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Designing riboswitch-based gene control platforms for mammalian cells
No full textThe capacity to precisely control the timing, duration, and levels of gene expression is critical for better understanding and manipulating complex biological systems. Therefore, synthetic gene expression control devices are valuable in basic and applied research areas, including gene therapy, cell therapy, tissue engineering, drug discovery, and functional genomics. In this regard, artificial riboswitches have emerged as modular tools with advantages such as small size and low risk of immunogenicity. Riboswitch-based gene expression control systems incor-porate allosterically addressable RNA structures that can bind small molecules, namely apta-mers, into post-transcriptional control mechanisms to regulate gene circuit behavior, namely the expression platforms. However, while there are naturally occurring examples in bacteria and de novo applications in the cell-free context, riboswitch-enabled gene expression control applications for eukaryotic systems have been limited.
In the first part of the thesis, a novel expression platform for the tetracycline-responsive apta-mer was developed to regulate gene expression at the translational level. The developed plat-form is based on -1-programmed ribosomal frameshifting, a mechanism that is essential for the post-transcriptional regulation of gene expression in several organisms. By placing the apta-mer as a stimulatory structure on the -1 PRF platform, a switch has been constructed that enables robust induction of gene expression upon tetracycline addition. By varying the precise spacing and composition of the tetracycline aptamer and adapting -1 PRF modules from se-veral viruses, the characteristics and optimal frameshift layout for the tetracycline-inducible platform were characterized. Furthermore, dose-response analysis showed that the tetracyc-line-inducible -1-PRF platform has improved sensitivity at concentrations that fall within the clinically approved window. Next, a compact and modular tetracycline-inducible -1-PRF plat-form was developed by integrating accessory elements. Finally, the efficacy of the platform in various genetic contexts was confirmed by testing in different transcription units and cell lines and by controlling the production of therapeutically relevant genes.
In the second part of the thesis, we aimed to expand the potential applications of mammalian exon-skipping riboswitches. Cis-regulatory elements on the mRNA are shown to be integral for refining outcomes of alternative splicing. By incorporating splicing-modulating G-quadruplexes into the splicing cassette, we have exploited these elements to fine-tune alternative splicing outcomes in exon-skipping riboswitches. Our work led to the improvement of the dynamic ran-ge in a number of different tetracycline-inducible exon-skipping riboswitches. Furthermore, we devised a method to convert the splicing-based ON switch to an OFF switch by integrating inhibitory competitor RNA structures into the splicing cassette, thereby enhancing the versatili-ty of the splicing-based switches. Lastly, we altered the splicing cassette to be readily incorpo-rated into the major late transcription unit of oncolytic adenoviruses. In our approach, an intron from the splicing cassette was first modified to be controlled by the essential splicing compo-nents of viral origin. As a next step, a series of tetracycline riboswitches were designed to mo-dulate gene expression by controlling the accessibility of these viral splicing elements. Collec-tively, the three design strategies discussed in this section have improved riboswitch perfor-mance and effectively exploited the modular "plug-and-play" features of riboswitches in mammalian systems.
The systems presented in this thesis broaden the toolbox of genetic devices that can externally regulate gene expression with small molecules. The highly sensitive tetracycline-inducible -1-programmed ribosomal frameshifting platform developed in this study provides effective regu-lation at very low inducer concentrations and operates at the translational level. These features are particularly relevant for RNA-only therapeutic approaches and make these switches poten-tially compatible with therapeutic applications targeting diverse tissues. In addition, the opti-mization strategies described in this work could increase the practical value of artificial ri-boswitches in synthetic biology and enable new approaches to gene therapy.publishe
Typisierung von Bootsstationierungsanlagen (BoStA), ihrer Struktur- und Ausstattungselemente : Bericht der Arbeitsgruppe Umweltphysik am Limnologischen Institut der Universität Konstanz für das SuBoLakes-Projekt der Deutschen Bundesstiftung Umwelt (DBU), Az. 35825/01
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On the wrong track? : Perceived track mismatch among ethnic minority and majority students in the German education system
No full textThis paper explores why ethnic minority students are more likely than majority students to believe that they should attend a higher educational track. Based on a survey of seventh-grade students in Germany, we examine two explanations for this “perception gap.” First, minority students may be more likely than majority students to be placed in a track that is too low for them (“exposure” to unfair treatment). Second, minority students, who are more frequently enrolled in the lowest educational tracks and are often the children of highly ambitious parents, may feel a greater need to attribute limited educational success to unfair treatment in order to protect their self-esteem (“ex-post rationalization of a lack of success”). We find little evidence for the “exposure" mechanism. Instead, the “perception gap” between majority and minority students largely reflects their more frequent enrollment in the lowest, stigmatized track of the education system and their parents' high, unmet educational aspirations.publishe
Sideband attraction via internal resonance in a multimode membrane as a mechanism for frequency combs
No full textWe explore self-induced parametric coupling between a driven (low frequency) and an undriven (high frequency) mode, also called internal resonances, in a membrane micromechanical system. Specifically, we focus on the formation of a limit cycle (LC) manifesting as a phononic frequency comb. As the LC formation involves a Hopf bifurcation, we developed a dedicated pump-noisy-probe technique to investigate which mechanical sidebands merge at the bifurcation. We reveal that the sideband of the driven lower mode is up-converted via a cross-Duffing nonlinearity to hybridize with the undriven high mode. When the up-conversion is initially red detuned relative to the high mode, significant squeezing and bimodality in the high mode occurs. Crucially, only when the up-converted sideband is initially blue detuned relative to the high mode, the sideband is attracted to the high mode and merges to form the Hopf bifurcation. This process delineates the microscopic origin of frequency comb formation. Our study reveals a key instability mechanism in driven nonlinear systems with implications for advanced sensing technologies and phononic metamaterials.publishe
Female Motivation to Lead : The Impact of Same-Sex Role Models and Female Leadership Strength Awareness
No full textIntroduction Research on motivation to lead (MTL) suggests that women tend to be less motivated to take on leadership positions than men. By investigating female motivation to lead, we want to contest this finding. Methods We used five samples for validating our newly specified constructs (i.e., prosocial MTL and female leadership strength awareness) in Study 1 and a further sample of 248 students in Study 2. Results First, we propose a reconceptualization of MTL by introducing prosocial MTL as a fourth MTL type. We demonstrate that women have higher levels of prosocial MTL and non-calculative MTL, while men have higher levels of affective-identity MTL and social normative MTL. Second, we show that women are more strongly motivated to lead if they (a) have same-sex role models and (b) are aware of female strengths in leadership. Discussion We conclude that female motivation to lead is not necessarily lower than male motivation to lead but rather different in nature, and that it can be further enhanced by factors that seem particularly relevant for women.publishe
The stability and modulation of if-then rules versus prospective planning in movement selection under dual-tasking conditions
No full textTwo approaches to movement selection, if-then rules versus prospective planning, were investigated. Studies have shown that the rule-based approach leads to more efficient movement selection than the plan-based approach, though the resulting movements are the same. This dual-tasking study investigates two hypotheses explaining this discrepancy: The efficiency hypothesis states that the rule-based approach to movement selection is more efficient, and its advantage over the plan-based approach increases under any kind of enhanced task demands. The dual-mechanisms hypothesis states that the two approaches to movement selection are based on distinct mechanisms and that they can be differentially affected by secondary tasks. Forty-eight participants selected a grip in order to comfortably rotate a dowel to a target position using the rule- or the plan-based approach. Four dual-tasking conditions were added: Identifying the activity underlying an object-interaction sound, identifying and categorizing the object underlying an object-interaction sound, identifying one of four words that does not match the others semantically, and solving calculations. The rule-based approach led to more efficient movement selection in most dual-tasking conditions. However, its advantage disappeared when the secondary task was to identify and categorize objects. These results strengthen the dual-mechanisms hypothesis, and possible factors distinguishing the approaches are discussed.publishe
Human presence shifts the landscape of fear for a free‐living mammal
No full textHumans may play a key role in providing small prey mammals spatial and temporal refuge from predators, but few studies have captured the heterogeneity of these effects across space and time. Global COVID‐19 lockdown restrictions offered a unique opportunity to investigate how a sudden change in human presence in a semi‐urban park impacted wildlife. Here, we quantify how changes in the spatial distributions of humans and natural predators influenced the landscape of fear for the California ground squirrel ( Otospermophilus beecheyi ) in a COVID‐19 pandemic (2020) and non‐COVID (2019) year. We used a structural equation modeling approach to explore the direct and indirect effects of human presence, predator presence, and habitat features on foraging that reflected fear responses (e.g., giving‐up densities [GUDs], number of foragers, and average food intake rate while at food patches). In 2019, humans and dogs had moderate effects on GUDs; squirrels were less fearful (lower GUDs) in areas frequently visited by humans and dogs, but the effects of raptors were weak. In contrast, in 2020, the effects of humans and dogs on GUDs were weak; squirrels were more fearful of high raptor activity, open sky, and ground cover. In both years, squirrels farthest from refuge were the most risk‐averse. Overall, our analyses revealed an increase in perceived risk from natural predators in 2020 associated with a change in the concentration of human presence. Thus, risk‐sensitive foraging was dynamic across space and time, depending on a complex interplay among human and dog activity, natural predators, and microhabitat features. Our findings elucidate the myriad ways humans directly and indirectly influence animal perception of safety and danger.publishe
Localized Light-Induced Precipitation of Inorganic Materials
No full textThis perspective is dedicated to the memory of Prof. Dr. Helmut Cölfen.
The light-induced control in the fabrication of materials is a field in continuous development. So far, photo-induced processes have been used mostly for organic polymeric materials. However, there is a recent, increasing interest in exploring the possibility of using these techniques to induce the precipitation of inorganic materials. This perspective paper outlines the main principles of the light-induced precipitation of inorganic materials, focusing on the recent papers published in this field. The description of the mechanisms and the materials involved in these light-induced processes highlight their many possibilities and future challenges, which could pave the way for significant advancements in this exciting technology.publishe