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Analyzing Peri-Urbanization and Land-Based Livelihoods in Mankweng, Limpopo (South Africa): A Remote Sensing Approach towards a Strategic Framework for Sustainable Livelihoods
No full textThe thesis “Analyzing Peri-Urbanization and Land-Based Livelihoods in Mankweng, Limpopo (South Africa): A Remote Sensing Approach towards a Strategic Framework for Sustainable Livelihoods” examines peri-urban transformation and land-based livelihood dynamics in Mankweng and its surroundings in Limpopo Province, South Africa, using an integrated remote sensing and participatory framework. It combines four components: (1) ground truthing to support the interpretation of very-high-resolution satellite imagery and contextualize land-based livelihood practices; (2) object-based image analysis (OBIA) to classify land use/cover across the peri-urban landscape; (3) derivation of a spatially explicit land-based livelihood typology using landscape metrics; and (4) development of sustainable scenarios and adaptive transformation pathways informed by participatory stakeholder engagement, including women and institutional actors.
The spatial analysis is based on 0.3 m WorldView-3 imagery covering 200 km². A multi-level OBIA framework integrates object segmentation with systematic feature extraction and feature selection to enable robust class discrimination across heterogeneous peri-urban land cover. The workflow maps 38 detailed land use/cover classes, revealing pronounced spatial differences across the peri-urban mosaic. The resulting land use/cover map is used to derive landscape metrics that serve as spatial proxies for locally relevant livelihood characteristics. On this basis, the thesis identifies 14 land-based livelihood types that capture variation in land-use intensity, settlement morphology, and livelihood orientation across Mankweng and its environs.
Finally, spatial evidence is integrated with stakeholder-identified priorities and actions to formulate pathway-linked scenarios. The resulting adaptive pathway grid bridges system knowledge with participatory inputs to support planning and decision-making for sustainable land-based livelihoods in a rapidly changing former-homeland peri-urban setting.2026-02-1
FBRSL1-associated syndrome: Studies on molecular mechanisms and pathogenesis
No full textDeutsche ForschungsgemeinschaftThe FBRSL1-associated syndrome is a rare and complex congenital dysmorphic retardation
syndrome. To date, four patients have been reported carrying either heterozygous nonsense
or frameshift variants in the N-terminal region of Fibrosin Like 1 (FBRSL1). FBRSL1 is a largely
uncharacterized gene with several isoforms, however, it is suspected to play a crucial role in
embryonic development. In this work, key molecular functions of FBRSL1 as well as the
pathogenic impact of truncating FBRSL1 variants were examined. Protein-protein interaction
analyses showed an association of both the long and short N-terminal FBRSL1 isoforms with
microtubule filaments. Moreover, FBRSL1 was shown to associate with the microtubule associated dynein-dynactin-Nuclear Mitotic Apparatus protein (DDN) complex, which has a
critical function in spindle orientation during mitosis. Interaction studies further revealed an
association of FBRSL1 with the transcription factor Yin Yang 1 (YY1) and the Nucleosome
Remodeling and Deacetylase (NuRD) complex, indicating a regulatory role in gene expression.
Chromatin immunoprecipitation followed by sequencing (ChIP-seq) demonstrated that
FBRSL1 binds predominantly upstream of protein-coding genes such as the epigenetic
regulators Bromodomain and PHD finger containing 1 (BRPF1) and Lysine Acetyltransferase
6A (KAT6A). Subsequent expression analyses in patient-derived fibroblasts and blood
samples revealed that both target genes, BRPF1 and KAT6A, are significantly downregulated
compared to healthy controls, suggesting that truncating FBRSL1 variants result in a
dysregulation of their target genes. Furthermore, interaction studies demonstrated a direct
interaction of the short N-terminal FBRSL1 isoform 3.1 with the Splicing factor 3B subunit 1
(SF3B1). In addition, increased exon 4 skipping in Mouse double minute 2 human homolog
(Mdm2), a negative regulator of p53, was observed in fbrsl1-depleted Xenopus laevis embryos,
suggesting that loss of Fbrsl1 impairs the Sf3b1-mediated splicing. To provide a versatile
platform for in vitro disease modeling, human induced pluripotent stem cell (iPSC) lines
carrying nonsense patient FBRSL1 variants were generated using the clustered regularly
interspaced short palindromic repeats (CRISPR)/Cas9-based genome editing. The resulting
mutant iPSC lines were comprehensively characterized to ensure their suitability for
downstream applications. Using these FBRSL1 mutant iPSC lines and patient-derived
material, it was demonstrated by transcriptional analyses that the nonsense patient variants in
FBRSL1 show distinct susceptibilities to nonsense-mediated messenger RNA decay (NMD).
In conclusion, the findings of this work provide evidence for the multifaceted molecular roles
of FBRSL1 in the mitosis-related microtubule network, transcriptional regulation, and RNA
splicing. Furthermore, elucidating the underlying pathomechanisms of the FBRSL1-associated
syndrome sheds light on the origins of the complex malformation and neurodevelopmental
phenotype.2026-12-0
Novel Synthetic Routes to Polycyclic Compounds
No full textIn recent years, increasing the three-dimensionality of small-molecule drug candidates has attracted considerable interest, as higher saturation is associated with improved physicochemical properties and clinical success. Molecules enriched in sp³-hybridised carbon atoms offer three-dimensional architectures and stereochemical complexity, enabling more selective target interactions. Polycyclic frameworks further enhance these properties by providing conformational rigidity, potentially improving affinity and selectivity towards the desired target. Despite their significant promise, efficient and broadly applicable synthetic strategies for saturated polycyclic scaffolds remain scarce. This thesis addresses this challenge through the development of novel synthetic methodologies for strained and saturated polycyclic compounds, with a particular focus on bicyclo[2.1.1]hexane and cyclobutane scaffolds.2026-02-2
Development and Application of Camelid Single-Domain Antibodies for Live and Multiplexed Imaging of Synaptic Structure and Function
No full textOptical microscopy has become one of the most powerful tools in biology, allowing the visualization of cells, subcellular structures, and molecular interactions, leading to a number of groundbreaking discoveries. Since the invention of the first microscopes, a wide range of imaging techniques have been developed to satisfy the diverse experimental needs, from fixed sample imaging to live-cell observations. Due to the small size and the extremely high number of proteins involved in most biological processes, the two main goals in the development of microscopy have been to increase the maximally achievable resolution and to increase the number of simultaneously detectable targets.
Although the advent of super-resolution microscopy has revolutionized optical imaging by overcoming the diffraction limit and significantly increasing resolution, the selective and targeted labeling of proteins with minimal linkage error remains a major challenge. While fluorescently labeled antibodies provide a universal labeling strategy for many imaging approaches, their large size and biophysical properties limit both achievable resolution and multiplexing capacity.
In contrast, small monovalent binders such as nanobodies have emerged as valuable alternatives to classical antibodies. Their small size and monovalent binding enable stoichiometric labeling with minimal fluorophore displacement, significantly reducing linkage error. Compared to conventional antibodies, these affinity probes also exhibit excellent thermal stability, improved tissue penetration, and are well-suited for live imaging applications.
In this project, I developed and characterized several nanobodies targeting the essential presynaptic protein Munc13, and contributed to the validation of two anti-Synaptotagmin-1 nanobodies. These primary binders have become versatile tools for both super-resolution and live-cell imaging, contributing to a better understanding of the physiology and function of their target proteins.
In addition, I developed a novel labeling strategy that combines secondary nanobodies with the self-labeling HaloTag system to enhance the multiplexing capabilities of existing microscopy techniques through fluorescence lifetime imaging.2026-06-2
Establishing a human microglia model to evaluate novel therapies for multiple sclerosis progression
No full textDespite significant advances in the development of therapies for multiple sclerosis (MS), treating disease progression remains a major clinical challenge. MS progression refers to the accumulation of neurological disability independent of relapse activity and is driven by chronic neurodegeneration. Microglia-mediated inflammation has been implicated in the mechanisms leading to disease progression and neurodegeneration, making the regulation of microglial states a promising therapeutic strategy to slow the progression of MS. To elucidate the mechanisms underlying microglia-driven inflammation in MS and to support the development of disease modifying therapies for relapses, the use of in vivo animal models and animal-derived in vitro systems have been essential. However, the translational success of therapies targeting MS progression has been limited due to the absence of human-specific disease mechanisms and the inability of current models to fully recapitulate the pathological features of MS progression. Consequently, there is an increasing need for human-derived in vitro microglia models to more accurately investigate the therapeutic potential of drugs for the treatment of MS progression.
In this study, human induced pluripotent stem cells (hiPSCs) were used to generate hiPSC-derived microglia (iMG). Comprehensive phenotypic and functional characterization demonstrated that iMG reflect key microglial features relevant to MS progression, supporting their use as a physiologically relevant model to test therapeutics targeting microglia and finally disease progression.
One promising therapeutic strategy involves the inhibition of Bruton’s tyrosine kinase (BTK), a key modulator of Fc receptor (FcR)-induced pro-inflammatory microglial responses. Four BTK inhibitors, evobrutinib, remibrutinib, tolebrutinib, and fenebrutinib, have been evaluated for their effects on microglia, with tolebrutinib recently showing promising clinical results in reducing the risk of MS progression. However, differences in experimental design, models used, and dosages across these studies have complicated direct comparisons. To address this, the second part of this study systematically evaluated the efficacy of the BTK inhibitors in modulating microglial responses following FcR-dependent stimulation, using a standardized, side-by-side comparison in human-derived iMG. All investigated compounds influenced microglia activity, reducing the expression of molecules involved in antigen presentation and/or FcR-induced chemokine secretion. Notably, while evobrutinib and fenebrutinib required high concentrations to exert effects, remibrutinib and tolebrutinib were effective at lower doses. These findings highlight the potential of BTK inhibitors, particularly remibrutinib and tolebrutinib, to regulate microglial functions involved in pathogenic T cell activation and migration, offering a promising therapeutic strategy for MS progression.2026-07-3
Immortalized Primate Granulosa Cell Lines and Pluripotent Stem Cell-Derived Early Germ Cells: Towards Ovarian Follicles In Vitro
No full textAccess to primate ovarian tissue and mature oocytes is extremely limited, yet these resources are crucial for advancing both infertility treatment and fundamental research in reproductive biology. Conventional sources are scarce and subject to ethical and practical constraints. New in vitro strategies, particularly those using stem cells and immortalized somatic cell lines, are increasingly viewed as promising alternatives for generating functional gametes. In this study, we establish and integrate two complementary in vitro models to reconstruct the somatic and germ cell (GC) components of the primate ovarian follicle. First, we generated eight clonal immortalized granulosa cell (IGrC) lines from the common marmoset (Callithrix jacchus) to overcome the limited lifespan and donor variability of primary granulosa cells (GrCs). Our new IGrC lines retain key GrC identity markers (such as FOXL2 co-expressed with SOX9) and form characteristic intercellular junctions and hybrid epithelial-mesenchymal cytoskeleton of natural follicular GrCs. Notably, all clones demonstrated robust, long-term proliferation with bypass of senescence, while preserving lineage-specific features, including steroidogenic capacity in select clones. Functional assays revealed heterogeneity between the clones: a subset of IGrC lines maintained aromatase expression and hormone production (estradiol (E2) and progesterone (P4)) when stimulated by increased intracellular cAMP. At the same time, other lines show diminished steroidogenesis concurrent with a loss of gonadotropin receptor expression. Transcriptomic profiling confirmed that immortalization induces partial dedifferentiation by downregulating differentiated granulosa functions (e.g., FSHR, STAR, and INHBA/B) while upregulating cell-cycle, survival, and developmental regulators. IGrC clones clustered closely with primary cells, underscoring preserved somatic cell identity. In the second part, we directed human induced pluripotent stem cells (hiPSCs) toward a GC fate by BMP priming and overexpression of the germline-specific RNA-binding proteins DAZL and BOLL. This approach yielded primordial germ cell-like cells (PGCLCs) that organized into cystic structures and expressed early germline markers (BLIMP1, TFAP2C, SOX17, NANOS3), demonstrating successful PGC specification. Notably, the pluripotency state exerted a significant influence on differentiation outcomes. This was shown by the naïve-state hiPSC line demonstrating superior induction of GC fate and partial activation of meiotic gene expression when compared to primed-state hiPSC lines. However, according to the transcriptome data, all differentiations remained arrested at a pre-meiotic, oogenic stage. Due to the absence of KIT/KITLG and GDF9/WNT4 signaling axes as somatic support signals, induced GCs failed to progress into fully grown oocytes. This may have led to the downregulation of folliculogenic factors. Even with three-dimensional culture to provide a more sterically permissive microenvironment, germ-somatic coordination remained incomplete, leading to stalled follicle-like assemblies. Together, this work delivers a sustainable primate GrCs model and contributes to the advancement of human in vitro gametogenesis (IVG). Our findings highlight the necessity of re-establishing cross-talk between somatic and GCs for complete folliculogenesis and provide insights for future ovarian bioengineering and fertility preservation efforts.2026-09-2
Capturing exciton wavefunctions by time-resolved photoemission orbital tomography
No full textExcitons are realizations of a correlated many-body wavefunction, consisting of a Coulomb-bound electron and hole pair. They are the dominant excitations in semiconducting organic and low-dimensional quantum materials and thus of great relevance for optoelectronic applications and information technology. To unlock the full optoelectronic potential and to harvest and control exciton-mediated energy conversion pathways, a microscopic understanding of the exciton is crucial. Ultimately, this relies on access to the correlated exciton wavefunction, which has hardly been realized in experiments.
This thesis expands on the concepts of photoemission orbital tomography to gain unprecedented insight into the correlated wavefunction of excitons in organic semiconductors, 2D transition metal dichalcogenide heterostructures, and 2D-organic hybrid interfaces. This includes exciton localization, hybridization, charge and energy transfer, and ultrafast exciton formation and relaxation dynamics. Working with the prototypical organic semiconductor buckminsterfullerene C, time-resolved photoemission orbital tomography is employed to unravel the multiorbital electron and hole contributions to the correlated exciton wavefunction thereby elucidating the charge-transfer character of the excitons. The same concepts are then generalized to image the relative electron-hole distribution of the moiré interlayer exciton formed by charge-transfer in a WSe/MoS heterostructure and to identify and visualize a hybrid exciton bridging the PTCDA/WSe hybrid interface.
Aiming to access the exciton wavefunction with atomic resolution, this thesis presents a lab-based approach to image three-dimensional wavefunctions based on photon energy-dependent measurements, thereby paving the way for femtosecond three-dimensional photoemission orbital tomography. To this end, a highly efficient experimental approach based on an EUV pulse-preserving monochromator is combined with a data-driven algorithmic reconstruction. The power of this approach is demonstrated by the three-dimensional imaging of the frontier orbitals of PTCDA on an Ag(110) surface.2026-03-1
Establishing proximity-dependent protein labeling to investigate co-chaperone mediated effector secretion in Ustilago maydis
No full textThe complex process of protein folding within the endoplasmic reticulum (ER) of the corn smut fungi Ustilago maydis depends on the coordinated action of chaperone and their associated co-chaperone proteins. The unfolded protein response (UPR) is activated during ER stress and Dnj1 and Dnj2 co-chaperones are upregulated (Pinter et al., 2019). Dnj1 resides in the ER lumen and Dnj2 is predicted to be an ER transmembrane protein, both containing a functional J domain which is well known to interact with ER chaperones for proper protein folding. In U. maydis, the role of Dnj1 is studied to some extent but Dnj2 is fully uncharacterized. Here, we revealed that both Dnj1 and Dnj2 are required for full virulence of U. maydis and double deletion of Dnj1 and Dnj2 exacerbated the virulence compared to single deletions. Dnj1 was shown to physically interact with ER chaperone Bip1, to functionally interact with the lectin chaperone Calnexin (Cne1) and to mediate secretion of the Cmu1 effector (Lo Presti et al., 2016). The specific role in virulence of both Dnj1 and Dnj2 and how they contribute with overlapping or specific functions related to folding and processing of secreted effectors was so far unknown. To this end, we established proximity dependent labeling in U. maydis using two biotin ligases TurboID and UltraID to identify putative interaction partners and substrate proteins of Dnj1 and Dnj2. Under normal growth conditions, many proteins including central factors of the ER folding machinery were identified as proximally localized partners of Dnj1 and Dnj2. Only few secreted proteins were found in the closest proximity as the majority of secreted proteins and/or effectors are specifically expressed during the fungal-plant interaction. To induce expression of genes encoding secreted proteins in axenic culture, we overexpressed two master regulator transcription factors, Hdp2 and Biz1, leading to significantly increased expression of more than 40 % and of the whole secretome and more than 70% of the so-called second wave effectors, comprising all so far characterized effectors contributing to U. maydis virulence. In this strain background more than 80 secreted proteins were found to be enriched in Dnj1/Dnj2 BioID strains besides UPR core proteins, which were also found in normal growth conditions. Many of the secreted proteins were specifically enriched by either Dnj1 or Dnj2 and only few were enriched in both strain backgrounds. Hence, it is conceivable that Dnj1 and Dnj2 have specific sets of substrate proteins. However, both co-chaperones are centrally placed in a common set of core proteins of the ER folding machinery and were found in both Dnj1 and Dnj2 fusions as likely interaction partners. This strongly suggests a potential interdependent role for both proteins within the ER folding machinery and quality control.2026-08-2
Regulation of the telomerase
No full textTranscription is essential to transfer genetic information and to allow cell viability. Cells must control the resulting traffic of RNA polymerases (RNAP) by holding transcription into gene boundaries and prevent conflicts with other RNA or DNA polymerases, which threaten genome stability. Neverthe-less, transcription termination of RNAPII turns out to be not efficient but rather allows transcription termination and 3’ end processing at multiple sites at terminator regions. So called, alternative poly-adenylation gives rise to different same gene 3’ isoforms with different 3’ untranslated region (3’UTR) length. On the one hand, this imposes regulative potential as the length of 3’UTRs affects half-life, localization, folding and translational value of an mRNA. One the other hand, it increases the risk of polymerase conflicts. Modulators of alternative polyadenylation were heavily investigated as altera-tion can result in various diseases including cancer. However, the complex interplay of multiple fac-tors and complexes remains to be decrypted.
In this study we found an interplay between components of the two main transcription termination pathways in S. cerevisiae: mediated by the cleavage and polyadenylation and cleavage factor com-plex (CPF-CF) or the Nrd1-Nab3-Sen1 complex (NNS). We revealed that the scaffold RNA of the telomerase, TLC1, is terminated by the CPF-CF complex, however, is supported by Nrd1 and Nab3 binding at the terminator region, which serves a so far unknown function in NP-braking. Binding of Nrd1 and Nab3 upstream of the poly(A)-signal (PAS) slows transcription of RNAPII and, thereby, allows efficient formation of the CPF-CF complex at one specific PAS. This results in predominant presence of one 3’ isoform and efficient release of RNAPII from the DNA. In addition, the binding of Nrd1 and Nab3 serves as a guard-like quality control factor. CPF-CF formation on proximal sites releases both factors, however, if CPF-CF formation failed at these sites and occurs downstream, Nrd1 and Nab3 remain bound and mediate decay of these readthrough transcripts. Strikingly, we found that NP-braking is a more general mechanism for CPF-CF-mediated transcription termination, being present for ~25 % of mRNAs. NP-braking acts on genes with high risk of polymerase conflicts. In addition, it can result in preferential usage of the downstream PAS site and, thereby, can influence the 3’UTR length and the transcript fate. NP-braking might be a mechanism to ensure genome sta-bility by avoiding polymerase conflicts genome wide and might possess regulative potential under-lining its relevance in transcription termination.2026-08-2
Analysis of unconventional plant defence suppression by the signal peptide peptidase Spp1 in the Ustilago maydis - maize interaction
No full textIn the smut fungus Ustilago maydis, the signal peptide peptidase (SPP) Spp1 is essential for plant defence suppression and establishment of a compatible biotrophic interaction with its host plant maize. SPPs are endoplasmic reticulum (ER) resident intramembrane proteases, that are known to cleave remnant signal peptides as well as transmembrane domain (TMD) containing proteins, releasing them from the membrane for degradation or to exert a biological function. Catalytic activity is broadly conserved and crucial for the virulence function in U. maydis, however Spp1 substrates have not been identified.
Under axenic culture conditions, Spp1 is dispensable, whereas its transcriptional induction upon plant infection is directly regulated by the unfolded protein response (UPR), which is tightly interconnected with biotrophic growth in U. maydis (Pinter et al., 2019). In this study, the plant defence responses to U. maydis inoculation were dissected using transcriptomics, revealing a broad but distinct response upon inoculation with Spp1 mutant strains. Transcriptome analysis of the mutant strains during in planta growth revealed a growth delay compared to WT strains and significantly reduced appressoria
penetration efficiency of ∆spp1 strains. Spp1 expression needs to be dynamically regulated, with high transcript levels required throughout the whole biotrophic phase. Deletion of the UPR elements (UPREs) in its promoter abolished ER-stress and plant
specific spp1 induction, but basal levels were sufficient for in planta proliferation suggesting cell type specific regulation by a so far unidentified transcriptional regulator. Moreover, the presence of UPREs in spp1 ortholog promoters and their plant specific
induction seems to be conserved specifically in biotrophic fungi, hinting at a function of Spp1 in virulence exclusively of biotrophs. This was supported by the dispensability of Spp1 in the hemibiotroph V. dahliae and the requirement of Spp1 for virulence in the biotroph S. reilianum. Finally, potential substrates and interacting proteins of Spp1 were
identified using a Co-IP approach from inoculated plant tissue, identifying the SCSdomain containing protein UMAG_11696 as an important Spp1-associated virulence factor and the Rsp3 effector that requires Spp1 for proper processing, which was
previously shown to be required for its virulence function.2026-08-2