Posttranscriptional Gene Regulation by Spatial Rearrangement of the 3′ Untranslated Region

Translation termination at premature termination codons (PTCs) triggers degradation of the aberrant mRNA, but the mechanism by which a termination event is defined as premature is still unclear. Here we show that the physical distance between the termination codon and the poly(A)-binding protein PABPC1 is a crucial determinant for PTC recognition in human cells. “Normal” termination codons can trigger nonsense-mediated mRNA decay (NMD) when this distance is extended; and vice versa, NMD can be suppressed by folding the poly(A) tail into proximity of a PTC or by tethering of PABPC1 nearby a PTC, indicating an evolutionarily conserved function of PABPC1 in promoting correct translation termination and antagonizing activation of NMD. Most importantly, our results demonstrate that spatial rearrangements of the 3′ untranslated region can modulate the NMD pathway and thereby provide a novel mechanism for posttranscriptional gene regulation

A Modified RMCE-Compatible Rosa26 Locus for the Expression of Transgenes from Exogenous Promoters

Generation of gain-of-function transgenic mice by targeting the Rosa26 locus has been established as an alternative to classical transgenic mice produced by pronuclear microinjection. However, targeting transgenes to the endogenous Rosa26 promoter results in moderate ubiquitous expression and is not suitable for high expression levels. Therefore, we now generated a modified Rosa26 (modRosa26) locus that combines efficient targeted transgenesis using recombinase-mediated cassette exchange (RMCE) by Flipase (Flp-RMCE) or Cre recombinase (Cre-RMCE) with transgene expression from exogenous promoters. We silenced the endogenous Rosa26 promoter and characterized several ubiquitous (pCAG, EF1α and CMV) and tissue-specific (VeCad, αSMA) promoters in the modRosa26 locus in vivo. We demonstrate that the ubiquitous pCAG promoter in the modRosa26 locus now offers high transgene expression. While tissue-specific promoters were all active in their cognate tissues they additionally led to rare ectopic expression. To achieve high expression levels in a tissue-specific manner, we therefore combined Flp-RMCE for rapid ES cell targeting, the pCAG promoter for high transgene levels and Cre/LoxP conditional transgene activation using well-characterized Cre lines. Using this approach we generated a Cre/LoxP-inducible reporter mouse line with high EGFP expression levels that enables cell tracing in live cells. A second reporter line expressing luciferase permits efficient monitoring of Cre activity in live animals. Thus, targeting the modRosa26 locus by RMCE minimizes the effort required to target ES cells and generates a tool for the use exogenous promoters in combination with single-copy transgenes for predictable expression in mice

The RSPO–LGR4/5–ZNRF3/RNF43 module controls liver zonation and size

LGR4/5 receptors and their cognate RSPO ligands potentiate Wnt/β-catenin signalling and promote proliferation and tissue homeostasis in epithelial stem cell compartments. In the liver, metabolic zonation requires a Wnt/β-catenin signalling gradient, but the instructive mechanism controlling its spatiotemporal regulation is not known. We have now identified the RSPO-LGR4/5-ZNRF3/RNF43 module as a master regulator of Wnt/β-catenin-mediated metabolic liver zonation. Liver-specific LGR4/5 loss of function (LOF) or RSPO blockade disrupted hepatic Wnt/β-catenin signalling and zonation. Conversely, pathway activation in ZNRF3/RNF43 LOF mice or with recombinant RSPO1 protein expanded the hepatic Wnt/β-catenin signalling gradient in a reversible and LGR4/5-dependent manner. Recombinant RSPO1 protein increased liver size and improved liver regeneration, whereas LGR4/5 LOF caused the opposite effects, resulting in hypoplastic livers. Furthermore, we show that LGR4(+) hepatocytes throughout the lobule contribute to liver homeostasis without zonal dominance. Taken together, our results indicate that the RSPO-LGR4/5-ZNRF3/RNF43 module controls metabolic liver zonation and is a hepatic growth/size rheostat during development, homeostasis and regeneration

Global patterns and drivers of ecosystem functioning in rivers and riparian zones

AbstractRiver ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.Abstract River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale

Global patterns and drivers of ecosystem functioning in rivers and riparian zones

Os ecossistemas fluviais recebem e processam grandes quantidades de carbono orgânico terrestre, cujo destino depende fortemente da atividade microbiana. A variação e o controle das taxas de processamento, no entanto, são mal caracterizados à escala global. Em resposta, utilizamos uma rede de pesquisa de pares e um ensaio de processamento de carbono altamente padronizado para conduzir um experimento de campo em escala global em mais de 1.000 locais fluviais e ribeirinhos. Descobrimos que os biomas da Terra têm assinaturas distintas de processamento de carbono. O processamento lento é evidente em todas as latitudes, enquanto as taxas rápidas são restritas às latitudes mais baixas. Tanto a taxa média como a variabilidade diminuem com a latitude, sugerindo restrições de temperatura em direção aos pólos e papéis maiores para outros fatores ambientais (por exemplo, carga de nutrientes) em direção ao equador. Estes resultados e dados preparam o terreno para uma “biomonitorização de próxima geração” sem precedentes, estabelecendo linhas de base para ajudar a quantificar os impactos ambientais no funcionamento dos ecossistemas à escala global.River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale

High Voltage Electrochemical Double Layer Capacitors Containing Adiponitrile-Based Electrolytes

Abstract not Available.</jats:p

Towards a better understanding of carotenoid metabolism in animals

AbstractVitamin A derivatives (retinoids) are essential components in vision; they contribute to pattern formation during development and exert multiple effects on cell differentiation with important clinical implications. All naturally occurring vitamin A derives by enzymatic oxidative cleavage from carotenoids with provitamin A activity. To become biologically active, these plant-derived compounds must first be absorbed, then delivered to the site of action in the body, and metabolically converted to the real vitamin. Recently, molecular players of this pathway were identified by the analysis of blind Drosophila mutants. Similar genome sequences were found in vertebrates. Subsequently, these homologous genes were cloned and their gene products were functionally characterized. This review will summarize the advanced state of knowledge about the vitamin A biosynthetic pathway and will discuss biochemical, physiological, developmental and medical aspects of carotenoids and their numerous derivatives

RBP4 Disrupts Vitamin A Uptake Homeostasis in a STRA6-Deficient Animal Model for Matthew-Wood Syndrome

SummaryThe cellular uptake of vitamin A from its RBP4-bound circulating form (holo-RBP4) is a homeostatic process that evidently depends on the multidomain membrane protein STRA6. In humans, mutations in STRA6 are associated with Matthew-Wood syndrome, manifested by multisystem developmental malformations. Here we addressed the metabolic basis of this inherited disease. STRA6-dependent transfer of retinol from RBP4 into cultured NIH 3T3 fibroblasts was enhanced by lecithin:retinol acyltransferase (LRAT). The retinol transfer was bidirectional, strongly suggesting that STRA6 acts as a retinol channel/transporter. Loss-of-function analysis in zebrafish embryos revealed that Stra6 deficiency caused vitamin A deprivation of the developing eyes. We provide evidence that, in the absence of Stra6, holo-Rbp4 provokes nonspecific vitamin A excess in several embryonic tissues, impairing retinoic acid receptor signaling and gene regulation. These fatal consequences of Stra6 deficiency, including craniofacial and cardiac defects and microphthalmia, were largely alleviated by reducing embryonic Rbp4 levels by morpholino oligonucleotide or pharmacological treatments

Combined deletion of Lgr4 and Lgr5 impairs embryonic mouse development

Lgr4 and Lgr5 proteins are known markers of adult and embryonic tissue stem cells in various organs. However, the role of these proteins in propagating and maintaining individual tissue stem cell compartments is still controversial. While it was reported that Lgr4 is dispensable for normal embryonic gut development, Lgr4 deletion functionally impaired maintenance of the postnatal and adult intestinal crypt stem cell compartment. Furthermore, concomitant deletion of Lgr4 in Lgr5-null embryos was able to rescue their perinatal lethality, whereas combined deletion of Lgr4 and Lgr5 in adult mice exacerbated the latter phenotype, suggesting antagonistic or complementary functions of both receptors, respectively. While the effects of Lgr4 deletion during embryonic skin and kidney development have been reported, combined deletion of Lgr4 and Lgr5 has not been studied to date. To elucidate the functions of Lgr4 and Lgr5 during intestinal crypt development and to study their role in developing kidney and skin, we generated homozygous mice lacking either Lgr4 (Lgr4KO), Lgr5 (Lgr5KO) or both receptors (Lgr4/5dKO). Lgr4 deletion resulted in loss of Lgr5+ intestinal stem cells and impaired proliferation in the developing gut of E16.5 mice, a phenotype that was not further increased nor ameliorated by combined deletion of Lgr4 and Lgr5 (Lgr4/5dKO). In skin, E16.5 Lgr4KO and Lgr4/5dKO mice displayed impaired proliferation of basal cell progenitors accompanied by reduced epidermal thickness and reduced numbers of hair follicles. In contrast to E16.5 Lgr4KO mice, Lgr4/5dkO mice did neither show dilated kidney tubules nor cysts. However, E16.5 Lgr4/5dKO mice showed impaired kidney cell proliferation which was not observed in Lgr4KO mice. In summary, our data show that combined deletion of Lgr4 and Lgr5 impairs embryonic development with a dominant role of Lgr4 and support a complementary rather than an antagonistic function for both receptors