a UV-free surface reactor

Intention, Goal, Scope, Background. The effect of chloride concentration and pH on the UV oxidation systems was examined. Phenol and methanol were used as organic substances. The treatment of these chemicals by UV oxidation using a newly developed lab scale pretest UV-Free Surface Reactor (UV-FSR) with and without Cl- addition at different PH values, is evaluated. Results of this study indicated that the Cl- concentration of the water and the chemical structure of the substances is more important than the pH of the water. There was no AOX at the beginning of the experiments, but a de-novo synthesis of AOX was observed during the batch experiments. This is caused by the high chloride content of the wastewaters. It can be supposed that OH-radicals oxidize some chloride-ions to form chlorine, which further reacts with organic compounds. During the treatment, these AOX compounds which are produced from the beginning of the reaction are destroyed again. Evaluations of these experiments were done according to TOC and AOX results. Approximately 80% and 99% TOC removal efficiencies were obtained for the treatment of Phenol and Methanol-containing wastewaters, respectively

Energetische Nutzung von Abfaellen in Muell-Heizkraftwerken und Abschaetzung der klimarelevanten Emissionen

Bei der Bearbeitung vorliegender Aufgabenstellung wurde wie folgt vorgegangen: - Anhand einer Bilanz ueber die Entsorgung von Abfaellen im Bundesgebiet werden die Abfaelle, die zur Entsorgung in Hausmuell-Verbrennungsanlagen gelangen, quantifiziert und zu den sonstigen Abfaellen, die im Bundesgebiet entsorgt werden, in Relation gesetzt. -Charakterisierung und Quantifizierung der Abfaelle, die im Jahr 1989 in Hausmuell-Verbrennungsanlagen entsorgt wurden. - Bestimmung des Kohlenstoffgehalts in Abfaellen, die in Hausmuell-Verbrennungsanlagen entsorgt werden. Hierbei wird der Anteil des Kohlenstoffs, der bei seiner Verbrennung zu klimarelevantem CO_2 fuehrt, beruecksichtigt. - Quantifizierung der Mengen an Chlor, Fluor, Schwefel und Stickstoff in Abfaellen, die bei der Verbrennung in Hausmuell-Verbrennungsanlagen klimarelevante Emissionen verursachen. -Charakterisierung der Hausmuell-Verbrennungsanlagen hinsichtlich der Verfahrenstechnik der Abfallverbrennung und Abgasreinigung. - Erstellung von Stoff- bzw. Massenbilanzen fuer die Entsorgung von Abfaellen in Hausmuell-Verbrennungsanlagen. - Erstellung einer Energiebilanz zur Energienutzung bzw. Energieabgabe in Hausmuell-Verbrennungsanlagen fuer das Bezugsjahr 1989. - Abschaetzung von Investitions- und Betriebskosten von Hausmuell-Verbrennungsanlagen. - Orientierende Abschaetzung der Substitution von fossilen Brennstoffen durch die Nutzung von elektrischer und thermischer Energie aus Hausmuell-Verbrennungsanlagen aus energetischer Sicht und mit Blick auf klimarelevante Emissionen. - Erstellung von Prognosen fuer das Jahr 2005 ueber Emissionen an klimarelevanten Gasen aus Hausmuell-Verbrennungsanlagen. (orig./SR)The task at hand was negotiated as follows: A balance of waste disposal in the German Federal Republic was elaborated in order to quantify wastes disposed of via household waste combustion plants and set this in relation to other waste flows in the country. Further: characterisation and quantification of wastes disposed of via household waste combustion plants in 1989; determination of the carbon content of wastes disposed of via household waste combustion plants with due consideration to the carbon fraction released as greeenhouse gas CO_2; quantification of chlorine, fluorine, sulphur and nitrogen in wastes to the extent they give rise to climatically relevant emissions from household waste combustion plants characterisation of household waste combustion plants with regard to their process techniques of waste combustion and exhaust gas purification; compilation of materials and mass balances of waste disposal via household waste combustion plants; compilation of an energy balance of energy utilisation and generation in household waste combustion plants in 1989; estimation of investment and operating costs of household waste combustion plants; orienting estimation of the replacement of fossil fuels by electric and thermal energy from household waste combustion plants with regard to both energy economy and greenhouse gas emissions; and eleboration of a forecost for the year 2005 on greenhouse gas emissions from household waste combustion plants. (orig./SR)Available from TIB Hannover: RO 9946(4-10) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman