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Albert-Ludwigs-Universität Freiburg Fakultät für Biologie

Overview
Works: 159 works in 159 publications in 2 languages and 802 library holdings
Roles: Degree grantor, Contributor, isb, Other, his
Publication Timeline
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Most widely held works by Albert-Ludwigs-Universität Freiburg
MxA represents a decisive species barrier against influenza viruses in vivo by Ebrahim Hassan( )

1 edition published in 2018 in English and held by 17 WorldCat member libraries worldwide

Abstract: In vivo evasion of MxA reveals pandemic potential of emerging influenza A viruses<br><br>Christoph M. Deeg1,$, Ebrahim Hassan1,2,3,$, Pascal Mutz1,$, Lara Rheinemann1, Veronika Götz1, Linda Magar1, Mirjam Schilling1, Carsten Kallfass1, Cindy Nürnberger1,2, Sébastien Soubies1, Georg Kochs1, Otto Haller1, Martin Schwemmle1, and Peter Staeheli1<br><br>1 Institute of Virology, Medical Center University of Freiburg, Freiburg, Germany<br>2 Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg <br>3 Microbiology Department, Faculty of Science, Ain Shams University, Cairo, Egypt <br>$ These authors contributed equally to this work<br><br>Influenza A viruses pose a constant threat to humans, because zoonotic viral transmissions can cause severe disease and give rise to devastating pandemics. Currently, it is not possible to predict the pandemic potential of avian influenza A viruses. We now describe a new mouse model suitable for risk assessment. It is based on the finding that innate restriction factors represent effective species barriers that need to be overcome by viruses trying to invade a human host. In mice, innate immune control of influenza viruses is mediated by the interferon-regulated Mx1 gene. The MX1 orthologue of humans (encoding MxA protein) provides broad resistance to influenza and other viruses in cell culture systems. MxA is targeting the nucleoprotein of influenza A viruses which encapsidates the viral genome and is pivotal to virus replication. Influenza A viruses that successfully established stable lineages in humans acquired adaptive mutations in the nucleoprotein that allow partial MxA escape in cell culture experiments. Our new mouse strain lacks functional endogenous Mx genes but instead carries the human MX1 locus as transgene. Our transgenic mice were largely resistant to highly pathogenic avian H5 and H7 influenza A viruses, but were almost as susceptible to infection with influenza viruses of human origin as non-transgenic littermates. We further demonstrate that an engineered avian H7N7 influenza virus carrying a nucleoprotein with signature mutations typically found in human virus isolates was more virulent in transgenic mice than the parental virus. These findings illustrate that a few amino acid changes in the viral nucleoprotein can mediate escape from MxA restriction in vivo. They further suggest that equivalent mutations need to be acquired by any emerging influenza A viruses before they can spread efficiently in the human population
Genetically engineered antigen-specific treg cells in immunotherapy: opportunities and challenges by Karolina Ebert( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Abstract: The success of a transplantation is restricted by the immune response of the recipient directed against the donor's graft (graft rejection) or the other way around; immune response of the donor against the recipient (GvHD). Promoting a state of immunological tolerance instead of long-term immunosuppression would address these issues. Adoptive immunotherapy with regulatory T cells (TREG) provides such an opportunity, as they own the potential to suppress a broad spectrum of immune cells. Since TREG cell activation via the T cell receptor (TCR) is essential for their suppressive ability, TCR specificity of TREG cells is important for their performance during clinical application. Therefore, antigen-specific TREG cells with the specificity for alloantigens, referred to as (allo)antigen-specific TREG cells, are favoured over polyclonal TREG cells for tolerance induction. The major aim of this PhD-thesis was to study the potential of receptor engineered (allo)antigen-specific TREG cells in models of skin transplantation and GvHD. One way to achieve (allo)antigen-specificity was the genetic modification of ex vivo expanded TREG cells of CBA/JRj mice (haplotype H2k), using (allo)antigen-specific TCR gene transfer. Alternatively, we transferred (allo)antigen-specific chimeric antigen receptors (CARs) into ex vivo expanded TREG cells. The later approach gave us the opportunity to generate (allo)antigen-specific TREG cells, independent of MHC restriction. Altogether, we were able to establish a long-term TREG cell line from CBA/JRj mice, referred to as ex vivo generated CBA TREG line. This cell line remained stable with respect to a variety of markers (surface and intracellular) and continued to express FoxP3 in vitro as well in vivo. In agreement with the herein described phenotype, the cell line was hyporesponsive and highly suppressive in vitro and in vivo. However, the long-term cultivated ex vivo generated CBA TREG line differed in several details from naïve TREG cells, e.g. sub-phenotype, chemokine receptor and adhesion molecule expression and TCR repertoire. Further, we could effectively generate (allo)antigen-specific TREG cells using TCR-gene transfer (OT II TCR). These cells displayed sufficient (allo)antigen-specific activation, expansion and in vitro suppression. Additionally, we here describe the engineering of (allo)antigen-specific CARs ([alpha]H-2Kb CAR and [alpha]SIINFEKL-H-2Kb CAR) and their use in the generation of (allo)antigen-specific CBA TRE
Septin remodeling is essential for the formation of cell membrane protrusions (microtentacles) in detached tumor cells by Kristine Østevold( )

1 edition published in 2018 in English and held by 17 WorldCat member libraries worldwide

Abstract: The vast majority of advanced metastatic disease is currently incurable. Consequently, metastasis is responsible for over 90% of the almost 9 million cancer related yearly deaths worldwide. In the pursuit of therapies aiming to inhibit metastasis, a detailed understanding of the different metastatic processes is of vital importance. Studies of detached tumor cells have described microtubule-based cellular protrusions called microtentacles with possible metastatic implications.<br><br>Here, we report that the formation of tumor cell microtentacles depends on the<br>presence and dynamics of small GTPases of the septin family, which are part of the cytoskeleton. In matrix-attached breast, lung, and pancreatic cancer cells, septins are associated with the cytosolic actin cytoskeleton. Detachment of cells causes redistribution of septins to the membrane, where microtentacle formation occurs. <br><br>The small GTPase Cdc42 and its effector proteins Borg regulate septins and are essential for microtentacle formation. We observed a close association of Borg with the septin cytoskeleton, both in attached and detached breast cancer cells. Additionally, we show that dominant active and negative Cdc42 inhibit microtentacle formation indicating that the free cycling of Cdc42 between its active and inactive state is essential for septin regulation and microtentacle formation.<br><br>Furthermore, inhibition of septins using forchlorfenuron in cell attachment and<br>aggregation models suggest that septins play an essential role in the metastatic<br>behavior of tumor cells, possibly attributed to a decrease in microtentacle formation. Our data propose septins as promising targets for novel anti-metastatic therapies.<br><br>Using a recombinant human septin complex, we induced septin filament<br>formation in vitro, and suggest a method to identify septin filament-binding proteins. Such studies could give new insight into the roles of septins in microtentacle formation and septin biology in general.<br><br>Last, by highlighting important structural and functional similarities, we reason<br>that toxin-induced protrusions serve as a potent experimental model for<br>microtentacles
Contributions of prefrontal cortex subsections to response inhibition by Stefanie Hardung( )

1 edition published in 2018 in English and held by 17 WorldCat member libraries worldwide

Abstract: In everyday life altering environmental conditions require flexible adaptation of planned or already initiated actions. Humans and animals are forced to constantly update their behavior to avoid maladaptive actions. Studies linked responseinhibition deficits to several neurological diseases and emphasized the critical role of the PFC for appropriately timed actions (Aron, 2011; Aron et al., 2014a; Chambers et al., 2009). These neuropsychiatric disorders include fronto-temporal dementia (Pompanin et al., 2014), and Parkinson's disease (Gauggel et al., 2004).<br>In the present thesis we investigated two mechanisms of motor inhibition: reactive and proactive stopping. We combined optogenetic and electrophysiological techniques to analyze the functional role of five key subareas of the rat medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC) in a response-preparation task (Eagle and Baunez, 2010; Wallis, 2011; Uylings et al., 2003). We observed two main effects following optogenetic inhibition of mPFC and OFC subareas: (1) inactivation of mPFC induced drastic changes during proactive behavior, and (2) OFC inhibition significantly impaired the rats' reactive motor control. Specifically, while prelimbic cortex (PL) inhibition induced an increase of premature responses, infralimbic cortex (IL) inactivation resulted in a decreased number of early lever releases. In contrast, optogenetic inhibition of OFC subareas (mainly the ventral orbitofrontal cortex (VO)) significantly impaired the rats' ability to respond rapidly after external cues. Additionally, we designed and optimized optrodes for combined optogenetics and electrophysiology in behaving rats. We compared a selection of commercially available as well as custom-made optrodes which are appropriate to target specific PFC subareas. These devices were implanted and subsequently used for electrophysiological recordings in task performing rats implemented. Consistent with our optogenetic experiments, task modulated PL units showed significantly reduced activity before early releases, while the opposite was true for the average of all recorded IL neurons. Further, principal component alanysis (PCA) of VO activity revealed strong components around the tone and reaction time (RT) window of correct trials, which supports the role of this lateral OFC subregion during the reactive phase of the task. Our data argue for opposing roles of IL and PL in directing proactive behavior and argue for an involvement of OFC in predominantly reactive motor control. By attributing defined roles to rodent PFC sections, this study represents a good starting point for future experiments (Jäckel, 2017; Herold, 2018) investigating further descending targets of the complex neural network involved in inhibitory processes
Characterisation of the DNA endonuclease subunit EME1 as novel substrate of sumoylated Ubc9 by Jan Rettich( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Abstract: Sumoylation of yeast homolog of ubiquitin-conjugating enzyme Ubc9 (Ubc9), the only E2 conjugating enzyme of the sumoylation pathway, can regulate small ubiquitin-like modifier (SUMO) substrate discrimination. A screen for novel substrates of sumoylated Ubc9 identified homolog 1 of Schizosaccharomyces pombe essential meiotic endonuclease 1 (EME1) and homolog of Sacharomyces cerevisiae SLX4 structure specific endonuclease subunit (SLX4) as enhanced modified substrates of sumoylated Ubc9. This proteins are subunits of the heterodimeric DNA endonucleases MUS81-EME1 and SLX1-SLX4 and are involved in homologous recombination during mitosis. This thesis aimed to investigate the regulation of the DNA endonuclease subunit EME1 with regard to a possible regulation by sumoylation. In addition, the regulation of Ubc9 sumoylation was also investigated. <br>The properties of EME1 sumoylation by sumoylated Ubc9 were investigated in vitro. Important motifs of EME1 sumoylation were mapped using a mutagenic approach. The lysine 27 was demonstrated to be the major consensus site lysine for in vitro sumoylation. Additionally, a SIM motif required for sumoylation by sumoylated Ubc9 was identified. Fluorescence studies revealed an influence of the sumoylation of EME1 on its localisation. Investigation of camptothecin resistance in cells, ectopically expressing different EME1 variants, demonstrated enhanced resistance of cells expressing a sumoylation mimicking mutant of EME1. This indicates that EME1 sumoylation is required for an efficient DNA repair. <br>Investigation of the regulation of Ubc9 sumoylation revealed that Ubc9 sumoylation is upregulated during mitosis. This coincides with the peak activity of the tetrameric complex composed of MUS81-EME1 and SLX1-SLX4. <br>In summary, this thesis characterised EME1 as a novel substrate for sumoylated Ubc9 and demonstrated that EME1 sumoylation reduces the sensitivity of cells to camptothecin
Der Tumorsuppressor APC/CCdh1 und seine Rolle bei der Entstehung von Replikationsstress und genetischer Instabilität by Julika Hohler( )

1 edition published in 2018 in German and held by 17 WorldCat member libraries worldwide

Abstract: Introduction: Progression through the cell cycle is tightly regulated by different cyclin-dependent kinases and their activating cyclin subunits. Stage-specific proteolysis of cyclins and other cell cycle regulators is important for transition to the next cell cycle phase. The anaphase-promoting complex/cyclosome (APC/C) is an E3-ubiquitin ligase that controls mitosis and G1 through degradation of these proteins. Through its activating subunits Cdh1 and Cdc20 the APC/C assures substrate-specifity. While Cdc20 regulates progression through mitosis, Cdh1 is activated in late mitosis to coordinate accurate entry into S-phase. Thereby, the APC/C is crucial for maintaining genomic stability during the cell cycle.<br>Results: Characterization of a Cdh1-kd revealed strong stabilization of the substrates cyclin A/B leading to diminished loading of mini-chromosome maintenance (MCM) proteins on replication origins in G1. Stabilization of cyclin A/B may cause the observed premature entry into S-phase, while the reduced loading of MCMs in G1 could be responsible for the prolonged replication in S-phase seen in Cdh1-kd cells. Plk1 was stabilized in Cdh1-kd cells, which may cause bypass of the Cdh1-Plk1 dependent DNA damage checkpoint. Indeed, potential replication stress in Cdh1-kd cells did not lead to G2/M arrest, but was enforced by inhibition of the Cdh1 substrate Plk1. Underreplicated DNA and replication intermediates in mitosis may be the reason for increased genomic instability, namely lagging chromosomes, anaphase bridges and micronuclei in Cdh1-kd cells detected by live-cell imaging. Monitoring of 53BP1, a DNA-repair marker, in living cells could also prove amplified DNA-damage through increased double-strand breaks in Cdh1-kd cells. In addition, aberrant cytokinesis and the development of tetraploid cells generated by misseparation of chromosomes during mitosis were enhanced in Cdh1-kd cells.<br>Conclusions: Downregulation of the tumor suppressor APC/C-Cdh1 leads to deregulation of DNA-replication by stabilizing cyclin A and B in G1 and reduced loading of replication origins with MCM proteins resulting in enhanced genomic instability
Regulation by the sRNA IsaR1 and transcriptome remodelling under iron starvation in Synechocystis sp. PCC 6803 by Gergana Kostova( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Identification and characterization of novel centromeric proteins in Drosophila Melanogaster by Georg Otto Milan Bobkov( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Signaling cascades of the Aspergillus fumigatus virulence factor Gliotoxin in mediating apoptosis and invasive aspergillosis by Florian Haun( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Abstract: Gliotoxin (GT) ist der zentrale Virulenz Faktor des Schimmelpilzes Aspergillus fumigatus (A.f.) und verantwortlich für die Manifestation von invasiver Aspergillose (IA) in immunsupprimierten Patienten. Die Invasivität von A.f. beruht hierbei auf dem GT-induzierten Verlust der Barrierefunktion des Lungenepithels. GT-induzierte Apoptose von Epithelzellen könnte in diesem Zusammenhang eine wichtige Rolle spielen.<br>Ziel dieser Arbeit war es die GT-abhängigen, pro-apoptotischen Signal Kaskaden zu charakterisieren. GT aktiviert die GTPase RhoA, welche über die nachgeschaltete Kinase ROCK, die folgende Kinase-Kaskade stimuliert: ROCK phosphoryliert die MAPK Kinasen MKK4 und MKK7, welche wiederum JNK phosphorylieren und somit aktivieren. Diese Kaskade endet mit der JNK-abhängigen Phosphorylierung von Bim und der damit verbundenen Freisetzung von Bcl-2. Bim ist dann in der Lage mit dem Effektor Protein Bak zu interagieren, um die GT-induzierte Perforation von Mitochondrien und somit Zelltod umzusetzen. <br>In diesem Zusammenhang fungiert ROCK als eine pro-apoptotische MAPKK Kinase, zusätzlich zu seiner bekannten Funktion in der Regulation von Zellmorphologie. Dementsprechend wurde gefunden, dass Zellen resistent gegen GT induzierte Apoptose waren, wenn sie (i) mit JNK oder ROCK Inhibitoren behandelt wurden, oder (ii) ROCK oder MKK4/7 genetisch reduziert beziehungsweise ausgeschaltet waren.<br>Interessanterweise bewirkt GT das Ablösen von Zellen. Dieser Vorgang kann den programmierten Zelltod einleiten und wird dann als Anoikis bezeichnet. Wir konnten zeigen, dass GT direkt relevante cysteine in der Ligandenbindungsdomäne von Integrin [alpha]V[beta]3 modifiziert. Zusätzlich inaktiviert GT Integrine, um Anoikis zu vermitteln. Integrin Inaktivierung induziert die Inhibition der Focal Adhesion Kinase (FAK) und des nachgeschalteten Faktors p190RhoGAP, um die RhoA abhängige Signal Kaskade zu stimulieren. Somit wirkt GT als ein neuartiger und physiologischer Stimulus, um Anoikis zu induzieren und Integrin-abhängige Signaltransduktion zu studieren.<br><br>Wir zeigen, dass ROCK Inhibitoren sowohl den GT-induzierten Zelltod als auch das Ablösen von Zellen verhindern konnten und daher in der Lage waren, die Epithelzell-Morphologie zu erhalten. Da diese beiden Mechanismen ursächlich für die GT vermittelte Invasivität von A.f. sein könnten, könnte die pharmakologische Inhibition von ROCK eine interessante Strategie zur Bekämpfung von IA
PRC2 during T cell development and activation by Jonas Marcello( )

1 edition published in 2017 in English and held by 17 WorldCat member libraries worldwide

Abstract: Cellular development and differentiation is characterized by finely tuned regulation of gene expression. The maintenance and ability to inherit gene expression pattern to daughter cells is - in part - controlled via epipgenetic mechanisms. One important epigenetic process is the trimethylation of the two antagonistic histone tail residues H3K4 and H3K27. While the former is associated with actively transcribed genes, H3K27me3 is mostly found among silenced genes. Some gene promoters, however, are associated with both H3K4me3 and H3K27me3 and those bivalent genes are mostly among key lineage defining transcription factors.<br>One key iNKT cell-lineage defining gene is Plzf (Zbtb16). The Plzf gene is bivalently modified (H3K4me3+ and H3K27me3+) in psDP cells, right before the cellular fate decision between conventional [alpha][beta] T cell or iNKT lineage restriction. In order for psDP cells to express Plzf and differentiate into iNKT cells, a strong TCR signal is required. This work shows that the expression of Plzf is accompanied by the transition of the Plzf promoter from a bivalent to a monovalent H3K4me3 state. The removal of H3K27me3 is an essential prerequisite for Plzf activation and subsequent iNKT cell development. Artificial removal of H3K27me3 through deletion of the H3K27 methyltransferase Ezh2 causes the development of iNKT cells, even in the absence of iNKT-lineage directing strong TCR signaling events.<br>In addition to its well described nuclear function, we also discovered a cytosolic form of the PRC2 complex that is involved in TCR signaling. The cytosolic PRC2 complex is essential for proper TCR signal propagation through the MAPK pathway and absence of PRC2 prevents the activation and proliferation of naive CD4 T cells. Interestingly, this defect is very specific and affects only the proper activation of the pro-survival cytokine IL2, while other T cell response gene are unaffected and induced normally
Norf1 - a novel, small protein that possibly regulates the activity of Synechocystis sp. PCC 6803 ATP synthase by Desirée Baumgartner( )

1 edition published in 2017 in English and held by 17 WorldCat member libraries worldwide

Abstract: In the model cyanobacterium Synechocystis sp. PCC 6803, hundreds of transcripts were found that originate from genomic regions without annotation, suggesting their association with novel and unexplored functions. Some of these transcripts are non-coding RNAs with regulatory functions, while others are short mRNAs, encoding µ-proteins (proteins ≤80 amino acids). Six examples, called norf1, nsiR6, hliR1, norf4, ssr1169 and ssl2823, which were supposed to belong to the latter category, exhibited intriguing modi of expression and appeared as promising candidates for further investigation. First the expression patterns of norf1, nsiR6 and hliR1, which were expected to be specifically expressed under a certain condition, as well as the expression of norf4 in response to nitrogen starvation was studied in more detail. A previously supposed upregulation of norf1 expression in the dark could be verified via Northern blot analysis. Likewise, the nsiR6 transcript was highly induced under nitrogen starvation. The norf4 mRNA was found to overlap the gap1 mRNA on the complementary DNA strand by several hundred nucleotides. Both mRNAs showed a mild upregulation upon the removal of nitrogen, suggesting a co-regulation of the two transcripts. The expression of hliR1 was highly induced under high light and seemed to be associated with sodB expression. To verify the coding potential of the six transcripts, the translation of the predicted small open reading frames (sORFs) was pursued by the construction of mutant strains expressing FLAG-tagged versions and subsequent immunoblotting. After induction of expression via the Cu2+-responsive petE promoter or from their native promoters, all six <br>µ-proteins were detected.<br>The work then focused on the functional characterization of the previously unknown small protein Norf1, which attracted particular attention due to its high expression in the dark distinguishing it from the vast majority of genes. A loss of function mutant and several overexpression strains were generated to screen different environmental conditions in the course of physiological characterization. Affinity purification of FLAG fusion proteins and subsequent mass spectrometry analysis identified ATP synthase subunits as putative binding partners of Norf1. This was further substantiated by finding AtpB to be co-purified with FLAG-tagged Norf1 and Norf1 to be co-purified with FLAG-tagged AtpB in the inverted approach, indicating a possible regulatory role of Norf1 on ATP synthase in Synechocystis sp. PCC 6803.<br>The results obtained in this work emphasize the importance of small proteins and why it is worthwhile to explore their versatile functions, especially in cyanobacteria
Regulation of cell survival by host and viral anti-apoptotic Bcl-2 proteins by Michaela Ohmer( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Abstract: Apoptosis is a conserved mechanism of metazoans that does not only eliminate damaged or defective cells and serves to maintain homeostasis in an organism, but it is also initiated as a response to viral infection. However, the signals from the recognition of viruses to apoptosis of an infected cell and the host factors that regulate this cell death are not completely understood. In this study we illustrate the participation of the Bcl-2-like proteins Bcl-XL and Mcl-1 in virus infection - both two major anti-apoptotic proteins of the host cell that are crucial for cell survival. When epithelial cells and fibroblasts were infected with modified vaccinia virus Ankara (MVA), the protein levels of Mcl-1 decreased, in contrast to its mRNA levels, suggesting a post-transcriptional regulation or enhanced degradation. Additionally, we were able to show that the protein could be replaced functionally by the viral anti-apoptotic Bcl-2-like protein F1L upon ABT-737-induced apoptosis in MEFs and upon knockdown or inhibition of Mcl-1 in HeLa. When cells were infected with vaccinia virus (VACV), which also expresses F1L, similar results were obtained. Protein levels of Mcl-1 were not reduced after infection with murine cytomegalovirus (MCMV), but ABT-737-induced apoptosis was also inhibited by a Mcl-1-like activity.<br>Murine macrophages were infected with MVA, VACV, MCMV and influenza A virus, and in contrast to epithelial cells or fibroblasts, infection resulted in apoptosis. Mcl-1 deficient macrophages showed no difference in apoptosis induction compared to wild type upon infection with MVA, VACV or MCMV, whereas Bcl-XL deficiency or treatment with ABT-737 substantially increased cell death in infected cells. Additionally, absence of Bcl-XL or ABT-737 treatment reduced the generation of infectious VACV particles. These data indicate that regulation of pro-apoptotic signals during infection with different large DNA viruses does not depend on Mcl-1. In fibroblasts and epithelial cells, Mcl-1 can be functionally replaced by viral proteins such as F1L, whereas in macrophages the induction of apoptosis upon viral infection seems not be blocked by Mcl-1. In contrast, Bcl-XL is important for the survival of the virus-infected macrophage and its presence can determine the outcome of the infection since it influences the production of viral particles.<br>Since the viral protein F1L has critical functions of preventing apoptosis, its regulation and interaction with cellular proteins is crucial for the outcome of the infection. In order to find possible interaction partners, we performed experiments using SILAC, revealing potential candidate proteins that influence the stability of F1L as well as the regulation of Mcl-1 during viral infection. Whether these proteins are real interaction partners of F1L and whether they are able to manipulate the outcome of viral infections will be the aim of future studies
Inference of multi-scale connectivity in the brain by Jonathan Schiefer( )

1 edition published in 2018 in English and held by 17 WorldCat member libraries worldwide

Abstract: The brain consists of neurons which are interconnected by synapses. The connectivity of the networks formed by the neurons and synapses is a key feature for the function and dysfunction of the brain. In humans, studying the connectivity comes with various challenges. Thus, the access to connectivity in humans is limited. The aim of this dissertation is to introduce a novel method to estimate effective connectivity of neural populations from continuous recordings of the activity of these populations which overcomes limitations of existing methods. This method estimates the connectivity of neural populations based on the covariance of the measured activity. The key mechanism for doing so is a L1 -minimization via a gradient descent on the manifold of unitary matrices. The fact that the gradient of a matrix on the unitary manifold is skew-hermitian and with this in the corresponding Lie-Algebra, is exploited in the update step to project the gradient back on the manifold via the exponential map. As presented in this thesis, this method works reliably for sparse networks with more than 40 nodes and a sufficient network interaction. The method can be applied on zero-lag covariance matrices, hence there is no restriction on the sampling rate of the measurement. Although based on a linear interaction model, the method also achieves reasonable results for networks which interact non-linearly. A comparison with structural measures based on fMRI data shows better agreement than state-of-the-art methods. Also, the method is robust against noise, unobserved nodes and variable hemodynamics of BOLD signals. In this thesis, a novel method for the estimation of effective connectivity from covariances of neural activity is presented. The features of this method make it applicable on a broad range of data-types, including data based on the BOLD effect or electro physiologic data such as ECoG. Applications of fast fMRI data show plausible and coherent results
Precise and sustained gene silencing in CD4+ cells using designer epigenome modifiers as a therapeutic approach to treat HIV infection by Tafadzwa Mlambo( )

1 edition published in 2018 in English and held by 16 WorldCat member libraries worldwide

Die Plastizität des Nukleoproteins von Influenza-A-Virus erlaubt unterschiedliche Strategien dem antiviralen Effekt der Mx- Proteine auszuweichen by David Martin Riegger( )

1 edition published in 2015 in German and held by 16 WorldCat member libraries worldwide

Sex-specific transcript complexity in the neural system of Drosophila melanogaster by Carmen Mohr( )

1 edition published in 2016 in English and held by 16 WorldCat member libraries worldwide

Abstract: Post-transcriptional alternative splicing (AS) of precursor messenger RNA (pre-mRNA) is a fundamental process in the gene expression cascade. Via alternative splicing, transcriptome and proteome diversity is massively increased in higher organisms, and recent studies revealed that over 95 % of human and 60 % of Drosophila genes are alternatively spliced (Graveley et al., 2011; Pan et al., 2008; Wang et al., 2008). However, in general little is known about the impact of AS on developmental processes, about regulatory mechanisms underlying AS, and about the biological role of alternative transcripts. The sex determination pathway of Drosophila serves as a prime example and is the best analyzed splicing network to date. Sex-lethal (Sxl) as the master regulator on top of the sex determination cascade directly regulates sex-specific AS of its own transcript and the pre mRNAs of male-specific lethal 2 (msl-2) which is crucial for dosage compensation, and transformer (tra) encoding another splicing factor (Bashaw & Baker, 1995; Bell et al., 1991; Inoue et al., 1990; Kelley et al., 1997; Nagoshi et al., 1988). Subsequently, Tra together with Transformer2 (Tra2) controls AS of doublesex (dsx) and fruitless (fru) which in turn encode sex-specific transcription factors (Burtis & Baker, 1989; Ito et al., 1996; Ryner & Baker, 1991; Ryner et al., 1996). <br>In this thesis, Drosophila was used as a model organism to explore the level of sex-specific transcripts in the neural system, to investigate the regulation of AS, and to explore the biological relevance of these transcripts. For this purpose, genome-wide approaches were combined with in vivo genetic and molecular studies. Whole-transcriptome RNA-Sequencing (RNA-Seq) analyses revealed that many more genes besides the classical sex determination factors are sex-specific alternatively spliced in the adult fly head. Further experiments showed that these AS changes are not significantly influenced by signals of the germline or factors which are transferred during mating. The absence of sex-specific transcripts in third instar larval brains further supported the idea of a functional relevance of sex-specific transcripts in adult fly heads. <br>As for most of these alternatively spliced transcripts no prove of functional isoforms already existed, we investigated whether sex-specific isoforms of one of our candidate genes, Tango13, fulfill specific functions. Firstly, we showed that Tango13 transcripts encode two sex-specific protein isoforms. Next, we illustrated the potential of alternative Tango13 isoforms to influence the behavior of the fly in a sex-specific manner. We postulate that in the case of Tango13, sex-specific AS might also interfere with signaling via the sulfation pathway.<br>Using dual-fluorescence reporter minigenes to monitor AS in vivo, we observed the exciting phenomenon of tissue-specific regulated isoform expression. Often, one isoform was exclusively expressed in one tissue, whereas the alternative isoform was expressed in another tissue. While this observation hindered the assessment of sex-specific isoform levels, we investigated cis- and trans acting regulatory elements underlying tissue-specific AS of Tango13. Here, ELAV was identified as a potential trans-acting regulator of Tango13 alternative splice site choice. <br>Taken together, in this thesis I could show that sex-specific AS targets various other genes next to the classical sex determinants, has important biological functions, and features interesting regulatory mechanisms
Dissection of the human centromere epigenetic propagation pathway in a novel cell-based heterologous system by Evelyne Janine Chantal Barrey( )

1 edition published in 2017 in English and held by 16 WorldCat member libraries worldwide

Initial assembly steps of the twin-arginine translocation signal peptide receptor complex by Anne-Sophie Blümmel( )

1 edition published in 2016 in English and held by 16 WorldCat member libraries worldwide

Phosphorylation of Beclin 1 by BCR-ABL suppresses autophagy in CML by Chuanjiang Yu( )

1 edition published in 2016 in English and held by 16 WorldCat member libraries worldwide

Abstract: The constitutively active chimeric tyrosine kinase BCR-ABL is critical for initiation, progression and maintenance of chronic myelogenous leukemia (CML). Imatinib and second-generation BCR-ABL tyrosine kinase inhibitors (TKIs) serve now as standard therapies for Ph+ patients. However, disease persistence occurs frequently and one of the major reasons was considered to be insensitivity of CML stem cells to TKI treatment.<br>Recently accumulated evidence argues that, autophagy, a genetically regulated process of adaptation to metabolic stress, is involved in TKI-induced cell death. It is hypothesized, that TKI-induced autophagy could allow CML stem cells to become metabolically dormant enabling their survival under conditions that may mimic growth factor deprivation and thereby "counter" TKI-induced cell death. However, the molecular mechanism of TKI-induced autophagy in BCR-ABL+ CML, as well as its role in malignant progression is poorly understood.<br>It has been shown that autophagy functions in CML in vitro, however, les is known in vivo. This study aimed to identify the precise role of autophagy and its effector molecules in a murine CML model. To identify the impact of autophagy in BCR-ABL-driven leukemia, a targeted genetic approach to knockdown Beclin 1 as a key regulator of autophagy in a CML mouse model was used. Interestingly, mice transplanted BCR-ABL expressing bone marrow harboring Beclin 1 knockdown showed a less aggressive disease with significantly lower WBC-count, leukemic burden and prolonged overall survival of the mice compared to mice transplanted with BCR-ABL + Beclin 1 WT BM. <br>To further test whether BCR-ABL regulates autophagy, LC3 was measured as a marker for autophagy in BCR-ABL+ K562 cell. Interestingly, inhibition of BCR-ABL activity by nilotinib led to increased LC3-II expression and punctual LC3 accumulation, indicating that BCR-ABL activity can suppress autophagy. Next, the proteins involved in BCR-ABL mediated autophagosome formation were investigated. Recruitment of VPS34, UVRAG and ATG14 to Beclin 1 was increased in case of nilotinib treatment and could thereby positively regulate autophagosome formation, whereas Rubicon, a negative regulator, was recruited less frequently to the Beclin 1 complex.<br>To further clarify the function of Beclin 1, biochemical analyses were performed. It showed that Beclin 1 binds to BCR-ABL independent of BCR-ABL kinase activity and Beclin 1 is phosphorylated by BCR-ABL. To test the impact of BCR-ABL mediated Beclin 1 phosphorylation on autophagy induction, Beclin 1 phospho-mimic (Y233E/Y352E) and phospho-deficient (Y233F/Y352F) mutations were generated. Interestingly, nilotinib treatment failed to induce autophagy in cells expressing the Beclin 1 phospho-mimic mutation, thereby highlighting the necessity of Beclin 1 in BCR-ABL-mediated autophagy. Expression of Beclin 1 mutants in Beclin 1 knockout MEFs and K562 cells showed decreased binding of UVRAG, ATG14 and VPS34 to Beclin 1 Y233E/Y352E, suggesting an important role of Beclin 1 phosphorylation for complex stabilization and autophagy suppression. Interestingly, phospho-deficient Beclin 1 also delays BCR-ABL-driven leukemogenesis, demonstrating that Beclin 1 phosphorylation is crucial for BCR-ABL-mediated leukemogenesis. In contrast, deletion of Atg5, another central regulator of autophagy, did not impede disease onset or progression in the CML model.<br>Taken together, these findings identify Beclin 1 as a specific substrate of BCR-ABL, thereby highlighting the importance of Beclin 1 in BCR-ABL-mediated leukemogenesis and showing that autophagy induction in CML cells may be rather a specific Beclin 1-BCR-ABL interaction effect than a general microenvironmental stress phenomenon
Study of Z-disc-associated signaling networks in skeletal muscle cells by functional and global phosphoproteomics by Lena Reimann( )

1 edition published in 2016 in English and held by 16 WorldCat member libraries worldwide

 
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Alternative Names
Albert-Ludwigs-Universität Freiburg Faculty of Biology

Faculty of Biology

Fakultät für Biologie

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English (18)

German (2)