Lipid Binding Defects and Perturbed Synaptogenic Activity of a Collybistin R290H Mutant That Causes Epilepsy and Intellectual Disability

Signaling at nerve cell synapses is a key determinant of proper brain function, and synaptic defects—or synaptopathies—are at the basis of many neurological and psychiatric disorders. In key areas of the mammalian brain, such as the hippocampus or the basolateral amygdala, the clustering of the scaffolding protein Gephyrin and of γ-aminobutyric acid type A receptors at inhibitory neuronal synapses is critically dependent upon the brain-specific guanine nucleotide exchange factor Collybistin (Cb). Accordingly, it was discovered recently that an R290H missense mutation in the diffuse B-cell lymphoma homology domain of Cb, which carries the guanine nucleotide exchange factor activity, leads to epilepsy and intellectual disability in human patients. In the present study, we determined the mechanism by which the Cb^R290H mutation perturbs inhibitory synapse formation and causes brain dysfunction. Based on a combination of biochemical, cell biological, and molecular dynamics simulation approaches, we demonstrate that the R290H mutation alters the strength of intramolecular interactions between the diffuse B-cell lymphoma homology domain and the pleckstrin homology domain of Cb. This defect reduces the phosphatidylinositol 3-phosphate binding affinity of Cb, which limits its normal synaptogenic activity. Our data indicate that impairment of the membrane lipid binding activity of Cb and a consequent defect in inhibitory synapse maturation represent a likely molecular pathomechanism of epilepsy and mental retardation in humans.     

Integrative taxonomy reveals a new species of Callisto (Lepidoptera,Gracillariidae) in the Alps

Europe has one of the best-known Lepidopteran faunas in the world, yet many species are still being discovered, especially in groups of small moths. Here we describe a new gracillariid species from the south-eastern Alps, Callisto basistrigella Huemer, Deutsch & Triberti, sp. n. It shows differences from its sister species Callisto coffeella in morphology, the barcode region of the cytochrome c oxidase I gene and the nuclear gene histone H3. Both Callisto basistrigella and Callisto coffeella can co-occur in sympatry without evidence of admixture. Two Callisto basistrigella specimens show evidence of introgression. We highlight the importance of an integrative approach to delimit species, combining morphological and ecological data with mitochondrial and nuclear sequence data. Furthermore, in connection with this study, Ornix blandella Müller-Rutz, 1920, syn. n. is synonymized with Callisto coffeella (Zetterstedt, 1839).     

On the False Discovery Rate and Expected Type I Errors

The paper is concerned with expected type I errors of some stepwise multiple test procedures based on independent p‐values controlling the so‐called false discovery rate (FDR). We derive an asymptotic result for the supremum of the expected type I error rate(EER) when the number of hypotheses tends to infinity. Among others, it will be shown that when the original Benjamini‐Hochberg step‐up procedure controls the FDR at level α, its EER may approach a value being slightly larger than α/4 when the number of hypotheses increases. Moreover, we derive some least favourable parameter configuration results, some bounds for the FDR and the EER as well as easily computable formulae for the familywise error rate (FWER) of two FDR‐controlling procedures. Finally, we discuss some undesirable properties of the FDR concept, especially the problem of cheating.     

A heme-nonapeptide tracer for electron microscopy

Summary A heme-nonapeptide (H-9-P)¹, applicable to electron microscopic cytochemistry via peroxidase-like activity, was prepared by passing horse heart cytochrome c through a column with Sepharose and covalently attached trypsin. After purification by column chromatography (Sephadex G50 Superfine, Biogel P-2) a maximal yield of 50% and purity of >99% was achieved. A concise schedule allows for inexpensive preparation of H-9-P with standard laboratory equipment. H-9-P has the following properties: Its structure is (14) Cys-Ala-Gln-Cys-His-Thr-Val-Glu-Lys (22) with heme attached to Cys (14) and (17). MW=1630, pI=4.95, _E(max) ^{pH 7} = 397.5 nm, _{22 °C, pH 7} ^{397.5 nm} = 1.11 × 10⁵ [Liter/Mole x cm]. With the use of a diaminobenzidine-H₂O₂-medium — as applied for cytochemistry — we determined spectrophotometrically a pH_opt=12.5 and an apparent K₅ = 3.14 × 10^{– 3} [M]. Glutardialdehyde leads to considerable de-activation and, according to SDS-polyacrylamide-gel-electrophoresis, to diffuse crosslinking accompanied by a shift of the active pH-region towards neutral pH values. An attempt was made to optimize the cytochemical assay. The peroxidase-like activity of H-9-P is well comparable to that of other heme-tracers; only horseradish peroxidase has a higher turnover number. When injected to mice or added to cell suspensions, even high concentrations of H-9-P did not entail any signs of toxicity.Abbreviations AAA amino acid analysis - AHC ammoniumhydrogencarbonate - BSA bovine serum albumin - Cyt c cytochrome c - DAB 5,3-diaminobenzidine - GA glutardialdehyde - H-8-P heme-octapeptide - H-9-P heme-nonapeptide - H-11-P heme-undecapeptide - HR-POX horseradish peroxidase - MW molecular weight - PAGE polyacrylamid-gel-electrophoresis - pI isoelectric point - SDS sodiumdodecylsulphate - SG-TLC silicagel-thin-layer-chromatography This work was supported by the Österreichische Forschungsfonds     

Natural climate solutions versus bioenergy: Can carbon benefits of natural succession compete with bioenergy from short rotation coppice?

Short rotation plantations are often considered as holding vast potentials for future global bioenergy supply. In contrast to raising biomass harvests in forests, purpose‐grown biomass does not interfere with forest carbon (C) stocks. Provided that agricultural land can be diverted from food and feed production without impairing food security, energy plantations on current agricultural land appear as a beneficial option in terms of renewable, climate‐friendly energy supply. However, instead of supporting energy plantations, land could also be devoted to natural succession. It then acts as a long‐term C sink which also results in C benefits. We here compare the sink strength of natural succession on arable land with the C saving effects of bioenergy from plantations. Using geographically explicit data on global cropland distribution among climate and ecological zones, regionally specific C accumulation rates are calculated with IPCC default methods and values. C savings from bioenergy are given for a range of displacement factors (DFs), acknowledging the varying efficiency of bioenergy routes and technologies in fossil fuel displacement. A uniform spatial pattern is assumed for succession and bioenergy plantations, and the considered timeframes range from 20 to 100 years. For many parameter settings—in particular, longer timeframes and high DFs—bioenergy yields higher cumulative C savings than natural succession. Still, if woody biomass displaces liquid transport fuels or natural gas‐based electricity generation, natural succession is competitive or even superior for timeframes of 20–50 years. This finding has strong implications with climate and environmental policies: Freeing land for natural succession is a worthwhile low‐cost natural climate solution that has many co‐benefits for biodiversity and other ecosystem services. A considerable risk, however, is C stock losses (i.e., emissions) due to disturbances or land conversion at a later time.     

Importance of mixotrophic bacterivory can be predicted by light and loss rates

Recent observational studies form oligotrophic waters provide ample evidence that mixotrophic flagellates often account for the bulk of bacterivory. However, we lack a general framework that allows a mechanistic understanding of success of mixotrophs in the competition with heterotrophic bacterivores. This is especially needed for integrating mixotrophy in models of the microbial loop. Based on general tradeoffs linked to the combined resource use in mixotrophs (generalist versus specialist), we propose a concept where mixotrophs are favored by conditions of high light – low losses, corresponding to the situation found in the surface waters of oligotrophic oceans. Under such conditions, they can achieve positive net growth at very low resource levels, allowing simultaneous competition with specialized protists. Conversely, heterotrophic bacterivores and photoautotrophs should be especially favored in more productive and low‐light conditions. We show experimentally that the combined effect of light and loss rates (dilution) predicts the success of mixotrophic bacterivorous flagellates. Moreover, our results suggest that total bacterivory, contrary as seen in the traditional microbial loop concept, has a more intricate coupling to light.     

Bukettförmige Strukturen im Ependym der Regio hypothalamica des III. Ventrikels beim Kaninchen

Zusammenfassung Die Wand des III. Ventrikels (Regio hypothalamica) vom erwachsenen Kaninchen wurde elektronenmikroskopisch untersucht. — Unterschiedliche keulenförmige portsätze, deren Perikaryen in nahen und entfernten Regionen liegen, dringen in den Ventrikel ein. Sie heben eine Ependymzelle ab und bilden eine bukettförmige Struktur. Einige Fortsätze enthalten eine spärliche feingranulierte Masse, andere Bläschen (600–1500 Å) oder Bläschen mit dichtem Kern (450–1200 Å). Inmitten des Buketts kann eine Nervenzelle liegen, die einen dicken Fortsatz gegen das Hypendym schickt. Unterhalb des Buketts findet man eine andere Nervenzelle, die Fortsätze ins Bukett sendet. Zahlreiche in das Bukett eintretende Fortsätze stammen aus entfernteren Kerngebieten. Die funktionelle Bedeutung der Strukturen (Neurosekretion ? Resorption ? Rezeptor ?) wird diskutiert.

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Bouquet-like ependymal structures in the hypothalamic region of the 3rd Ventricle (rabbit)The question of neurosecretion or receptor function

Summary The wall of the III. ventricle (Regio hypothalamica) of the adult rabbit has been investigated electron microscopically. —Various bulblike processes of nerve cells, having their perikarya in close or distant regions, penetrate into the ventricle. They lift an ependymal cell and form a bouquet-like structure. Some of the processes contain a sparse granulated material and others include vesicles (600–1500 Å) or dense-cored vesicles (450–1200 Å). In the middle of the bouquet a perikaryon may be seen extending a thick process towards the hypendyma. Below the bouquet another perikaryon may be found extending several processes into the bouquet. The functional significance of these structures (neurosecretion ? resorption? receptor?) is discussed.

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Die Untersuchung wurde mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft durchgeführt.