International research contends that school counselors are uniquely positioned to support the mental health needs of children and youths in schools yet face multiple challenges such as misconceptions about their roles. This doctoral research seeks to contribute to the field of school counseling research by investigating school counselors in the Kingdom of Bhutan where school counseling services were recently implemented but have yet to be examined. To address this knowledge gap, three studies were carried out to explore the most important challenges faced by school counselors in Bhutan. First, a systematic literature review investigated the most prevalent needs of school counseling services in East and Southeast Asia which retrieved 109 studies from 14 countries. The analysis and summary of results revealed nine areas of need affecting school counseling services in this region of the world, the three most important being the need for up-to-date training, the need for a model of counseling practice and the need to overcome stigma towards mental health issues. Second, a survey of 162 of the 179 school counselors registered in the Kingdom of Bhutan investigated their daily tasks, their roles and responsibilities including how these are perceived by 65 of their colleagues, namely, 49 school teachers and 16 school principals, and their challenges and resources. Significant differences on the International Survey of School Counseling Activities (ISSCA) (Carey et al., 2020) revealed confusion in the roles and responsibilities perceived by school counselors and their colleagues. A Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis of responses to open-ended questions further revealed that school counselors were hindered by insufficient initial training, by the need for material resources such as a counseling room, by insufficient time and opportunities for students to see the school counselor and by the issue of stigma towards mental health issues. Third, online and in-person interviews of 28 Bhutanese school counselors investigated, using thematic analysis by Braun and Clarke (2006), their perceived challenges and resources in more depth. Results both confirmed the review and survey study findings and revealed further challenges potentially unique to Bhutan such as the need for one female and one male school counselor in every school. Triangulation of results guided by Bronfenbrenner’s Ecological Systems Theory (Bronfenbrenner, 1995) revealed Bhutanese school counselors’ 12 most important challenges. These are (1) role confusion, (2) the lack of communication and collaboration with stakeholders, (3) the lack of initial training, (4) the lack of supervision, (5) the role of the COVID-19 pandemic, (6) the role of stigma towards mental health issues, (7) the importance and lack of social support, (8) the role of corporal punishment in Bhutanese schools, (9) the lack of material resources, (10) the need for one female and one male school counselor in each school, (11) the lack of time and opportunities for students to see the school counselor, and finally (12) that the school counseling profession is still relatively new and needs time to establish itself. While these results shed light on the phenomenal efforts of school counselors in the Kingdom of Bhutan, they also serve to illustrate a profession that is as complicated as it is systematically isolated and disempowered, ultimately hindered from achieving its potential to support Bhutanese children and youths’ mental health. The findings of this doctoral research contribute to global research on school counseling, suggest new research paths, such as the need to investigate students’ experiences of school counseling services, and propose specific policy changes to improve school counseling in Bhutan.
Weniger anzeigenChronic Tinnitus denotes the longstanding, conscious awareness of a tonal or composite noise for which there is no identifiable external acoustic source. Depending on the psychological makeup of affected individuals, tinnitus can be highly distressing. Current guidelines view the symptom together with its cognitive-emotional processing as a psychosomatic phenomenon – and suggest (1) medico-audiological treatment for underlying medical influences – if known, and (2) psychological treatment for highly distressed individuals. Anchored within a psychosomatic vulnerability-stress-coping framework, the present thesis sets out to examine chronic tinnitus-related distress. It asks two questions: 1. In how far do direct or indirect psychological factors – that may or may not correlate with ‘somatic’ variables – influence individuals’ experience of a tinnitus symptom as distressing? And: 2. In how far are psychosomatic (i.e. psychologically or medico-audiologically anchored) treatment approaches effective in ameliorating tinnitus-related distress? Chapter 1 [Introduction] briefly reviews evidence on vulnerability-stress-coping contributors to chronic tinnitus symptomatology and related distress-reactions. Chapter 2 [Vulnerability] presents the first two studies of the thesis, which examine chronic tinnitus-related distress at the junctions of (1) biological markers of tinnitus symptom vulnerability or perceived stress experiences and (2) psychological vulnerability-stress interactions. Chapter 3 [Stress] presents the third study, which investigates, whether transdiagnostically relevant psychological variables underlie chronic tinnitus- and pain-related distress experiences. Chapter 4 [Coping] examines the efficacy of psychosomatic treatment approaches. The final three studies of this thesis examine (1) whether a transdiagnostic psychological treatment approach ameliorates different functional symptom clusters, (2) whether a ‘somatic’ treatment approach (hearing amplification) bears psychological benefit, and (3) psychological effects on hearing amplification via hearing aid use-time. Chapter 5 [General Discussion] summarizes the presented papers and discusses theoretical and clinical implications.
Weniger anzeigenEntanglement is a fundamental principle in quantum mechanics, and is known for its crucial part in quantum information science and quantum communication, among others. In attosecond science, the possible effects of entanglement in light-matter interaction are receiving more and more attention. In this research field, typically radiation in the extreme ultraviolet (XUV) or x-ray regime is used to study time-dependent dynamics in time-resolved spectroscopy experiments. The high photon energy of this radiation leads to ionization of any sample placed in the way, thus creating multicomponent quantum systems with possible entangled subsystems, e.g. ion and photoelectron. Entanglement between the subsystems can have measurable effects on the outcome of an experiment, and can even prevent the observation of time-dependent observables. This notion is most prominent if the experiment includes only measurements in one of the subsystems, which means for example in the case of molecular photoionization, that only the ion or photoelectron is measured. This setting leads to interesting questions about the role of entanglement in attosecond photoionization processes. In particular, what is the role of entanglement between the ion and departing photoelectron regarding the observability of coherence-based dynamics in the ion? Furthermore, is it possible to control the degree of coherence in the ion and the degree of ion+photoelectron entanglement, respectively, by alternating the pulse properties of the ionizing pulses? To answer these questions, an experimental protocol is described in this thesis, which utilizes two phase-locked XUV pulses together with a near-infrared pulse (NIR) to dissociatively ionize hydrogen molecules. The main experiments presented here investigate the impact of entanglement between the cation and photo- electron, first on vibrational coherence, and subsequently on electronic coherence created in H2+. In the first experiment, a pair of phase-locked XUV pulses creates a vibrational wave packet in the 1sσg state of H2+ , which is subsequently probed by the NIR pulse dissociating the ion. The spectral properties of the ionizing pulses are tailored by alternating the delay between the two XUV pulses, thus controlling the degree of vibrational coherence and the degree of ion+photoelectron entanglement, respectively. In the second experiment, the two XUV pulses create an entangled ion+photoelectron system during the dissociative ionization of H2. The NIR probe pulse can subsequently project the initially entangled system into a coherent superposition of the first gerade (1sσg) and ungerade (2pσu) electronic states of the H2+ cation. The ability of the NIR pulse to convert the initially entangled system into a coherent superposition of electronic states is controlled by changing the time delay between the ionizing XUV pulses. These studies show the crucial role of ion+photoelectron entanglement in attosecond science, especially in attosecond pump-probe experiments, and they present a first attempt to link ultrafast science with quantum information theory.
Weniger anzeigenThis study is concerned with the interdisciplinary analysis of representations of philosophy in 14thcentury England, particularly in works by Thomas Bradwardine and Geoffrey Chaucer, and the exploration of the intellectual and literary-aesthetic contexts in which these works have been placed. These contexts involve a conception of intellectual history that sees the 14th-century as dominated by a fierce polemic between the philosophical schools of nominalism and realism. Past scholarship has typically associated 14th-century nominalism with a progressive, humanist, and empiricist mind-set, and in this capacity has frequently portrayed nominalism as a precursor of the Renaissance and modernity. Realism, on the other hand, has been associated with a reactionary conservatism, and a clinging to increasingly outdated scholastic methods. Debates between nominalism and realism, also characterized as a ‘battle of the ways’ between a via moderna and via antiqua, were supposed to have resulted in a decisive nominalist victory. In this fashion, the ‘nominalist controversy’ has come to represent the symbolic enactment of a period shift from Middle Ages to Modernity. This conflict has been understood to have excited heated partisan debates not only amongst academics and theologians, but also in other cultural spheres, particularly that of literary production. While this model of intellectual history provides a clear and self-enclosed narrative of epochal transition, it has lately been subjected to withering critique: Not only has the ‘modernity’ of the canonical nominalists been called into question, even the notion that nominalism and realism can be said to represent distinct traditions of thought has now been largely abandoned by specialists. While these developments are increasingly absorbed in the field of the history of philosophy, they have had undeservedly little impact in other areas: In literary criticism, the methodology of the research paradigm of literary nominalism still dominates analyses on the role of philosophy in 14th century literary works. Literary nominalism perpetuates an obsolete model of intellectual history, which assumes nominalism to have embodied a proto-modern Zeitgeist. It heavily emphasizes analogic readings, and the ‘claiming’ of authors for either the nominalist or realist camp. It sees textual features like heteroglossia, play, openendedness, and irony as resulting from a nominalist mind-set, rather than inherent features of the literary text. Apart from its insistence on a nominalism / realism dichotomy, the way literary nominalism conceptualizes the interaction between philosophy and literature is also highly problematic, as it places literary works in a dependent hierarchical relationship to philosophy, allowing literature little generative force of its own. The central aims of this study are as follows: It contributes to the ongoing re-assessment of the 14th-century intellectual landscape through an analysis of Thomas Bradwardine’s De Causa Dei, and its place in the ‘nominalist controversy’. Bradwardine was frequently associated with a realist school and the via antiqua, and was placed in an antagonistic relationship to supposedly nominalist peers like William of Ockham. This study analyses the paradigm of literary nominalism, with the goal also of exposing the central flaws in its understanding of 14th century philosophy, its methodology, and in the relationship between philosophy and literature it proposes. It suggests potential methodological amendments, which are applied in a reading of Geoffrey Chaucer’s Canterbury Tales, whose interpretation was also heavily warped by the problematic application of literary nominalist theories
Weniger anzeigenPluripotency, where cells have the capacity to differentiate into all types of cells in the embryo, is a transient state in early embryonic development. Normally, it lasts for 2-3 days, but many animal species can undergo diapause to halt the development and retain pluripotency under unfavourable conditions. One way to induce the paused state is through inhibition of mechanistic target of rapamycin (mTOR). mTOR is a protein kinase that plays a central role in regulating cellular processes such as growth, metabolism, and autophagy with environmental inputs. Mouse embryos lacking mTOR failed to develop beyond the blastocyst stage. Overall, these indicate that mTOR plays a vital role in pluripotency regulation. However, the mechanisms remain unknown. In this study, I established and applied various biochemical, genetic and NGS technologies to investigate the role of nuclear mTOR in embryonic stem cells (mESCs). mTOR kinase activity was found to be essential for mESC differentiation and mTOR nuclear and chromatin localisation were observed. ChIP-seq experiments revealed that mTOR associates with the promoters of developmental genes at the chromatin in mESCs. In vitro kinase assay showed that mTOR is a histone H2A kinase, phosphorylating H2A at threonine 120 (H2AT120ph). Using integrative analyses of CUT&Tag and TT-SLAM-seq, I found that the level of H2AT120ph at mTOR-associated promoters and their nascent transcription transiently increases during pluripotency exit. These promoters had a high presence of polycomb repressive complex 1 (PRC1) and correlated with the polycomb histone marks, suggesting mTOR works closely with PRC to regulate gene expression. The results reveal a novel mechanism through which mTOR can regulate gene expression and may have implications in other developmental and disease contexts
Weniger anzeigenDiese Habilitationsschrift widmet sich dem Einfluss von sozialen Faktoren auf psychische Erkrankungen und ihre Behandlung: Dabei untersucht die erste Arbeit den Zusammenhang von verschiedenen Wohnformen und Wohnungslosigkeit unter (teil)stationär-psychiatrischen Patient*innen mit dem Fokus auf sozidemografische und klinische Faktoren, sowie das Nutzungsverhalten des Krankenhauses sowie des ambulanten psychosozialen Hilfesystems abhängig von der Wohnform. In der Arbeit zeigt sich, dass ein beträchtlicher Teil der Patient*innen in keiner eigenen Wohnung, sondern entweder auf der Straße, in Wohnungslosen- oder Flüchtlingsheimen (13 %) oder in sozialtherapeutischen Einrichtungen (18,3 %) lebt. Charakterisiert waren wohnungslose Patient*innen vor allem durch ein jüngeres Alter, einem früheren psychiatrischen Erstkontakt, männliches Geschlecht, niedrigeres Bildungsniveau und das Vorliegen einer Substanzgebrauchsstörung und psychotischen Störung. Die Ergebnisse unterstreichen den Bedarf nach alternativen und niedrigschwelligen Wohnangeboten für Menschen mit schweren psychischen Störungen. Weiterhin zeigen die Ergebnisse, dass wohnungslose Menschen in stationär-psychiatrischer Behandlung signifikant kürzere Behandlungszeiten aufweisen, im Kontrast zu anderen europäischen und nordamerikanischen Ländern. In der zweiten Arbeit untersuchten wir im Rahmen der Wohin-Studie finanzielle Belastungen und Schulden bei psychiatrischen Patient*innen, wobei eine signifikante Anzahl von Patient*innen (55,1 %) Schulden, Kredite oder offene Rechnungen aufwies. Substanzabhängigkeit und ein jüngeres Alter waren signifikant assoziierte Faktoren für das Vorliegen von Schulden. Finanzielle Belastungen und Verschuldung bei Menschen mit psychischen Erkrankungen sollten daher im klinischen Kontext stärker berücksichtigt werden. Die dritte Arbeit der Habilitationsschrift untersuchte im Rahmen eines systematischen Reviews mit Metaanalyse problematisches Glücksspielverhalten unter wohnungslosen Menschen. Die Prävalenzraten für problematisches Spielverhalten und Spielsucht waren dabei deutlich erhöht gegenüber Zahlen in der Allgemeinbevölkerung. Modelle zur Früherkennung und Behandlung von problematischem Glücksspiel sollten daher zunehmend entwickelt und implementiert werden insbesondere für vulnerable Gruppen. Die vierte Arbeit widmet sich der Nutzung von Mobiltelefonen und Computern bei Patient*innen in (teil)stationärer psychiatrischer Behandlung. Die Ergebnisse zeigen, dass die Rate des Besitzes von Smartphones (59,3 %) und der regelmäßigen Nutzung von Computern (68,4 %) unter den psychiatrischen Patient*innen niedriger war als in der Allgemeinbevölkerung. Wohnungslosigkeit, die Diagnose einer psychotischen Erkrankung, höheres Alter und ein niedriger Bildungsgrad waren signifikant assoziierte Faktoren damit kein Mobiltelefon zu besitzen bzw. keinen Computer zu nutzen. Zur Verhinderung digitaler Barrieren sollten diese Ergebnisse bei der Planung der digitalen Umgestaltung der Versorgungsangebote als auch Entwicklung von E-Health-Lösungen berücksichtigt werden. Die fünfte Veröffentlichung dieser Habilitationsschrift befasst sich mit der Wohnzufriedenheit in verschiedenen Wohnformen psychiatrischer Patient*innen, wobei die Wohnzufriedenheit signifikant höher ausfiel bei Personen, die eine eigene Wohnung zur Verfügung hatten oder Wohngemeinschaften nutzen im Vergleich zu Personen, die in stärker institutionalisierten Settings oder in Einrichtungen für wohnungslose Menschen lebten. Dies unterstreicht den Bedarf an unabhängigen Wohnformen mit flexiblen Hilfen für Menschen mit schweren psychischen Erkrankungen in Wohnungslosigkeit oder erhöhtem Risiko.
Weniger anzeigenEnvironmental degradation within river basins arises from both natural factors, such as climatic variability and biophysical attributes like topography and soil characteristics, as well as anthropogenic influences. Human-induced degradation, driven by factors such as population growth, urban expansion, and shifts in land use patterns, exacerbates the natural degradation processes. The study sought to model soil erosion risk in the Black Volta River basin. Specifically, the study (1) evaluated and determined the land use and land cover dynamic and drivers of urban expansion in the Wa municipality of Ghana between 1990 and 2020, (2) estimated soil erosion risk in a typical savannah landscape of Wa municipality of Ghana between 1990 and 2020 and (3) estimated and evaluated soil erosion risk across various landscape units of the Black Volta River basin over the periods of 1992, 2006 and 2020. Landsat satellite data (30 x 30 m resolution) was processed using Geographical Information System and remote sensing techniques to establish the spatial and temporal dynamics of land cover in the Wa municipality for the years 1990, 2001, 2010 and 2020. The thematic maps were used to assess the drivers of urban expansion (objective 1) and the potential and soil erosion risk (objective 2) in the Wa municipality. In the basin scale and landscape units’ erosion risk modelling for the years 1992, 2006 and 2020 (objective 3), a 300 x 300 m resolution land cover data from the Copernicus Global Land Cover Services was used. Based on the spatial and temporal analysis of land cover change, it was evident that settlement expansion led to the depletion of woody biomass over the three decades (1990 to 2020). Settlement expansion was influenced by accessibility and connectivity factors, such as distance to existing settlements, rivers, and primary, tertiary, and unclassified roads, which were established as predictors of settlement expansion in the Wa municipality. By employing the Revised Universal Soil Loss Equation model, potential erosion risk was higher in 1990 (mean annual rate = 8.5 t ha⁻¹yr⁻¹) due to higher rainfall erosivity compared to 2020 (6.5 t ha⁻¹yr⁻¹) when rainfall erosivity was lower. However, the estimated soil erosion risk was lower in 1990 (2.6 t ha⁻¹yr⁻¹) due to greater vegetation cover, compared to 2020 (3.1 t ha⁻¹yr⁻¹) when vegetation cover declined. Soil loss was notably high in settlement, urbanising and areas with long and steep slopes, emphasising the influence of human and topographic factors on high erosion risk. This was statistically validated with data from a field survey that measures the spatial extents of soil erosion damages in 2 km² each of settlement, open savannah and closed savannah areas in the Wa municipality. It was established that settlement areas were the most damaged followed by open savannah and closed savannah units. Statistical correlation analysis reveals a positive relationship between the spatial extent of damages and the predicted soil erosion risk rates from the RUSLE model. At the basin scale and across landscape units, erosion risk and soil loss are primarily driven by topographic attributes and rainfall erosivity factors. The Savannah Escarpment and Sahelian Highlands with steep slope characteristics were identified as extreme erosion risk landscape units, while the Low Sahelian Plains and Sahelian Uplands, characterised by flat and gentle slopes, were predicted to have low erosion risk. Also, localised concave areas in the Savannah Escarpment and Sahelian Highland coupled with low TWI characteristics further heightened erosion risk. Additionally, a positive increase in the rainfall erosivity factor resulted in a positive change in soil loss while a decrease in rainfall erosivity factor led to a negative change in soil loss across all the landscape units, thus, underscoring the influence of rainfall erosivity factor on high erosion risk. Overall, the findings enhance the understanding of the erosion risk dynamic in the Black Volta River basin and would serve as a guide in planning management practices in line with global goals that seek to ensure environmental sustainability.
Weniger anzeigenNon-O1/non-O139 Vibrio cholerae (NOVC) is a natural inhabitant of aquatic ecosystems. It can cause both intestinal and extraintestinal infections in humans through the consumption of contaminated food or direct contact with contaminated surfaces, such as seawater or sediment. Previous studies have identified virulence-associated genes in NOVC that may contribute to its ability to cause infections. This doctoral thesis aimed to characterize the virulence mechanisms of NOVC isolated from food and environmental sources. A literature review was conducted to explore the infection routes of NOVC and its virulence-associated gene profiles. The genes were then compared with whole genome sequences of NOVC isolates from seafood (63 strains) and the German sea coastline (31 strains) to determine the presence of virulence-associated genes. Phylogenetic analysis was also performed. Additionally, phenotypic tests, including biofilm formation, hemolytic activity, motility, and serum resistance, were carried out to further validate the genetic findings. The antimicrobial resistance (AMR) of NOVC was also examined at both the genetic and phenotypic levels. Virulence-associated genes were classified into five stages, representing the infection process from ingestion to detachment from the human host. Most of these genes were detected in NOVC isolates from both food and environmental sources, including key toxin-encoding genes (hlyA, rtxA, chxA, stn), pathogenicity islands (VPI-2 and VSP-2), and secretion systems (T3SS and T6SS). A close core genome relationship was observed between the NOVC strains in this study and clinical NOVC strains. Notably, all NOVC strains exhibited increased motility at 37°C compared to 25°C, and most were capable of forming strong biofilms at both temperatures. All strains showed hemolytic activity against both human and sheep erythrocytes, but only a small subset of (6%) NOVC could survive in 60% human serum. In antimicrobial susceptibility tests, five NOVC strains developed non-wildtype resistance to antimicrobials across three different classes (penicillin, carbapenem, cephalosporin). In conclusion, this study characterized the virulence profiles of NOVC isolates from seafood and German coastal waters, highlighting the need for further monitoring and research.
Weniger anzeigenNeurodegenerative diseases (NDDs) encompass a heterogeneous group of chronic neurological disorders characterized by progressive neuron degeneration within specific regions of the central nervous system (CNS). Among these, Alzheimer's disease (AD) stands out as the most prevalent cause of dementia, accounting for approximately 60-80% of all dementia cases. Neuropathologically, AD is marked by the presence of two prominent protein pathological hallmarks: 1) the extracellular accumulation of aggregated amyloid-beta (Aβ) peptides, leading to the formation of amyloid-plaques, and 2) the intracellular aggregation of fibrillar structures composed of neuronal microtubule-associated protein Tau, forming neurofibrillary tangles (NFTs). Despite extensive and prolonged research efforts spanning several decades, the underlying molecular mechanisms of this intricate neurodegenerative condition remain only partially understood. In this context, the present study employs a well-established HEK sensor cell line, constitutively expressing the aggregation-prone mutant Tau repeat domain fused to either cyan fluorescent protein (CFP) or yellow fluorescent protein (YFP) (TauRDP301S-CFP/YFP). By introducing pre-aggregated Tau forms into these cells, a spectrum of distinct Tau assemblies is generated, encompassing large amorphous cytosolic aggregates (CYT) and amyloid-like structures (AMY), compact cytosolic Tau clusters (CLUS), Tau clusters near the nuclear envelope (NE), and nuclear spherical accumulations (NUC). After determining the sequence of accumulation type occurrence by live cell time-lapse imaging, I characterized the packing density of Tau in the different accumulation types using a multimodal microscopy approach. High-resolution FLIM/FRET microscopy, in which the fluorescent lifetime quenching of CFP serves as a proxy for the packing density of Tau, revealed distinct differences between Tau accumulations, as well as confirming a time-dependent hardening of Tau condensates in vitro. Optical diffraction tomography (ODT), which measures absolute protein concentration, revealed differences in the molecular and physical density of Tau accumulations. Additionally, it unveiled a drastic restructuring of 24-hour-old Tau 14 condensates compared to freshly formed 1-hour-old condensates, suggesting the potential transition from soluble Tau to fibrillar Tau aggregates. Lastly, 3D confocal reconstruction microscopy and StED microscopy provided insight into the precise positioning of different Tau accumulations regarding cytoskeletal fibers and cellular landmark organelles, such as the nuclear envelope and the endoplasmic reticulum (ER), revealing multiple interaction partners of Tau and implying possible downstream effects of Tau on cellular processes and mechanisms. By employing various light microscopy techniques, insights into Tau aggregation at different stages was gained, contributing to a deeper understanding of Tau aggregation formation and its implications for cellular processes. Furthermore, ODT emerged as a valuable tool for studying Tau aggregation in both cellular environments and in vitro conditions, revealing new structural insights. This research may offer prospects for understanding Tau transition and potential drug development.
Weniger anzeigenOur lab focuses on studying mobile genetic elements and their contribution to genome evolution. The remnants of mobile genetic elements can be repurposed by the host. For example, they serve as enhancers, alternative poly(A) signals, splice sites, exons, or entirely new genes. This study investigates the domestication of DNA transposons to form entirely new genes. PiggyBac-derived elements (PGBDs) are transposase-like genes that have been repeatedly domesticated into vertebrate genomes, suggesting that they may have important functions in host biology. The human genome comprises five PGBD genes, PGBD1-5. However, little is known about the molecular mechanisms underlying their domestication or their physiological roles. Therefore, we investigated the evolutionary history and possible molecular functions of the human PGBD family, especially PGBD1 and PGBD5, as an example of host transposase domestication events. First, we investigated the domestication event of PGBD1 and found that it had captured an N-terminal SCAN and KRAB domain in its ancestral condition. However, while the transposase domain was under strong evolutionary constraints, the N-terminal domains (NTDs) were under lesser purifying selection. In the KRAB domain that showed Ka/Ks ratios bigger than 1, amino acid substitution may have been beneficial for PGBD1 function, including 252M, which might have compromised Tripartite motif containing 28 (TRIM28) binding capacity. Additional losses and decays of the N-terminal domain of PGBD1 highlight the functional dominance of the domesticated transposase domain. Hence, host domains might facilitate the capture of DNA transposases to the host genome, but their function could be submissive to the protein function. In the second part, we investigated the molecular functions of PGBD5 and found that it is doubtfully an active transposase, and we identified that it interacts with another nuclease, topoisomerase II α (TOP2A). We show that PGBD5 is enhancing TOP2A function in-vitro and that it, together with topoisomerase II β (TOP2B), might regulate the transcription of a subset of immediate early genes (IEGs), namely FOS, NPAS4, NR4A1 and DUSP1 in the brain. Further, we show that PGBD5 interacts with several proteins involved in histone modifications, transcriptional regulation, and DNA repair. Altogether we provide an alternative mechanism by which PGBD5 contributes to DNA double-strand breaks (DSBs) and genomic rearrangements. Additionally, we show that PGBD5 adds an extra layer of IEG control that is specific to the brain and thereby contributes to brain-specific signaling. The thesis contributes to the knowledge of the molecular mechanisms underlying the domestication of transposase-like genes and their physiological roles in the host genome.
Weniger anzeigenThe development of flexible photovoltaic technology with low production costs is crucial for expanding access to solar energy and promoting its widespread adoption. One of the objectives of the CUSTOM-ART project (under grant agreement no. 952982) is to develop ultra-barrier films to protect photovoltaic cells using common, affordable plastic materials. To achieve this, the strategy adopted is based on the use of multi-nano-layer (MNL) polymer film co-extrusion technology aimed at orienting 2D montmorillonite nano-fillers dispersed in a poly(ethylene) matrix to produce films with a high degree of tortuosity. Therefore, this study focuses on characterizing the orientation of montmorillonite by systematic texture X-ray diffraction analysis. The results indicate that the orientation of montmorillonite with the MNL co-extrusion technology has a limited effect when the poly(ethylene) is in the molten state. However, the orientation is significantly improved with a biaxial stretching post-treatment of the films, which is performed at a temperature below the melting point of poly(ethylene). This raises the question of the influence of the matrix and the relationship between montmorillonite and poly(ethylene) on montmorillonite orientation. Further investigation of the crystallization of the poly(ethylene) phase revealed that it occurs around montmorillonite nano-fillers, allowing preferential orientation of poly(ethylene) crystals without affecting the rate of poly(ethylene) crystallinity. Consequently, the way poly(ethylene) crystallizes affects the orientation of montmorillonite. However, despite these variations in orientation, no significant improvement in the water barrier properties of the films was observed. Although the film has a controlled nanostructure, only 35% (including both montmorillonite and poly(ethylene) contributions) of the film consists of crystals, which may limit their ability to influence water diffusion through the films.
Weniger anzeigenThe oxygen reduction reaction (ORR) is a key limiting factor in fuel cell technology, driving extensive research efforts over the past few decades. Studies based on experiments and theoretical calculations on model single-crystal electrodes have helped establish fundamental trends across transition metal catalysts. In heterogeneous electrocatalysis, local electric field effects at the electrical double layer significantly influence the energies of reaction intermediates and impact catalyst performance in acidic or alkaline environments. However, these local field effects are challenging to model computationally and are frequently omitted. First, this work focuses on O2 adsorption as the initial step of the ORR to understand the role of the elec- tric field. The first part of the study focuses on the weak binding Au(111) metal catalyst surface, which favors the formation of hydrogen peroxide over water, with its activity strongly dependent on the (absolute) electrode potential. The underlying microscopic mechanisms remain unclear, likely involving key elementary reaction steps. We systematically enhance the double-layer model to clarify and compare the physical effects of the local field on O2 adsorption. This progression includes an applied saw-tooth potential in vacuum, an implicit solvent model, and explicit water modeling via ab initio molecular dynamics (AIMD). Two main contributions are identified to the potential dependence of O2 adsorption. Firstly, a dominant dipole- field interaction favors O2 binding going to reducing conditions across all models. Additionally, we observe stabilization from explicit H-bonding that can only be ob- served in AIMD, leading to a peroxo-O2* and a significant field response near the ORR onset. Since the O2* adsorption becomes favorable close to experimental ORR onsets and can explain experimental SHE-driven ORR activity, we predict that O2 adsorption is a potential-dependent, potentially rate-determining step of the ORR on the weak binding Au(111). These findings highlight the necessity of incorporating local electric field effects and explicit water in electrochemical interface models. Secondly, we draw a comparison to the more reactive Pt(111) surface. We conduct AIMD simulations to analyze and compare the properties of the metal/water interface Au(111) vs. Pt(111). Unlike Au(111), Pt(111) exhibits negligible potential dependence under realistic ORR conditions due to the inherently different reactivity of the two metals. We find a closely adsorbed peroxo O2* state with a relatively constant number of H-bonds, irrespective of the potential or surface coverage on the Pt(111). In contrast, the interfacial water structure on Pt(111) undergoes significant changes due to the inclusion of more realistic surface coverages and potential variations. In our set-up, we observe O2* dissociation determining the ORR selectivity towards H2O. We find an indirect effect of the potential through surface coverage: The O2* dissociation is promoted by desorption of H2O* at reducing conditions. Our overall results emphasize the importance of accounting for local field effects, which i) can directly impact reaction steps but ii) can also indirectly impact the reaction mechanism through a more complex interplay between potential, surface coverage, and water structure.
Weniger anzeigenThe formation, maintenance, and regeneration of skeletal muscle tissue depend on the interplay between muscle progenitor cells, known as myoblasts, and other local cell populations. Successful myogenesis requires precise regulation of multiple cellular processes, culminating in the formation of myofibers, multinuclear contractile syncytia from myoblasts. Proliferating myoblasts migrate to the muscle formation region, adhere to each other, express terminal differentiation markers, and eventually fuse their cytoplasmic contents. These processes are characterized by dynamic alterations in cytoskeletal architecture. The cytoskeleton comprises polymerizing proteins such as microfilaments, microtubules, intermediate filaments, and septins, forming an interconnected network of filaments. While the roles of actin, tubulin, and intermediate filaments are well studied, septins have only recently begun to emerge in the myogenic context. In my thesis, I investigated the expression and organization of septin paralogues in dividing and differentiating myoblasts, describing septins as a necessary component of the myoblast cytoskeleton. I propose the existence of septin octamers in myoblasts consisting of Septin2-7-11 and 9, with Septin9 undergoing substantial changes in expression. Septin9 mRNA is induced as quiescent cells transition to activated progenitors in regenerating mouse muscle and is downregulated by the end of the regenerative process. Septin9 mRNA and protein expression were also reduced during in vitro differentiation in C2C12 and primary myoblasts. Cycling myoblasts incorporate Septin9 into actin-decorating septin filaments that form primarily near the nucleus, in close proximity to the plasma membrane. However, these filaments undergo substantial reorganization after myogenic differentiation is induced. I observed that a fraction of Myogenin-positive cells exhibits short, curved septin rods and filament remnants, with no co-localization with actin filaments. This reorganization potentially coincides with the accumulation of muscle specific actin and myosin proteins. These findings were confirmed via live-cell microscopy using an endogenously tagged eGFP-Septin9 C2C12 cell line. Furthermore, nascent myotubes showed septin filaments extending across the perinuclear area in the basal plane, while the rest of the sarcoplasm contained filamentous remnants and rings. Mature myotubes, which exhibit sarcomeric actin organization, were mostly devoid of septin structures. SiRNA-mediated depletion of Septin9 resulted in the disruption of septin filaments and in a premature transition from proliferating to committed transcriptional signature in C2C12 and primary myoblasts, as evident from RNASeq analysis. Additionally, Septin9-deficient myoblasts showed signs of premature cell cycle exit, increased apoptosis, and a precocious onset of myogenic differentiation during in vitro differentiation. Taken together, my findings establish Septin9 as a critical regulator of myoblast differentiation during the initial commitment phase. We propose that filamentous septin structures are part of a temporal regulatory mechanism governing myogenic differentiation, with their reorganization marking the progress of unfolding myoblast differentiation.
Weniger anzeigenThe Varroa destructor parasitisation has remained one of the main causes for colony losses all around the world since the introduction of the mite in Apis mellifera populations. One of the natural defence mechanisms used by the honeybee in the fight against V. destructor is hygienic behaviour, particularly a specialized form of it – Varroa-sensitive hygiene (VSH) – which includes the uncapping and removing of parasite-infested, or dead brood. When infested, capped brood changes its cuticular profile sending an olfactory signal which only a few workers in the colony can sense. Subsequently, the brood cell is opened, and the mite removed. Hygienic behaviour and olfactory sensitivity to brood-related odours are observed to be strongly influenced by genetics. Breeding efforts with the goal of enhancing the European honeybee’s resilience have been ongoing for more than three decades, but to date no breeding strategy has reached a broad-scale host-parasite balance. Due to the strong environmental dependence of resistance traits, the reproductive and genetic peculiarities of the honeybee, as well the small-scale structure of the German beekeeping community, very labour-intensive traditional breeding programmes for this species are in need of transformation. Having this in mind, this project focused on the development of a new strategy that has the potential to make breeding in honeybees significantly more efficient by utilising drones’ olfactory as a selection trait. As drones are haploid, the genetic potential for Varroa-resistance can be assessed on the gametes. This allows genetic differences to be recognised significantly better and enables faster selection success. The proboscis extension response (PER) conditioning as a non-invasive method of observing olfactory sensitivity in both workers and drones enabled the gathering of insights into VSH and its inheritance and was chosen for the selection of the most suitable individuals. In a first step, workers bred for VSH and nonselected control line workers were tested via PER conditioning for differences in their speed and perception ability when presented with highly diluted stimuli. Two pairs of odours (Pair 1: citral as Cs+: linalool as Cs-; Pair 2: Varroa-parasitised brood extract as Cs+, isopropanol as Cs-) were used as tactile stimuli for the differential conditioning. Citral – a floral odour – and the brood extract were especially chosen in order to observe whether breeding for resistance in one of the tested groups had an effect on odour sensitivity to all or only to special odours connected to VSH. The VSH-selected line exhibited a significantly higher speed of perception for the parasitised brood extract than the nonselected line. The two lines showed no differences when conditioned with the floral stimulus citral as Cs+. The results suggested an increased specific sensitivity to chemical stimuli emanating from the brood in VSH-selected workers, which could play a role in recognising and removing V. destructor. In a second step, the odour sensitivity of drones to the Varroa-parasitised-brood extract was examined through PER conditioning. Sperm from drones, sensitive/insensitive to two Varroa-parasitised-brood odours concentrations was extracted, and queens from VSH-selected and nonselected lines were inseminated accordingly, following a mating scheme. The VSH behaviour of the offspring was observed, and the genetic origin of queens and drones as well as the drones’ perception of the brood odour were considered. While drone PER conditioning did not significantly correlate with VSH results, the genetic origin of participating queens and drones played a crucial role in VSH manifestation. A tendency for maternal effects for the inheritance of VSH was observed, suggesting that the choice of father drones would have less influence on VSH than that of mothers as genes connected to VSH are inherited via mitochondrial DNA of the mother. Additive genetic effects were also observed when drones from the VSH-selected line were paired with queens from the VSH-selected line, suggesting that drone’s genes nevertheless play an important role in resistance breeding. The role of the drone should therefore not be underestimated.
Weniger anzeigenThis dissertation aimed to evaluate passive behavioural data as a new data source in the field of public mental health. To date, research in the field of public mental health has primarily used written or oral self-report data as a method, which requires great effort, is time-consuming, and is susceptible to report bias. The conceptualisation of prevention measures and needs in the space of public mental health requires data that are as up-to-date and precise as possible. The use of smartphone-assessed passive behavioural data has already been discussed as additional objective measurement method to identify symptoms of mental disorders. Standardised parameters of passive behavioural data do not yet exist within the public mental health context. However, before passive behavioural data can be integrated as a new data source in the field of public mental health research, it must be evaluated on the basis of quality criteria. The evaluation of passive behavioural data is accompanied by essential ethical (and data protection) questions. Due to the currently high prevalence of depressive disorders worldwide and their tremendous individual and social consequences, the evaluation of passive behavioural data in the present dissertation was carried out by using depressive symptoms as the example. The three research projects in this dissertation were based on data collection aiming to predict depressive symptoms with the help of passive behavioural data. The results from Research Project 1 suggested that passive behavioural smartphone data offered added content value compared to survey data of established self-reported predictors of depressive symptoms. Of the included passive behavioural smartphone data, messenger use and video calls, as correlates of social interaction, contributed significantly to the prediction of depressive symptoms. The results of Research Project 1 suggested that passive behavioural data could be used as measures of depressive symptoms; a precise attribution of passive behavioural data points to individual depressive symptoms is still pending. This would enable continuous data collection in the public mental health sector and thus early identification of trends in the prevalence of depressive symptoms. This, in turn, provides the basis for the equally timely planning and implementation of preventive measures. In addition, Research Project 2 investigated the contribution of regional data derived from official statistics based on GPS location to the prediction of individual depressive symptoms. The results showed that regional information could be helpful in identifying risk groups in the public mental health sector. The results were not transferable to the postpandemic period due to the survey being conducted during the COVID-19 pandemic but, at the same time, provide valuable information on groups particularly at risk for depressive symptoms during a pandemic. Research project 3 investigated the extent to which characteristics of passive behavioural data are valid as correlates of depressive symptoms across individuals. To this end, we tested the extent to which personality facets and perceived social support were associated with the relationship between media use and physical activity levels (measured as behavioural data) and depressive symptoms. Some behavioural data points were found to be related to depressive symptoms independently of individual characteristics, while others were related to depressive symptoms in differential ways. Thus, the results of Research Project 3 highlighted the relevance of interindividual differences in the assessment of passive behavioural data. Overall, the results indicated that defining consistent behavioural data measures for the public mental health field is challenging, as some behavioural data measures show different strengths of associations with depressive symptoms between individuals. As a practical implication, both an individual-centred approach and the inclusion of person-specific control variables are recommended.
Weniger anzeigenThis thesis examines how cognitive and emotional individual differences predispose biased mindsets and suggestiveness in formal and informal questioning of children about child sexual abuse (CSA) suspicions. Across five empirical studies, presented in three articles, the Cognitions and Emotions about Child Sexual Abuse (CECSA) scales were developed, validated, and tested for their relationship to biased judgments and suggestive questioning, and for their responsiveness to training. Article 1 outlines the development and initial validation of three CECSA scales – Naive Confidence (NC), Emotional Reactivity (ER), and Justice System Distrust (JSD) – in a sample of 801 human sciences students. The scales demonstrated good model fit, acceptable to good reliability and, importantly, predicted participants’ bias toward the abuse hypothesis when judging vague CSA suspicions. Article 2 presents three mock case studies for predicting bias and suggestive questioning using varying formats for question posing: a single-choice format, a free-writing format, and a natural language format in a virtual reality (VR) simulation. Results for a total of 674 students from diverse disciplines (human sciences, teaching, police studies) showed that NC and ER, but not JSD, robustly predicted biased mindsets and a suggestive questioning style across the three studies and a meta-analytic integration. Article 3 evaluates a training program aimed at improving questioning techniques and related constructs. A secondary analysis of the data showed that a two-day seminar-style training significantly reduced NC and ER scores, while the results for JSD were inconclusive. These findings establish the CECSA scales NC and ER as reliable predictors of bias and a suggestive questioning style and show that both are modifiable through training. The scales are of diagnostic and evaluative value for training development or personnel selection, and can be used and extended to further investigate differential aspects of child sexual abuse investigations.
Weniger anzeigenPolitical regulations are an efficient instrument to reduce emissions, but developing mitigation strategies require information on the source contributions. Informations on local traffic emissions are usually available, but the contribution to the regional background is often missing. CTMs are widely used to assess the air pollution and support policy decisions. This study focuses on improving the quantification of the source contribution to the concentration levels of PM, NO2 and O3 in Germany. A source apportionment was performed to identify the most important sources for NOX in Germany and Berlin. Contributions to NOX were calculated using the labeling system in LOTOS-EUROS. Most important contributions to NO2 are road transport (~45 %), non-road transport (~24 %), energy & industry (~20 %) and households (~10 %). The impact of emission reduction was calculated using the brute force technique. Main differences between potential impacts (upscaling the impact to 100 %) and contributions were observed for ozone-limiting conditions. At night and in winter, the non-linear photochemical reaction between source sectors is often hampered and no regime change in the titration of O3 takes place. In the urban background, the sum of the potential impacts from each source sector overestimates the unperturbed baseline concentration for NO by about 50 % on annual average. For rural background sites, the overestimation is roughly 10 % lower. Larger overestimation was observed for hourly time series and small-sized source categories. For NO2, the attributed concentration from the brute force simulation is about 5 % lower close to emission sources than that of the labeling system. For larger cities, differences between the two calculations are about -15 %. The differences between both techniques increase with smaller NOX reduction. A 25 % reduction in NOX emissions was identified as the limit for application of the brute force technique. As prior research studies show similar deficiencies for PM, the source attribution for PM was performed using the labeling system. Combustion processes from residential heating (~30 %), industry & energy production (~19 %) and road-transport (~12 %) are the most important sources in Berlin. Agriculture and the boundary contribute about 12 % and about 14 % respectively on annual average. The remaining contribution is explained by natural emissions. Domestic sources from Berlin (~25 %) and Germany (~24 %) explain about a half to the annual average concentration. About 33 % originate from transboundary transport. The rest can be attributed to natural sources. For PM episodes in winter up to a third of the PM concentration originates from sources in neighboring countries further east. Seasonal variations were caused by emissions from residential heating and energy production, most important in winter. Agriculture is a large source of PM in spring and summer. Households (~53 %) and road-transport (~17 %) contribute most to the urban increment in Berlin. Road transport explains about 22 % of coarse material in urban background sites. Previous research studies show larger traffic contributions of up to a factor of 4 in summer. Incomplete reporting of non-exhaust emissions from road traffic and land management activities may partly explain the underestimation. Model simulations with COSMO-CLM were performed to downscale meteorological reanalysis from ECMWF to the national scale for Germany and were used for the first time as input data in LOTOS-EUROS. This paves the way for forthcoming modeling in Germany and to incorporate meteorological forecasts from DWD. The study shows improved statistics for meteorological conditions in Germany with COSMO-CLM compared to the lower resolved ECMWF forecasts. Simulations with the dynamic mixed-layer set-up show too high mixing from the planetary boundary layer to higher model layers in LOTOS-EUROS. Different turbulence parameterizations were used in COSMO-CLM, but show no clear indication to improve the mixing in LOTOS-EUROS. The pollutants stay closer to the surface when a larger number of vertical layers is used. The refined vertical layering improves the modeling with LOTOS-EUROS for Berlin and lowers the bias in the urban background, especially for cold and stagnating weather conditions in winter. Ammonium and nitrate responded most sensitive to the higher resolved vertical layering and show increased concentrations. Modeling of O3 with LOTOS-EUROS for Germany was evaluated with three other CTMs in a national scale multi model inter-comparison. The individual models often show lower model-measurement agreement and a lower statistical skill than the ensemble mean of all models, especially at night and for high ozone levels. A dynamic model evaluation was designed that compares modeled and observed concentration regimes for temperature and humidity. Room for improvement was identified to reproduce the O3 sensitivity to temperature, where a large spread was observed between the models. LOTOS-EUROS captures the regional build-up and removal of O3 for day-to-day and season-to-season variations, but underestimates the O3 sensitivity to temperature. Different sensitivities of O3 to temperature between rural and urban background sites and spring and summer are captured with LOTOS-EUROS. Detailing the emission inventories at national level, the integration of resuspended coarse material as an additional source and the use of the high resolved vertical layering are recommended for future modeling with LOTOS-EUROS. Contributions from the labeling system must be the first guess for emission reduction scenarios using the brute-force technique. The calculation of potential impacts must be avoided for NO and for small-sized emission categories. The implementation of the labeling system for O3 will allow to account for the contributions of O3 in Germany with LOTOS-EUROS. The dynamic evaluation must be expanded to longer timeframes and to other pollutants.
Weniger anzeigenUveal melanoma (UM) is a challenging cancer which is a rare type of melanoma. It originates from the melanocytes, which bear GNAQ/GNA11 mutations, localized in the ocular tract, and progress with a high risk of metastasis associated with poor prognosis and limited therapeutic options. When the primary cancer cells metastasize, the median survival is on average twelve months. There are two main UM subtypes differing by their genomic profile and metastatic properties in the literature. UMs with Monosomy 3 (M3) subtype which is characterized by the loss of chromosome 3 and BAP1 mutation are associated with a worse prognosis. UMs with Disomy 3 (D3) do not show the loss of chromosome 3 yet, they carry mutually exclusive EIF1AX or SF3B1 mutations and exhibit better prognosis. In contrast to the D3 subtype, the underlying reasons why the M3 subtype with BAP1 mutations are linked to very high metastatic risk within the disease mechanisms are not fully understood. The low tumor mutation burden of UM suggests a contribution of epigenetic components to the disease mechanism. BAP1 is a member of the Polycomb repressive deubiquitinase (PR-DUB) complex acting as a tumor suppressor and an epigenetic regulator. Given the relevance of BAP1 loss in UM, we hypothesized that repatterning in the epigenetic landscape and regulation might be affected by the absence of BAP1, causing novel TF interplay that contributes to reprogramming the cells towards malignancy. Thus, we compared the genome-wide patterns in BAP1 wild-type versus BAP1 mutant cases. Within this scope, this thesis aims to decipher the altered gene regulation networks investigating the effects of BAP1 loss in UM. We set out to model BAP1 loss in UM cell lines to better understand the molecular programs related to the subtype. Then, we investigated the differences between transcriptomic and epigenomic landscapes in an integrative manner. Our findings demonstrated that BAP1 predominantly binds to active regulatory regions, particularly transcription start sites and enhancers. Its binding influences the chromatin landscape and facilitates interactions with pioneering transcription factors TFAP2A and TFAP2C, which may contribute to transcriptional reprogramming observed in BAP1-deficient UM cells. Furthermore, the loss of BAP1 leads to aberrations in the histone landscape, including alterations in H3K4me3, H3K4me1, H3K27ac, and H3K27me3, as well as chromatin remodeling at functional genomic elements, accompanied by changes in chromatin accessibility.
Weniger anzeigenThe remarkable morphological diversity observed across the animal kingdom is a result of the evolutionary modifications of developmental processes. A striking example of such diverse morphologies is the tetrapod limb where profound phenotypic adaptations enabled species to colonize diverse terrestrial, aquatic, and aerial habitats. This organ thus provides a compelling model for examining the cellular mechanisms driving such diversification. Among mammals, powered flight evolved uniquely within the order Chiroptera, commonly known as bats. This remarkable ability is attributed to their wing structure, which is characterized by massively elongated digits connected by a specialized tissue membrane, the chiropatagium, a distinctive feature found only in this species. However, the molecular origins and the extent of developmental reprogramming necessary to achieve this dramatic morphological adaptation remain poorly understood. To address this, we employed comparative single-cell and functional genomics approaches to investigate limb developmental cell states in both mice and bats. Our analysis revealed a significant conservation of cell states and processes across species. In contrast to previous hypotheses, this also included the process of interdigital apoptosis, which typically eliminates interdigital tissue in species with separated digits. Through microdissection of embryonic chiropatagium and subsequent single-cell transcriptomics profiling of this tissue, we discovered that the chiropatagium originates from fibroblasts that are distinct from apoptosis-related interdigital cells. We furthermore revealed that these fibroblasts in the distal, autopodial limb region repurpose a developmental program otherwise found in the proximal limb. Genes expressed in this chiropatagium cell program showed enrichment in functions related to cell proliferation, migration, and extracellular matrix organization, highlighting the significance of these processes in wing development. Functional genomics and gene network analyses identified the developmental transcription factors MEIS2 and TBX3 as key regulators of this cell program. Importantly, ectopic expression of these genes in distal mesenchymal cells of transgenic mice led to the activation of genes linked to chiropatagium development. As a result, mutant limbs exhibited significant morphological changes, including increased cell number, enhanced extracellular matrix content, and retention of interdigital tissue. Lastly, the bat MEIS2 and TBX3 regulatory landscapes revealed significant differences in enhancer activity and 3D chromatin structure, suggesting species-specific genomic features that mediate their activity during wing formation. Altogether, our findings unravel fundamental molecular mechanisms underlying bat wing development and demonstrate how drastic morphological changes, such as the emergence of a wing, can arise from the repurposing of existing developmental programs.
Weniger anzeigenEukaryotic cells employ membrane-bound compartments to spatially organize their internal components. However, the recent discovery of biomolecular condensates, liquid-like structures not limited by a membrane, has emerged as a novel mechanism for cellular organization. These condensates often assemble by liquid-liquid phase separation (LLPS), a phenomenon in which an initially homogeneous liquid mixture spontaneously separates into two (or more) distinct liquid phases. LLPS is emerging as an important principle for understanding the organization and dynamics at the synapse and cellular pathology in neurodegeneration. For instance, synaptic vesicle (SV) clusters are shown to assemble via condensation of synapsins, a highly abundant family of synaptic phosphoproteins, and SVs. This thesis investigates the roles of α-synuclein, a protein involved in the SV cycle and implicated in the pathology of Parkinson's disease (PD), in modulating biomolecular condensates and their interplay with membrane-bound organelles. The first part of the thesis examines the contribution of α-synuclein to maintaining SV clusters. α-Synuclein enriches the liquid phase of SVs/synapsin, preserving their biophysical properties while maintaining high mobility. The results show that the presence of SVs enhances the condensation rate between synapsin and α-synuclein, indicating that SVs act as catalysts for synapsin condensate formation. Importantly, α-synuclein alone is unable to cluster isolated SVs under physiological conditions, emphasizing the importance of the synapsin/α-synuclein molar ratio in assembling functional and physiological condensates. The second part of the thesis focuses on understanding the aberrant LLPS process that leads to the formation of α- synuclein-containing protein aggregates, specifically Lewy bodies (LBs). LBs are associated with synucleinopathies like PD. By employing a minimal system comprising α-synuclein and synphilin 1, another protein implicated in PD, LB-like structures (LBLs) are recapitulated. Remarkably, synphilin 1 can independently form fluid condensates, while α-synuclein envelops these condensates, forming a core-shell structure resembling LBs. Additionally, LBLs disrupt the fibrillar actin network and accumulate membrane-bound organelles, leading to mitochondrial collapse and their accumulation at the interface of the aggregates. These observations highlight the connection between α-synuclein-driven aberrant phase separation and the formation of membrane-containing inclusions. Together, this thesis contributes to our understanding of the intricate dynamics and functional consequences of biomolecular condensates, specifically focusing on the role of α-synuclein in modulating their formation and interplay with membrane-bound organelles. The findings presented here deepen our understanding of the molecular mechanisms underlying neurodegenerative disorders, particularly PD, and pave the way for future research aimed at developing therapeutic interventions targeting these aberrant processes.
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