Elucidating the role of SHOX2 in atrial fibrillation using a patient-derived human induced pluripotent stem cell model

The sinoatrial node (SAN) is the primary pacemaker of the heart, where the pulse necessary for cardiac contraction arises to be propagated to the cardiac chambers via the cardiac conduction system. The transcription factor short stature homeobox 2 ( SHOX2 ) is essential for the development and function of the SAN, activating a transcriptional program for pacemaker development while suppressing differentiation towards working myocardium during cardiogenesis. Variants in the SHOX2 gene have been associated with atrial fibrillation (AF), the most common cardiac arrhythmia. However, the pathomechanisms behind SHOX2 dependent AF and the SHOX2 regulatory genetic network have not been fully understood. Until now, the impact of Shox2 deficiency has only been investigated in mouse or zebrafish animal models. Therefore, the aim of this thesis was to gain new insights from a human background and to investigate whether data obtained via animal models can be transferred to a human model system. At the beginning of this work, two induced pluripotent stem cell (iPSC) lines from two different patients with early onset AF were available, carrying a heterozygous single nucleotide variant either in the 3’UTR or in the coding region of SHOX2. A targeted correction of these variants had already been performed to generate isogenic control lines. First, I generated two homozygous SHOX2 KO iPSC lines from the available cell lines and validated them using several methods. Furthermore, I established and adapted previously published differentiation protocols to generate pacemaker and atrial cardiomyocytes (CMs) from iPSCs. To uncover variant specific changes in the two patient lines that contribute to the disease phenotype, I performed comparative profiling with their isogenic controls using gene expression analysis, single cell RNA sequencing and electrical phenotyping. Gene expression profiling of iPSC derived CMs confirmed several deregulated gene expression patterns known from animal models and uncovered additional dysregulation. Data from Single cell RNA sequencing revealed a possibly impaired differentiation capability and disturbed mitochondrial function in the patient cells. In CMs of the 3’UTR variant patient line, changed action potential characteristics were discovered, which notably could be attributed to differential ion channel expression. M ost strikingly, upregulation of the Na+ channel SCN5A led to an increased action potential upstroke velocity and amplitude, and upregulation of several K+ channels caused a shortened repolarization time observed in the patient line. Thus, novel disease mechanisms causing SHOX2 dependent AF as well as underlying molecular mechanisms and potential targets for adapted treatment strategies could be uncovered. Overall, the established human iPSC model and the differentiated cardiac cell types provide a valuable tool to further dissect the detailed molecular mechanisms of SHOX2 dependent AF in the future

Statistical Inference in Cosmology - From Parameters to Learnable Functions

Inference tasks on non-Gaussian posterior distributions are commonly approached using Markov chain Monte Carlo. We draw an analogy to canonical partition functions defined as Laplace transforms of the Bayesian likelihood and prior. This allows to derive analytical expressions for cumulants of the posterior. At second order, we recover the conventional Fisher matrix formalism. We find a closed formula for cumulants of weakly non-Gaussian posteriors. Additionally, we use this formalism to construct physically motivated convergence criteria with clearly defined target values based on virialization, equipartition, and thermalization of the Markov chain. We successfully validate these approaches using a dark energy model applied to supernova data. To speed up forward simulation we use physics-informed neural networks (PINNs). They provide fast and accurate predictions of the luminosity distance for a given choice of parameters. Using the same architecture we perform a model-independent, parameter-free reconstruction of the Hubble function. The PINN uncertainties are quantified using a heteroscedastic loss and repulsive ensembles. Continuing in the vein of fast simulations, we construct the parallelized inflation solver PARALLIZIS, based on the Madelung transformed perturbation equations. It provides a forward simulation from arbitrary inflaton potentials to the primordial power spectrum, while allowing for GPU parallelization

Living on the edge - the evolutionary history, edaphic adaptations and conservation prospects of the Cheddar Pink, Dianthus gratianopolitanus

The Cheddar Pink (Dianthus gratianopolitanus Vill., Caryophyllaceae) is an endangered, herbaceous perennial native to Central Europe, currently facing population decline. To understand its evolutionary history and biogeographic patterns, we sampled 130 populations and 1705 individuals across its entire distribution range, from southern France to Poland and the British Isles and used nuclear AFLP data, maternally inherited plastid haplotype variation, whole plastome sequence information, and cytological data. The absence of spatial genetic variation, the high rate of mixed plastid haplotypes, and the lack of spatial structure in the plastome tree suggest postglacial gene flow, favoring a scenario of once widespread distribution with secondary fragmentation. While AFLP data revealed a genetic division between southern and northern groups, plastid haplotype variation did not show clear biogeographic patterns but did highlight southwestern richness. Differences in bedrock type, calcareous in the south and siliceous in the north, coincide with AFLP groupings, suggesting edaphic factors may influence the differentiation and adaptation of D. gratianopolitanus. Genetic and cytological data strongly support the existence of refugia in southern France: Although clear evidence for a northern German/Czech refugium is lacking, the survival of now-extinct small populations in western Germany near Belgium, with subsequent expansion, is a possibility. A third genetic group in Baden-Württemberg, located in the contact zone between northern and southern groups, might result from survival in unknown refugia or represent a melting pot scenario. The colonization of the British Isles likely originated from French populations, specifically from the (Pre-)Alps, expanding through Belgium and into the Isles, as supported by genetic assignment and plastid haplotypes. To further investigate local adaptations, cuttings of D. gratianopolitanus from both calcareous and siliceous regions were cultivated and used in a reciprocal transplant experiment in the Botanical Garden in Heidelberg. After one year of growth on triassic shell limestone, porphyry, and serpentine soils, fitness parameters and leaf elemental composition were assessed. Additionally, flowering time and behavior were recorded for individuals from the entire distribution range, as well as D. gratianopolitanus subsp. moravicus cultivated in the Botanical Garden in 2022 and 2023, respectively. While the results revealed only small adaptations in elemental uptake they indicated that plants from calcareous bedrock invested more in vegetative growth, potentially enhancing vegetative reproduction and competitiveness on restricted limestone outcrops. In contrast, plants from siliceous origins exhibited higher flowering rates, promoting gene flow and faster colonization in more open habitats. Although a trend towards earlier flowering between 2013 and 2022/23 was observed, higher early spring and summer temperatures alone likely do not suffice to trigger the earlier flowering. In addition, eleven metapopulations originating from both calcareous and siliceous regions were analyzed using nuclear AFLP data and plastid haplotypes. The genetic structuring revealed varying patterns of connectivity and degrees of isolation, that could indicate either recent gene flow or remnants of past connections. Ecological niche modeling under current and future climate scenarios revealed that southern populations are more affected by drought stress, while northern populations are limited by minimum temperatures. The siliceous group displayed a broader climatic niche, while the more specialized calcareous group might be more vulnerable to climate change. Although current climatic conditions predict a wider suitable area than presently occupied, future scenarios indicate a significant reduction in suitable habitats, with a trend towards higher elevations and northern migrations. These findings underscore the need for conservation strategies that target all subpopulations, preserve genetic variation, and potentially re-establish dispersal routes to ensure the survival of this species

Barrieren der Inanspruchnahme von Unterstützungs- und Entlastungsleistungen für pflegende Angehörige und das Potenzial digitaler Technologien

Pflegende Angehörige (PA) übernehmen den überwiegenden Anteil der häuslichen Pflegearbeit. Dabei kann es sich neben der praktischen Pflege auch um organisatorische oder bürokratische Aufgaben handeln. Während die Pflege einer nahestehenden Person mit positiven Aspekte einhergehen kann, wie beispielsweise ein persönliches Kompetenzerleben sowie die Möglichkeit weiterhin Zeit mit der pflegebedürftigen Person (PB) verbringen zu können, werden von PA auch Belastungen beschrieben. Diese können physischer (z.B. muskuloskelettale Beschwerden) und psychischer (z.B. Ängste, depressive Symptomatik) sowie finanzieller und organisatorischer Form vorliegen. Dem Belastungserleben kann durch Ressourcen der PA entgegengewirkt werden. Dazu zählen neben der Erwerbstätigkeit auch der Erhalt sozialer Kontakte sowie eine regelmäßige Auszeit von der Pflege. Die Förderung dieser Ressourcen kann durch die Nutzung vorhandener Unterstützungs- und Entlastungsleistungen erfolgen. Während Beratungsangebote unterstützende und entlastend

Setup of a Reaction Microscope for the Cryogenic Storage Ring CSR and first Measurements

This thesis describes the setup of the first cryogenic reaction microscope, a new addition to the Cryogenic Storage Ring CSR. A technical description of the major components of the reaction microscope is presented. Selected results of the first experiments are discussed. The electron-photo-detachment from CH– was investigated as a proof-of-principle experiment of photo-electron spectroscopy. All visible features correspond to known transitions from the molecular ion to the neutral. The Si– + Ar collision is used as an example of a negative ion - neutral interaction. The process for electron loss with simultaneous target ionization is identified as a correlated interaction of target and projectile electrons. The cross section ratio, with and without simultaneous target ionization, was found to be an order of magnitude higher than expected. For positive ion beam, electron transfer from a He, Ne or Ar neutral gas target to a Ar+ projectile was investigated. Transitions into ground and excited projectile states could be identified for all targets. In addition, transfer target excitation for Argon target and electron transfer into metastable Ar+ states from Helium and Neon targets is seen. The projectile scattering angle is extracted by the momentum transfer on the recoil ion

Ritual Performance in the American Feminist Utopian and Dystopian Novel from the Twentieth to the Twenty-First Century

This thesis explores the significance of ritual acts in feminist speculative fiction as a lens through which to examine the construction of gender, power, and resistance in both utopian and dystopian contexts. Against the backdrop of socio-political developments since the beginning of the twenty-first century - marked by increasing attacks on women’s rights and growing global inequality - the resurgence of feminist dystopian narratives reflects a growing cultural unease about stalled progress toward gender equality. This context provides a compelling rationale for examining the renewed popularity of feminist speculative fiction in recent decades and the narrative functions of ritual therein. The analysis focuses on a selection of feminist speculative novels from the North American literary tradition, written over the span of more than a century. These texts represent a wide spectrum of feminist visions and fall into three broad categories: utopian, dystopian, and hybrid forms. A shared cultural background among the authors allows for a consistent comparative analysis grounded in ritual theory as developed in Western academic contexts. Drawing on theoretical concepts from ritual studies - particularly those related to performance, social order, and symbolic meaning - the thesis argues that rituals in these works function not only as mechanisms of control used by oppressive regimes but also as transformative and symbolic acts of resistance. Rituals surrounding themes such as gender roles, reproductive rights, family structures, and political participation are shown to play a central role in maintaining or subverting existing power relations. In dystopian narratives, ritual practices often reinforce hierarchical, patriarchal systems, while in utopian visions they can enable solidarity, agency, and the construction of alternative social frameworks. The methodological approach combines literary analysis with insights from gender theory and anthropology. This interdisciplinary framework highlights how feminist speculative fiction uses ritual as a structural and thematic device to critique dominant ideologies and to imagine new forms of community and identity

Structural and bio-functional analysis revealed the mechanism of γ-tubulin ring complex formation in C. albicans

Die Zytokinese ist ein wichtiger biologischer Prozess für die Zellproliferation. Die Mikrotubuli (MT) als Zytoskelettmitglied ist für die Zellmigration, Zellteilung und Zellpolaritätsbildung unverzichtbar. Daher ist die Untersuchung des MT-Nukleationsmechanismus unerlässlich. γ-TuRC ist sowohl für centrosomalen MTOCs (centrosomalen Microtubule Organizing Centers) als auch bei ncMTOCs (noncentrosomalen Microtubule Organizing Centers) die MT-Nukleationsvorlage in Zellen. In dieser Arbeit konzentriere ich mich hauptsächlich auf das ncMTOC-System in C. albicans (SPB (Spindelpolkörper)) und versuchen diesen biologischen Mechanismus zu verstehen. In dieser Studie ist es mir gelungen, in Zusammenarbeit mit der Gruppe von Dr. Stefan Pfeffer, zwei Kryo-EM-Strukturen der MT-Kernbildungseinheit in C. albicans zu erhalten, die neue Einblicke in das Verständnis der MT-Ausbildung in C. albicans lieferten. Der 3.6 Å γ-TuSC-Komplex ist ein Monomer und bildet eine Y-förmige Struktur aus, die in Zusammenarbeit mit Dr. Erik Zupa aufgeklärt wurde. Mit der Strukturanalyse und den Mutationsexperimenten fand ich eine Insertionsschleife in Spc98, die mit Spc97 interagiert und den γ-TuSC stabilisiert. Darüber hinaus implizierten die Untersuchungen unterschiedlichen γ-Tubulin-Positionen in C. albicans und Xenopus die für die Aktivierung des γ-Tubulin-Ringkomplexes in C. albicans erforderlich sind2, 3. Die andere Kryo-EM-Struktur ist der 3.6 Å γ-TuRC auf der zytoplasmatischen Seite des SPBs, der durch die Co-expression von γ-TuSC mit Spc72 und Stu2 erhalten wurde. Dieser Teil wurde in Zusammenarbeit mit Bram Vermeulen (Doktorand aus der Gruppe von Dr. Stefan Pfeffer) durchgeführt. Mit Hilfe dieser Studie fanden wir überraschenderweise heraus, dass das Spc72CM1 als Dimer an Spc97 bindet und die dimerisierten CM1-Motive für die Oligomerisierung von γ-TuSC und die Zellviabilität entscheidend waren. Darüber hinaus fand ich auch die N-terminale Region des CM1-Motivs, die mit dem benachbarten Spc98 interagiert, was ebenfalls wichtig für die Förderung der Oligomerisierung von γ-TuSC ist. Darüber hinaus habe ich erfolgreich bestätigt, dass die C-terminale Region von Spc72(291-599) für die Interaktion mit der Cterminalen Helix von Stu2(894-924) essentiell ist. Basierend auf den monomeren und oligomeren Strukturen von γ-TuSC bestätigten wir die entscheidende Rolle dimerer CM1-Motive bei der γ-TuSC-Oligomerisierung. Darüber hinaus lieferte die direkte Bindung zwischen Spc72 und Stu2 in C. albicans auch weitere Hinweise darauf, dass Stu2 über seine gebundenen α/β-Tubulin-Dimere auf der zytoplasmatischen Seite die Mikrotubulinukleationsaktivität von an γ-TuRC stimuliert. In Zukunft muss untersucht werden, wie Stu2 auf struktureller Ebene an das γ-TuRC bindet, um die Funktion von Stu2 im MT-Ausbildungsprozess zusammen mit γ-TuRC besser zu verstehen. Der MTAusbildungsmechanismus auf der Kernseite ist ebenso wichtig zu untersuchen

Feedback dynamics in mechanochemical matter

Non-equilibrium microscopic processes can drive macroscopic shape changes in soft materials. Feedback arises when such shape changes alter the geometry constraining the microscopic dynamics. Although such feedback is common in living materials, which can actively change their chemical composition in response to environmental signals, the underlying theoretical principles, and the resulting dynamical phenomena are not well understood. Motivated by biological cells exchanging shape-dependent signals at physical contacts, I investigated incompressible droplets adjusting their interfacial tensions in response to contact-dependent signals. I derived a minimal set of equations governing the macroscopic droplet states controlled by two dimensionless feedback parameters. I discovered that the droplet’s adaptive wetting properties give rise to rich dynamical phenomena, including regimes of multistability, symmetry-breaking, excitability, and self-sustained shape oscillations. For some configurations, the topology of the arising phase-space structures is analogous to Hodgkin-Huxley type neuronal models, allowing me to identify parallels between adaptive wetting dynamics and signal processing in neurons. Applying these theoretical results to experimental shape measurements from imaging data of zebrafish embryos, I found that the critical point arising from a shape multistability promotes the formation of boundaries between different developing tissues. Moreover, using fully data-derived contact-networks, I predicted cellular differentiation patterns driven by contact-dependent signaling in mechanosensory epithelia of zebrafish larvae. Together, this thesis provides new paradigms for physical signal processing through shape adaptation in soft active materials, and uncovers novel modes of self-organisation in the collective dynamics of biological tissues

Active repression of alternative cell fates safeguards hepatocyte identity

Cell identity plasticity is a normal and essential feature of cells during development, but is also a hallmark of diseases such as cancer. The mechanisms involved in suppressing inappropriate cell fates are poorly understood. Gene repression in terminally-differentiated cells is typically thought to be mediated by passive epigenetic silencing, such as through DNA methylation and repressive histone modifications. However, recent studies suggest that active repression by cell type-specific transcription factors may play an essential role in maintaining cell identity. MYT1L, a neuron-specific transcriptional repressor, has been shown to maintain neuronal identity by the inhibition of non-neuronal lineages. The observation that deficiencies in MYT1L may lead to diseases such as neurodevelopmental disorders and cancer demonstrates its important role in cell identity maintenance by inhibition of cellular plasticity. In this thesis, I investigate whether active, lifelong transcriptional repression of alternate lineages – or safeguard repression – is a general mechanism for cell identity stabilisation. Using computational prediction and direct cell reprogramming, I demonstrate that PROX1 safeguards hepatocyte identity by directly suppressing alternate lineage programs, hence demonstrating safeguard repression in a second cell type and germ layer. With single-cell transcriptomics analysis, I find that PROX1 robustly silences donor and alternative cell identities. I also show that PROX1 directly binds to promoters of key mesodermal transcription factors, including Prrx1 and Pparg, hence decreasing their chromatin accessibility and expression. In addition, repression of PROX1 target genes during hepatocyte reprogramming mimicked effects of Prox1 overexpression. On the other hand, Prox1 deletion or target gene activation permitted inappropriate gene expression. Finally, in a hepatocellular carcinoma mouse model, Prox1 overexpression prevented tumour initiation, reducing overall tumour load and extending survival substantially. Prox1 depletion in the same model induced cholangiocarcinoma-like morphology and gene expression, demonstrating the role of PROX1 in cell identity maintenance. These results show that PROX1 is a repressive safeguard of hepatocyte identity. They also support a model whereby continuous silencing of alternate lineage gene expression programs by safeguard repressors prevents cell fate plasticity, thereby maintaining cell identity

A cryogenic microscope for state detection of Be+ ions confined in an ultra-low noise environment

Optical frequency standards are some of the best characterized systems in physics these days. While optical transitions highly charged ions are excellent candidates for pushing the limits of laser spectroscopy at highest precision further, they require sophisticated quantum logic schemes to be cooled and interrogated. A novel superconducting quadrupole resonator is characterized to confine both, HCI and logic beryllium ion in an environment free of external electromagnetic noise. By utilizing atomic transitions sensitive to magnetic field fluctuations, the Meissner state of the resonator was investigated